Safflower Oil

“A pale, slow-drying, vegetable-based oil extracted from the seeds of the safflower plant (Carthamus tinctorius). It is commonly used as a binder in oil paints and as a medium ingredient due to its lighter color and lower tendency to yellow over time compared to linseed oil.

Chemically, safflower oil contains a higher proportion of linoleic acid (a polyunsaturated fatty acid) and a lower proportion of linolenic acid compared to linseed oil. As a result, even under ideal conditions, safflower oil oxidizes and polymerizes more slowly, forming a softer, less resilient film than linseed oil. This slower oxidation contributes to extended drying times and increased sensitivity to mechanical damage in finished paint films.

In oil painting, safflower oil is often favored for whites, light blues, and other delicate hues where color stability is critical. Its slow drying behavior facilitates blending and wet-on-wet techniques but requires careful management to avoid layering problems or surface vulnerabilities. Due to its softer film characteristics, safflower oil is generally recommended for upper paint layers rather than underlayers, aligning with traditional ‘fat over lean’ principles.

Best practices recommend using safflower oil strategically, balancing its advantages in color retention and blending flexibility against its mechanical limitations to ensure the long-term stability of the artwork.”

Sanding Block

“A handheld tool consisting of an abrasive surface mounted to a rigid or semi-rigid block, used to achieve controlled and uniform abrasion across a surface. Sanding blocks may be manufactured from solid materials (such as rubber, plastic, or wood) or created by wrapping sandpaper around a block or sponge.

In visual art and material preparation, sanding blocks are commonly employed to smooth rigid supports (such as wood panels or hardboard), level ground layers, modify surface textures, or prepare substrates for subsequent media application. Using a sanding block provides more even pressure and surface contact than sanding by hand alone, reducing the risk of creating gouges, inconsistent surfaces, or unintended distortions.

Artists also use sanding blocks to sharpen and refine the tips of dry media tools, such as charcoal sticks, pastel pencils, or graphite rods, enabling greater precision, line control, and surface responsiveness. Different abrasive grades (grits) allow for fine control over both surface refinement and tool sharpening.”

Sandpaper

“An abrasive material consisting of a flexible backing (such as paper, cloth, or synthetic film) coated with bonded abrasive particles used for controlled surface abrasion. The abrasive particles may be made of natural materials (such as garnet) or synthetic compounds (such as aluminum oxide, silicon carbide, or zirconia alumina), depending on the intended application.

Sandpaper is graded by grit size, which refers to the density and coarseness of the abrasive particles. Lower grits (e.g., 40–80) indicate coarse abrasion for rapid material removal, while higher grits (e.g., 400–1200) allow for fine surface refinement and polishing.

In visual art and material preparation, sandpaper is employed to smooth rigid supports, level ground layers, modify surface absorbency, refine surface texture, and sharpen dry media tools. It provides artists with precise control over surface characteristics critical to perceptual training, material handling, and structural preparation. Proper grit selection enables targeted surface modification without introducing excessive damage, irregularity, or disruption of material behavior.”

Saturation

“The perceived intensity or purity of a specific color in relation to its brightness. It determines how vivid or muted a color appears, with highly saturated colors appearing rich and intense, while desaturated colors appear washed out or grayish. Saturation is a relative measure, meaning it is influenced by lighting conditions, brightness levels, and surrounding colors, distinguishing it from absolute color attributes like chroma.

Saturation, intensity, and chroma (often used synonymously) all describe aspects of a color’s vividness, but they differ in how they are measured and perceived.

Distinction from Chroma and Intensity: Chroma is an absolute property that measures how much a color departs from neutral gray at the same value level. It remains stable across different lighting conditions. Saturation is a relative property that depends on a color’s brightness and surrounding context. A color’s saturation may appear different under various lighting conditions, even if its chroma remains unchanged. Intensity refers to how vivid or dull a color appears when mixed with other colors. Unlike chroma, intensity can be reduced by intermixing with neutral tones or complementary colors, making it a critical factor in paint mixing and practical color application.

While chroma defines color strength as an absolute measure, saturation describes how colorfulness is perceived relative to brightness, and intensity specifically refers to how strong a color remains in an intermixture.”

Savanna Hypothesis

“An evolutionary theory proposing that human beings possess innate aesthetic and emotional preferences for landscapes resembling African savannas—the environment in which early hominids are believed to have evolved. According to the hypothesis, open spaces interspersed with clusters of trees, distant views, and the availability of both refuge and resources are environmental features that humans are biologically predisposed to find attractive or comforting.

The concept originated in environmental psychology and evolutionary biology during the late 20th century, notably advanced by researchers such as Gordon H. Orians (1980s), who suggested that preferences for certain visual patterns in landscapes—such as scattered trees, open spaces, and water sources—reflect adaptive survival strategies developed on the East African savannas. These landscapes offered critical advantages: visibility for predator detection, access to food and water, and available shelter.

In visual art and landscape design, the Savanna Hypothesis has been used to explain recurring compositional strategies that emphasize open foregrounds, midground focal points (such as solitary trees or water bodies), and expansive, navigable vistas. It also informs research in neuroaesthetics and visual preference studies, suggesting that some compositional choices resonate with deep-seated evolutionary biases rather than purely cultural conditioning.

While influential, the hypothesis remains a subject of ongoing debate, particularly regarding the degree to which aesthetic preferences are universal versus shaped by cultural, developmental, and environmental factors.”

Scaffold

“As a noun, a scaffold refers to a temporary structure that provides external support during the development, construction, or learning of a more complex or independent form. In educational contexts, scaffolds are instructional supports that assist learners in acquiring new skills or concepts by breaking down complex tasks into manageable components.

As a verb, to scaffold means to provide graduated, provisional support that enables an individual to perform a task or develop a skill that would be beyond their unaided capabilities. As proficiency increases, the scaffold is gradually removed, allowing for independent execution.

In perceptual training and artistic skill development, scaffolding often takes the form of schematic construction methods, structured value organizations, progressive rendering exercises, or external aids such as grids and reference markers. These supports temporarily assist in organizing perceptual information, motor planning, and conceptual understanding until the learner internalizes the necessary competencies.

Unlike an armature, which serves as a persistent internal framework intended to remain integral to the final work, a scaffold is specifically designed to be transitional, supporting the learning or construction process without becoming a permanent part of the completed structure.”

Scaffolding for Visual Understanding

“A pedagogical approach in which foundational visual concepts—such as line, shape, and value—are introduced sequentially, allowing for the structured acquisition of more complex artistic skills. This method is based on cognitive load theory and Vygotsky’s Zone of Proximal Development, ensuring that students engage with new concepts at an optimal difficulty level before advancing. In visual arts, scaffolding can include progressive exercises in form-building, perspective, and color theory, gradually reinforcing perceptual and motor skills.”

Schematic

“A schematic refers to a simplified, organized representation of a subject designed to clarify functional, spatial, or compositional relationships without emphasizing fine surface details or full visual complexity. Schematic constructions prioritize clarity, proportion, and structural coherence, serving as foundational frameworks for more developed or refined work.

In perceptual training, such as the form repetition exercises within the Waichulis Curriculum, schematics are used to establish consistent configurations, directional flows, and proportional relationships before more complex surface information (such as texture, atmospheric modulation, or nuanced value transitions) is introduced. Schematic stages allow learners to focus on core structural behaviors—such as curvature integrity, spatial centering, and volume anchoring—without being overwhelmed by secondary visual variables.

Schematics differ from fully rendered representations in that they intentionally abstract or omit fine detail to prioritize the internal organization and perceptual anchoring of the subject. In both learning and professional practices, effective schematic construction facilitates efficient skill acquisition, surface control, and compositional planning.”

Schematic Substitution

“The unconscious replacement of observed visual information with pre-existing conceptual or symbolic representations stored in long-term memory. This often occurs when perceptual input is degraded, brief, or ambiguous—prompting the brain to ‘fill in’ missing information based on prior experience or generalized categories rather than direct visual observation. In the context of drawing and painting, schematic substitution can result in symbolic distortions, such as idealized or oversimplified depictions of forms (e.g., ‘almond eyes’, ‘lollipop trees’, or perfectly symmetrical faces) that conflict with what is actually seen.

Within the Waichulis Curriculum, schematic substitution is treated as a perceptual error pattern that must be recognized and actively managed. It is especially likely to emerge when observation time is limited or inconsistent, iconic or visual short-term memory (VSTM) resources are overtaxed, the learner fixates on the identity of the subject (‘what it is’) rather than the appearance of the subject (‘what it looks like’), or cognitive load is high, prompting the brain to rely on familiar conceptual templates.

The curriculum addresses schematic substitution through close proximity of reference and drawing surface to reduce reliance on memory, training exercises like Shape Replication and Gradation Patterns that require continuous perceptual calibration emphasis on perceptual properties (value, shape, proportion, edge) over, and the development of procedural fluency to reduce the likelihood of reverting to interpretive shortcuts under cognitive strain.

While schematic substitution is a natural product of the brain’s pattern-recognition systems, it poses a significant obstacle to accurate representational work if left unchecked. Awareness of this tendency—and the perceptual strategies used to override it—is essential for maintaining fidelity to observation and avoiding the intrusion of generalized memory templates during visual decision-making.”

Scotopic Vision

“Low-light (night) vision, primarily mediated by rod photoreceptors, which are highly sensitive to light and optimized for dim environments. While scotopic vision provides excellent light sensitivity, it has reduced visual acuity and severely limited color perception, as rods do not differentiate between long, medium, and short wavelengths the way cones do. However, rods exhibit peak sensitivity in the blue-green spectrum (~498 nm), meaning that under extremely dim conditions, some hues—especially bluish tones—may be perceived with greater prominence. Scotopic vision functions in darkness, transitioning to mesopic vision in moderate lighting, where both rods and cones contribute, and ultimately to photopic vision in bright conditions.”

Scribble / Scribbling

“The spontaneous, often unstructured application of marks without deliberate control over form, proportion, or perceptual organization. It is typically characterized by rapid, repetitive, or erratic movements that prioritize energetic expression or motor activity over precise representational intent.

In early developmental stages (such as child drawing behavior), scribbling represents an important exploratory phase, allowing individuals to develop motor coordination, spatial awareness, and early symbolic experimentation. In certain artistic practices, particularly within expressive or gestural drawing traditions, controlled forms of scribbling may be intentionally used to evoke dynamic energy, texture, or emotional resonance.

However, in contexts that emphasize perceptual precision, structural coherence, or material control—such as the Waichulis Curriculum’s perceptual training framework—scribbling is generally discouraged. Uncontrolled mark-making can interfere with the accurate calibration of pressure, curvature, value modulation, and spatial structuring critical to skill development. Instead, deliberate, systematic mark-making strategies are prioritized to reinforce consistent perceptual anchoring and motor control.

Scribbling should thus be distinguished from exploratory gestural mapping or schematic construction, which, while sometimes loose or energetic in appearance, retain an underlying intentional organization aligned with perceptual goals.”

Scumbling

“A specific indirect painting technique in which a thin, semi-opaque layer of paint is lightly dragged or scrubbed over a dry or semi-dry surface using a dry or lightly loaded brush. The resulting effect is a soft veil or atmospheric modulation that partially conceals and interacts with the underlying layer, subtly modifying value, hue, or surface cohesion.

Traditionally, scumbling referred to the application of lighter or white pigments over a darker layer to create a lifted, luminous haze—particularly evident in sky passages, flesh modeling, or atmospheric veiling in historical oil painting. Ralph Mayer describes it as a form of thin opaque application distinct from glazing (which is transparent), and often applied with rags, dabbers, or brushes to create a broken visual texture.

While historically linked with light-over-dark, contemporary usage acknowledges scumbling as a perceptual blending tool that may include a broader tonal range, not limited to light pigment alone. Its defining feature remains the broken, semi-opaque veil and its intent to modulate rather than fully obscure.

An important distinction between the concept of ‘dry-brush’ and scumbling is that scumbling utilizes dry-brush application, but not all dry-brush applications are scumbles. Scumbling specifically aims to modulate visual transitions and integrate layers atmospherically, whereas dry-brush may focus on texture articulation or edge control.

In the Waichulis Curriculum, scumbling is employed as part of indirect layering strategies to refine form transitions, atmospheric cohesion, and surface modulation.”

Secondary Light Source

“Any additional origin of illumination within a visual field or pictorial composition that influences form, value relationships, or atmospheric behavior without serving as the dominant structural anchor. Secondary sources may include reflected light, fill light, ambient illumination, or intentional secondary emitters within a scene.

In the Waichulis Curriculum, secondary light sources are treated as subordinate variables: they can enhance form visibility, introduce subtle value variations, or enrich spatial dynamics, but must be carefully controlled to avoid disrupting the primary light source’s dominant influence. Secondary lights should not create contradictory cast shadows, violate terminator logic, or undermine the spatial hierarchy established by the primary source.

Artists are trained to ensure that secondary illumination supports the scene’s perceptual clarity rather than introducing noise or ambiguity. Typical uses include softening shadow masses (fill light), providing localized reflected illumination (bounce light), or introducing narrative accents without displacing the primary light’s control over major form modeling and edge behaviors.

While secondary light sources are common in real-world environments, their pictorial deployment must remain strategically subordinate, enhancing rather than competing with the primary structure. Effective integration of secondary lighting is critical for advanced chiaroscuro modeling, atmospheric modulation, and compositional depth.”

Self-Occlusion in Form Rendering

“The phenomenon where an object blocks part of itself from view due to its three-dimensional structure, affecting how light interacts with its surface. This occurs when curved, overlapping, or folded areas of a form prevent direct illumination from a light source, resulting in shadow boundaries, value transitions, and contour shifts. The effects of self-occlusion include:

Shadow Formation: Occluded areas receive less direct light, creating cast shadows on adjacent surfaces of the same object. Value Transitions: Smooth or abrupt shifts in light and dark occur based on the curvature and orientation of the form. Contour Complexity: The visible outline of an object may appear broken or interrupted due to parts of the form obscuring others.

Examples can include:  A bent arm, where the forearm casts a shadow onto the upper arm. A curled leaf, where the front-facing portion blocks part of the structure behind it. A rounded apple, where the curved surface causes areas near the edges to fall into shadow.”

Semi-Opaque / Semi-Transparent

“Semi-opaque and semi-transparent are terms describing materials that allow partial transmission of light, occupying a middle ground between full opacity and full transparency. Although often used interchangeably on art materials, the terms carry subtle differences in emphasis important for material control and perceptual outcomes.

Semi-opaque materials tend to block more light than they transmit, offering stronger coverage and partially obscuring underlying layers. They are useful when artists seek to adjust color, build surface density, or modify an image without completely concealing earlier stages.

Semi-transparent materials tend to transmit more light than they block, allowing underlying colors, forms, or textures to remain more visibly integrated with the overlaid material. They are employed to create optical mixtures, glazing effects, and atmospheric transitions that rely on cumulative light passage.

While semi-opacity and semi-transparency primarily describe the quantity of light transmission, translucency differs by affecting the quality of light transmission—scattering light internally and blurring underlying forms. Understanding the continuum between opacity, semi-opacity, transparency, and translucency is critical for managing layering behavior, surface depth, and material realism in both traditional and digital media.”

Semiotics

“The study of signs and sign systems—how meaning is created, communicated, and interpreted through symbols, images, language, or other signifying forms. In visual art, semiotics examines how specific visual elements (shapes, gestures, spatial arrangements, colors, objects) function as signs that carry meaning beyond their perceptual appearance.

The foundational structure of semiotics consists of:

The Signifier – the physical form of the sign (e.g., a drawn skull)
The Signified – the concept or idea that the sign represents (e.g., death)
The Referent – the real-world thing to which the sign ultimately points (e.g., a human skull)

Semiotics is often divided into two branches: Denotation: the direct, literal meaning (what is shown), and Connotation: the associated or implied meanings (what is meant).

Semiotic analysis typically involves three interrelated levels:

Syntactics – the formal relationships between signs (structure, pattern)
Semantics – the relationships between signs and what they signify
Pragmatics – the relationship between signs and their users (context and interpretation)

In the context of representational art, semiotics provides a framework for understanding how and why visual forms carry meaning—particularly when those meanings are culturally assigned, narratively contextualized, or iconographically encoded. A given visual element may act as a denotative sign (direct representation) or a connotative sign (implied or symbolic meaning), depending on its use and the viewer’s interpretive framework.

In A Primer on Pictorial Composition, semiotic awareness is highlighted as a core component of intentional design: the artist must not only construct a visually coherent image, but also recognize how specific forms, orientations, and relationships may suggest, imply, or mislead based on shared perceptual and cultural codes.

Understanding semiotics empowers representational artists to move from description to communication—crafting images that are not just seen, but read, decoded, and engaged with by viewers at multiple levels of interpretation.”

Seven Types of Drapery Folds

“A traditional system used in classical art instruction to analyze how cloth behaves across a range of physical interactions. Originating in close study of Greco-Roman sculpture and Renaissance painting, the classification provides artists with a framework for representing the underlying structure of fabric under the influence of gravity, tension, and body form. Each type reflects a recurring motif in how cloth bends, stretches, or collapses. The types are:

Pipe Fold – Regular, tube-like vertical folds formed by fabric falling from two or more adjacent suspension points. Often seen in heavy drapery or garments.

Drop Fold – Created when fabric hangs from a single support point and falls naturally in a radial or conical shape.

Diaper Fold – A symmetrical pattern of folds produced when fabric is suspended from two distant points, often creating mirrored wave-like shapes.

Zigzag Fold – Angular, accordion-like folds that result from compression, commonly found at joints like elbows or knees.

Spiral Fold – Twisting, helical folds formed when fabric wraps around cylindrical forms such as limbs.

Half-Lock Fold / Tension Fold – A transitional type in which fabric is caught at a tension point (such as a belt or limb) and falls away with directional pull. The ‘half-lock’ version refers to fabric being pinched or trapped, while ‘tension fold’ emphasizes the taut stretching between two points. Inert Fold – Passive folds formed when fabric lies at rest, often pooled on the ground or draped without tension over a surface.

The ‘seven-folds’ concept likely emerged from academic art training in the 18th–19th century, drawing upon careful observation of Greco-Roman sculpture and Renaissance painting. While the system is widely used in figure drawing pedagogy, no original author or dated source is consistently credited with its invention. It is absent from canonical treatises such as Cennino Cennini’s Il Libro dell’Arte or Leon Battista Alberti’s On Painting.

This typology serves as a structural observation guide to help artists render drapery with clarity and believability, reinforcing the logic of movement, compression, and suspension in cloth behavior.”

Sfumato

“(From the Italian sfumare, meaning ‘to evaporate’ or ‘to fade out’) is a painting technique characterized by the soft, gradual blending of tones and colors, creating seamless transitions between light and shadow. This approach eliminates harsh outlines, producing a smoky, atmospheric effect that enhances depth, realism, and the illusion of three-dimensionality. The term was first formally described by Giorgio Vasari in the 16th century, particularly in reference to Leonardo da Vinci’s masterful handling of light and shadow. Leonardo perfected and popularized the technique in works such as Mona Lisa and Virgin of the Rocks, where imperceptible tonal shifts contribute to lifelike rendering.

The execution of sfumato relies on delicate layering and glazing, where thin, semi-transparent paint is applied gradually to soften edges and unify forms. Artists often used soft brushes, feathering, or even dry sponges to diffuse transitions, mimicking how light naturally scatters in the atmosphere. This technique was crucial for simulating aerial perspective, as distant objects appear hazier and less defined due to the diffusion of light. While Leonardo remains the most famous practitioner of sfumato, it was widely embraced by other High Renaissance painters, including Raphael and Correggio, and later refined by Baroque artists such as Rembrandt, who combined it with dramatic chiaroscuro effects. Distinct from other Renaissance techniques, sfumato is often compared to chiaroscuro, which emphasizes strong contrasts between light and dark, and tenebrism, which uses extreme shadows with isolated highlights. Unlike these bolder approaches, sfumato creates a more subtle, ethereal quality, making it particularly effective in portraiture and figurative painting. Its influence extended beyond the Renaissance, inspiring later artistic movements that sought to achieve atmospheric realism through controlled tonal transitions and edge manipulation. The technique remains a fundamental concept in traditional oil painting and contemporary realism, demonstrating the enduring power of soft, imperceptible blending to appeal to the complexity of human perception.”

Sgraffito

“A technique involving the scratching or incising of a top surface layer to reveal a different color, material, or texture underneath, creating contrasting visual effects. The term derives from the Italian sgraffiare, meaning ‘to scratch.‘

Historically, sgraffito has been used extensively in wall painting, ceramic decoration, and architectural ornamentation. The technique became particularly prominent during the Italian Renaissance, where artists and artisans would apply layers of tinted plaster or stucco and then scratch through the upper layers to expose contrasting colors beneath, often producing intricate decorative patterns or figural scenes. Earlier precedents for sgraffito techniques can be found in Roman wall painting and Islamic ceramic traditions.

In contemporary visual art practices, sgraffito is often applied to oil paintings, acrylics, or encaustic works, where a contrasting ground is intentionally covered with a different surface layer and selectively removed using tools such as knives, sticks, or brushes. It can be employed for textural effects, value modulation, fine line work, or surface variation, offering dynamic contrasts and tactile interest within a composition.

Proper execution of sgraffito requires careful control of material behavior, surface preparation, and timing, as different media respond differently to incising depending on their drying stages and film flexibility.”

Shade

“A color mixed with black.”

Shadow

“An area where light from a source is obstructed by an intervening object, resulting in a region of reduced illumination. Shadows are fundamental to the perception and depiction of three-dimensional form, spatial depth, and environmental light behavior within both real-world and pictorial contexts. In visual art and perceptual training, shadows are typically classified into two primary types:

Form Shadow: The gradual, continuous transition on the surface of an object where the surface turns away from the light source, resulting in a decrease in illumination. Form shadows are essential for conveying volume and curvature and are defined by local surface behavior relative to the primary light source. (In the Waichulis Curriculum, Form Shadows are often referred to as ‘Attached Shadows.‘)

Cast Shadow: The distinct shadow that an object projects onto another surface when it blocks the path of light. Cast shadows typically exhibit sharper edges near the occluding object and softer edges farther away, influenced by light source size, distance, and environmental conditions.

Accurate shadow depiction requires careful attention to terminator placement (the boundary between light and shadow on curved forms), value organization, edge quality, and light source logic. In the Waichulis Curriculum, understanding and controlling shadow behavior is essential for maintaining spatial consistency, structural believability, and perceptual clarity in both drawing and painting.

Shadows also interact with secondary light sources, bounce light, and ambient light, introducing subtle variations within shadow masses that must be managed to maintain coherence with the primary lighting structure.”

Shape Replication

“A core perceptual-motor exercise in the Waichulis Curriculum designed to train the learner to reproduce two-dimensional figures with increasing accuracy and efficiency. The exercise presents a visual shape (typically a configuration of lines within a boundary box) that the student must replicate adjacent to the original, using measurement strategies such as visual estimation, sight-size, and comparative methods. The goal is to cultivate precise spatial observation, error correction through feedback, and progressively refined control of material application.

While shape replication is often associated with ‘learning to see’, it is important to clarify that drawing or painting skills do not enhance vision in the sense of granting access to more veridical or bottom-up perceptual data. As supported by research such as Patrick Cavanagh’s work on visual expertise, trained artists do not exhibit privileged access to early-stage visual processing. The visual system remains fundamentally non-veridical—constructing perceptions based on probabilistic inferences, context-driven heuristics, and empirical experience rather than one-to-one mappings of the external world.

Instead, the power of shape replication lies in its ability to foster a learned mapping between perceived structures and procedural motor responses. Through repeated practice, the learner begins to associate specific visual angles, proportions, or curvatures with internalized motor sequences that can reliably reproduce the observed configurations. In other words, shape replication helps ‘marry’ observed elements to practiced motor programs: when I perceive this angle, I know that this series of mark-making movements will yield a figure that elicits a matching perceptual experience. This perceptual-action coupling is a cornerstone of the curriculum’s emphasis on calibration, not correction—training the student to generate consistent results despite the inherent ambiguity and distortions of the visual system.

Beyond mark accuracy, shape replication also strengthens attentional focus, spatial chunking, directional stroke control, and error analysis. It provides a highly adaptable framework for repeated exposure to perceptual problems that will recur in later exercises—particularly those involving form construction and spatial development.

In this way, shape replication is not simply a copying exercise; it is a perceptual-motor calibration platform that builds the procedural fluency necessary to translate ambiguous perceptual input into precise, intentional visual output.”

Sheen

“The measured degree of light reflection from a surface, describing where a material falls on the continuum between full glossiness and complete matte diffusion. It represents the surface’s ability to reflect light in a specular (mirror-like) direction versus scattering it diffusely across multiple angles.

Glossy finishes reflect most light directionally, producing sharp highlights and strong surface definition, while matte finishes scatter incoming light widely, minimizing surface reflections and creating a soft, diffuse appearance. The gloss level of a surface—including paints, coatings, or other materials—can also affect the apparent color, saturation, and texture perception under different lighting conditions.

Between fully matte and fully glossy extremes, a range of intermediate sheen levels is commonly recognized, although terminology is not universally standardized. These include:

Matte: Exhibits minimal specular reflection; surface appears soft and diffuse

Eggshell: Displays very low sheen; slight soft reflection visible at certain angles.

Satin: Shows moderate sheen; soft, broad highlights appear under direct lighting without mirror-like sharpness.

Silk: Similar to satin but typically slightly smoother or more refined in appearance, depending on the manufacturer.

Semi-gloss: Produces clear, noticeable reflections; highlights are more defined, but surface texture may still be somewhat visible.

High-gloss: Reflects light strongly and directionally; surface appears mirror-like with sharp, distinct highlights.

In visual arts, controlling surface sheen is critical for managing perceived value structure, surface behavior, and material realism. Inconsistent or unintended variations in sheen can disrupt spatial coherence, edge readability, and compositional balance within a representational work. Understanding sheen behavior allows artists to better predict and manipulate how surfaces interact with environmental lighting.”

Siccative

“A substance that accelerates the drying process of oil-based paints and mediums by catalyzing (accelerating a chemical reaction without being consumed in the process) the oxidation and polymerization of the binder (typically drying oils such as linseed, walnut, or safflower oil). Siccatives function as drying agents, increasing the rate at which the oil film reacts with atmospheric oxygen to form a solid, crosslinked network.

Traditional siccatives often consist of metallic salts—such as compounds of cobalt, manganese, or lead—that act as catalysts without being consumed in the chemical reaction. By promoting faster surface and bulk drying, siccatives allow artists to reduce handling times, layer paintings more efficiently, and manipulate material behavior for specific technical effects.

However, excessive or improper use of siccatives can compromise the structural integrity of the paint film, leading to issues such as embrittlement, cracking, surface wrinkling, or uneven curing. Best practices recommend cautious, minimal use of siccatives, carefully balancing drying acceleration against long-term material stability.

In modern painting practice, commercially available siccative mediums (often labeled as ‘driers’) provide standardized formulations to help regulate drying times without introducing the risks associated with uncontrolled metallic salt addition.”

Sight-Size

“A drawing and painting methodology that enables the artist to achieve precise proportional accuracy by arranging the subject and artwork so that both appear at a one-to-one scale when viewed from a fixed vantage point. This system requires the artist to step back to a predetermined viewing distance, typically 5 to 10 feet from the easel, ensuring that direct optical comparisons can be made between the source subject and the destination surface​. Alignment between the subject and the artwork is critical, as the distance between them determines the size at which the subject is rendered. Common tools used in the Sight-Size method include a plumb bob, string, or a measuring stick to verify proportions and maintain alignment. This method is widely used in classical atelier training (influenced by the French Academic system) and is particularly well-suited for still life, portraiture, and academic realism, where a high degree of accuracy is required. However, it is less adaptable for dynamic compositions or large-scale works, as it relies on a single, fixed viewing position. Because it emphasizes direct observation over interpretive proportional judgment, Sight-Size can be an excellent tool for training the eye but may limit an artist’s ability to work from varied perspectives​.”

Signifier (Affordances)

“In the context of affordances, a signifier refers to any perceivable cue that indicates or highlights the existence of a potential action possibility (affordance) offered by an object or environment. While affordances themselves are relational properties between the observer and the object (i.e., what the object affords based on the perceiver’s capabilities), signifiers are features that signal these affordances to the observer, improving the likelihood that they are perceived correctly and acted upon.

For example, a flat, sturdy surface may afford sitting, but without appropriate visual, tactile, or contextual signifiers (like a familiar chair shape, or a visible seat edge), the sitting affordance might be missed or misinterpreted. In design and visual composition, deliberate use of signifiers can clarify affordances by making actionable possibilities more obvious, reducing perceptual error or hesitation.

This conceptual pairing—affordance and signifier—is essential because while affordances can exist independent of perception (a stone affords throwing regardless of whether a person sees it that way), the presence of effective signifiers increases the perceptual salience of affordances, facilitating faster, more accurate interactions​.”

Silhouette

“A two-dimensional representation of the outermost boundary of a form, depicted as a solid, usually featureless shape—typically rendered in a single, uniform value (often black) against a contrasting background. A silhouette captures the essential profile or contour of an object without conveying internal details, texture, or surface variations. Its utility lies in maximizing figure/ground contrast, emphasizing the spatial separation of forms based solely on outer boundaries​.

The term ‘silhouette’ originates from Étienne de Silhouette (1709–1767), a French finance minister whose name became associated with inexpensive shadow-portraiture in mid-18th-century France. As such, portraits required only the simple tracing and filling of a person’s profile, they came to be humorously referred to as being ‘à la Silhouette’—a metaphor for something cheap or minimalistic. In practice, silhouettes differ from contours and cameos:

A contour refers to the perceived or depicted boundary that defines the edge of a form and may adapt dynamically to surface undulations or volumetric changes, suggesting depth and three-dimensionality​.

A cameo, particularly in historical contexts, refers to a method of low-relief carving or depiction where a figure is raised against a background, often employing color or material differences. In visual composition, cameo lighting or cameo composition may describe a luminous subject emerging from a dark background, but it still maintains some internal information, unlike a pure silhouette.

Thus, while silhouettes isolate shape through maximal contrast without internal detail, contours communicate surface form and structure, and cameos blend low-relief modeling or selective illumination to emphasize foreground elements.”

Silver Leaf

“A thin, delicate sheet of silver, traditionally produced by mechanical hammering or rolling, used in gilding processes to impart a brilliant, reflective surface. Unlike gold leaf, silver leaf cannot be beaten to quite the same extreme thinness, resulting in a slightly heavier and more manageable material. Sheets are typically sold in small square formats (approximately 3⅜” to 5″ squares), and like gold, may be packaged between tissue papers in books of 25 leaves​.

Silver leaf is applied using similar techniques as gold leaf, primarily through water gilding (over a prepared gesso and bole surface) or oil (mordant) gilding (on sealed, non-absorbent surfaces with adhesive size). However, silver’s reactivity distinguishes it from gold: it readily tarnishes when exposed to air and humidity, forming a layer of silver sulfide. Therefore, artworks incorporating silver leaf generally require careful post-application sealing with lacquers, shellacs, or varnishes to preserve the intended reflective appearance​.

Historically, silver leaf was sometimes intentionally coated with transparent golden lacquers to imitate the appearance of gold when true gold leaf was either cost-prohibitive or unavailable. However, due to its vulnerability to tarnishing, palladium leaf—a non-tarnishing member of the platinum group—has become a popular modern substitute for silver leaf in conservation and fine art applications​.

Silver leaf interacts with light differently from gold. While gold reflects a warm, yellow tone regardless of environment, silver leaf reflects the ambient light color much more strongly. This high reflectivity and chromatic neutrality mean silver leaf can appear brilliant white, steely blue, or even dark gray depending on surrounding conditions. Additionally, when employed compositionally, silver fields often function more as light sources than traditional pigment-based surfaces, behaving similarly to mirrors under direct illumination.

Due to its chemical properties, silver leaf presents unique challenges:

Tarnishing Risk: Without a proper barrier layer (lacquer or polymer sealer), silver will oxidize over time.

Thickness Variability: Silver leaf is thicker and thus easier to handle than gold leaf, but does not offer the same degree of burnishability for ultra-mirror finishes.

Storage Considerations: Silver leaf must be kept in dry, airtight environments to prevent premature discoloration​.

The tradition of using silver in gilding dates back to antiquity, paralleling the use of gold in decorative arts, religious icons, and manuscript illumination. However, due to silver’s tendency to tarnish, it has historically seen less usage in contexts requiring long-term visual consistency unless paired with protective coatings.”

Simultaneous Brightness Contrast

“A spatial context effect in which the perceived brightness (or lightness) of an area is altered by the luminance of surrounding regions. A gray area appears darker when placed against a lighter background and lighter when placed against a darker background, even though its actual luminance remains unchanged. This effect is not solely due to lateral inhibition but also involves higher-level perceptual processes related to contrast enhancement and contextual interpretation​.”

Simultaneous Color Contrast

“A phenomenon in which the perceived color of an area is influenced by the color of its surrounding context. If the target area is neutral gray, it will take on the opponent color of the surrounding field (e.g., appearing greenish when surrounded by red). If the target itself is chromatic, its hue will be altered toward the opponent of the background color to a degree dependent on its saturation and exposure duration.

The first systematic investigation of this phenomenon is widely attributed to Michel Eugène Chevreul, a 19th-century French chemist. While working as the director of dyes at the Gobelins Manufactory in Paris, Chevreul was confronted by complaints that dyed black yarns were inconsistent in color. After investigation, he found the issue was not with the dyes themselves but with the way the perceived color of one yarn was influenced by the color of adjacent yarns. This perceptual interaction—what he termed simultaneous contrast—became a foundational concept in both color theory and visual perception.

Chevreul’s documentation of these interactions was later published in The Principles of Harmony and Contrast of Colors (1839), which profoundly influenced artists like Delacroix, the Impressionists, and the Neo-Impressionists (including Seurat). His observations helped bridge the gap between scientific color interaction and pictorial application, laying groundwork for empirical approaches to color composition in visual art.

Simultaneous color contrast is now understood to arise from opponent-process mechanisms and context-dependent neural coding, where visual system cells sensitive to chromatic differences amplify distinctions between adjacent hues. This serves adaptive functions by enhancing edge detection and object segregation within complex visual environments.”

Simplification Rule (Logic)

“A valid rule of inference (a logical principle that defines how new truths can be derived from established premises within a formal system. Rules of inference preserve truth and structure the progression of deductive arguments) in formal systems such as propositional logic, predicate logic, and specifically natural deduction frameworks. It states that from a conjunction (A ∧ B) (read as ‘A and B’), one can infer either conjunct individually. That is, if the statement ‘A and B’ is known to be true, it logically follows that both ‘A’ and ‘B’ are each true independently. This is formally expressed as:

From: (A ∧ B) – Infer: A – Infer: B

This rule preserves truth and is one of the elementary valid inference patterns for deductive reasoning, supporting the decomposition of complex expressions into simpler, verifiable components. For example:

Given: ‘It is raining and it is cold.’ Using simplification: → ‘It is raining.’ → ‘It is cold.’

In formal proof construction, simplification allows a proof-writer to extract usable premises from compound statements. It is essential for moving from complex premises to actionable steps in deductive reasoning.”

Simulacrum

“(Plural: simulacra) A representation or imitation of a person, object, or experience that does not necessarily maintain a direct or faithful correspondence to the original it references. Instead, a simulacrum often becomes a substitution, an autonomous entity that may evolve independently of any original referent. In visual, philosophical, and perceptual contexts, a simulacrum can capture the appearance of something without necessarily replicating its full reality or internal structure​.

The term derives from Latin simulacrum, meaning ‘likeness, image, or effigy,’ itself stemming from simulare (‘to make like, to imitate’)—which is also the root of simulate. Early uses referred to statues, paintings, or effigies. Over time, particularly through philosophical traditions (notably Plato and later Jean Baudrillard), simulacrum gained a critical sense: a copy with no original, or a hollow imitation.

Key Distinctions from simulation, replica, and surrogate include:

Simulacrum vs Simulation: A simulation refers to an active process or system that attempts to replicate behaviors, appearances, or outcomes of a real-world system. A simulacrum is the resulting static or perceptual artifact that might imitate appearance without functional or causal similarity.

Simulation = process/activity – Simulacrum = product/image/percept

Simulacrum vs Replica: A replica is generally intended to be a faithful reproduction of an original, striving for accuracy in material, form, and function. In contrast, a simulacrum may capture surface resemblance but can diverge dramatically from the original’s meaning, function, or context.

Simulacrum vs Replica: A surrogate refers to a substitute that intentionally stands in for another entity, often striving to replicate essential functions or experiences. In contrast, a simulacrum may superficially resemble an original without necessarily preserving its function, context, or full experiential equivalence. While surrogates aim to functionally ‘stand in,’ simulacra may only ‘look like.’

In representational art and perceptual surrogacy, the term simulacrum is critical because an artist is not creating an objective duplicate of reality, but a perceptual construct that evokes the experience of the original. As noted in Waichulis’ What Does Realistic Look Like, a realistic work strives not for veridical duplication but for a perceptual simulacrum that elicits similar experiential responses​.”

Sizing / Size (Painting)

“A thin, penetrating solution (a preparation that absorbs into the fibers or surface matrix of a material without forming a separate, continuous external layer. It stabilizes and modifies internal properties—such as porosity or absorbency—rather than creating an independent film or skin)—commonly made from animal glue, gelatin, casein, or diluted shellac—used to seal and prepare a porous support surface (such as canvas, paper, or gesso) prior to the application of grounds or paints. The primary function of sizing is to fill the pores of the support material, isolate it from subsequent layers, regulate absorbency, and protect it from chemical interactions that could cause deterioration​.

In painting, the size is not intended to form a continuous, smooth film (like a varnish or ground) but rather to subtly infiltrate and stabilize the support. For canvas painting, sizing is a crucial barrier preventing direct contact between the reactive oil in paint films and the cellulose fibers of the cloth, thereby delaying or mitigating the rotting of the support over time​. Materials commonly used for sizing include:

Rabbit-skin glue: Traditionally favored due to its balance of adhesive strength, flexibility, and moisture response.

Gelatin: A purified form of animal protein, also widely used, especially in papers.

Casein: Occasionally used where a harder, more water-resistant layer is desirable, although it is generally more brittle than glue.

Diluted shellac or formaldehyde-treated solutions: Sometimes employed for specialized grounds where moisture resistance is critical​.

Important distinctions include: A size is a penetrating treatment, not a ‘coating’ that forms a separate film. Mayer emphasizes that a properly made size should only reduce absorbency without entirely blocking it​. Excessively heavy or film-forming sizing (thick glue or casein layers) can be detrimental, leading to mechanical instability and scaling under oil grounds​. Sizing also serves as a fixative layer when drawings are made on gesso before painting​.

The practice of sizing dates back to ancient panel paintings and became standardized in Medieval and Renaissance panel and canvas preparation. Its correct application was critical in ensuring the longevity of major works and is still vital for conservation-grade painting practices today.

In the Waichulis Curriculum, rigid supports such as hardboard (Masonite) panels are primed directly with multiple layers of acrylic gesso. As such, a separate sizing agent is not required. The acrylic gesso serves both as a sealant—penetrating and stabilizing the substrate—and as a ground, providing a suitable surface for subsequent painting applications. This approach simplifies preparation while ensuring durability, dimensional stability, and appropriate surface absorbency for the highly controlled mark-making that the curriculum emphasizes.”

Sketch / Sketching

“A rapidly executed image that captures the essential structure, mass relationships, or concept of a subject without focusing on refined detail or finish. Sketching refers to the act of creating such an image, often serving as an early step in the planning, analysis, or problem-solving stages of a work. Although sketching is commonly associated with drawing, it is not limited to dry media; it can be carried out with ink, paint, or digital tools—any medium that allows for quick, responsive mark-making​.

The term derives from the late 17th-century Dutch schets, which traces back to the Italian schizzo (‘a rapid drawing’ or ‘splash’), and ultimately to the Latin schedium, meaning ‘an improvised composition’. This lineage reflects the fundamental character of a sketch: immediacy, adaptability, and the establishment of primary relationships rather than polished completion.

Historically, sketching has served both preparatory and independent purposes. During the Renaissance, artists such as Leonardo da Vinci and Michelangelo used sketches to work through compositional and anatomical problems, often treating them as valuable records of the creative process. In academic traditions of the 18th and 19th centuries, sketching was a core component of training, used to develop structural understanding, proportional relationships, and rapid observational skills​.

A sketch typically focuses on establishing the basic forms, directional flow, and major spatial relationships of a subject. It does not pursue meticulous refinement or surface resolution. In contrast to a study, which may concentrate intensively on a particular aspect, such as lighting, anatomy, or texture, with greater deliberation and finish, and in contrast to a drawing, which often denotes a more fully developed and complete image, a sketch remains provisional and open to revision. However, some sketches possess an immediacy and coherence that allow them to stand as independent works.

Within the Waichulis Curriculum, sketching is employed to develop perceptual acuity, spatial reasoning, structural organization, and material control. Sketches are treated as crucial exercises that lay the groundwork for deliberate, representational efforts requiring more rigorous control and resolution.”

Skill

“An organized, learned ability to carry out a task with determined results, often with minimal expenditure of time, energy, or conscious attention. It reflects the successful integration of perceptual, cognitive, and motor processes into fluid and coordinated performance. Skills can be domain-specific or general, and they may involve both physical and mental components, depending on the nature of the activity​. The word derives from the Old Norse skil, meaning ‘discernment’ or ‘knowledge.’ Over time, it came to refer not just to the understanding of a task, but the proficient execution of it.

The acquisition of skill typically follows a progression from initial, effortful cognitive control (conscious monitoring and decision-making) to more autonomous, streamlined performance with practice​. As proficiency develops, action sequences are chunked into larger, more manageable units, reducing cognitive load and allowing smoother, faster, and more accurate execution.

Foundational models such as the Fitts and Posner three-stage model (cognitive, associative, and autonomous stages) describe how skill acquisition transforms performance from deliberate and conscious to automatic and efficient​. Research across domains—from perceptual-motor activities (sports, surgery) to intellectual pursuits (chess, mathematics)—shows that deliberate practice and the development of domain-specific mental representations are critical to high-level skill development​.

Distinctions include:

Skill vs. Knowledge: Knowledge refers to stored information or understanding about a subject; skill refers to the ability to perform an action effectively.

Skill vs. Talent: Talent is often viewed as innate potential, while skill is acquired through experience, training, and deliberate practice.

Skill vs. Habit: While skilled actions may become automatic, skill is distinguished from mere habit by its adaptability and goal-directed nature.

Within the Waichulis Curriculum, skill development is treated as the deliberate, structured refinement of perceptual, cognitive, and procedural capacities. Exercises are designed to progressively build operational fluency, control, and adaptability, ensuring that complex tasks can eventually be executed with precision, minimal cognitive strain, and creative flexibility.”

Skill Ladder Metaphor

“A conceptual framework used to describe the ongoing nature of skill development and mastery. In this metaphor, the journey toward mastery is imagined as a climb up an infinitely tall ladder, with each rung representing a discrete, incremental gain in skill. Although early stages of ascent produce visible, dramatic changes from an external perspective, continued progress eventually becomes imperceptible to outside observers—despite remaining highly dynamic, challenging, and meaningful to the practitioner.

At the base of the ladder, each rung is easily discernible, and each step of progress is both rapid and externally visible. As the climber ascends, however, the distance from the ground increases, and to distant observers, the climber appears to move less and less, eventually seeming almost stationary. Nevertheless, for the climber, the experience of ascent remains consistent; each rung is spaced identically, each effort yields real advancement, and the view of higher goals remains ever-expanding beyond the visible horizon.

The Skill Ladder Metaphor highlights a critical reality in deliberate practice and mastery development: perceptible progress is relative to the vantage point of the observer. What may seem narrow, static, or repetitive to onlookers may, in fact, be an immersive, ongoing engagement with an increasingly expansive and complex experiential landscape.

Historically echoed in the reflections of virtuoso practitioners—such as cellist Pablo Casals, who continued to practice intensively into his eighties because he still perceived growth. When asked why he continued to practice four and five hours a day, Casals answered simply, ‘Because I think I am making progress.‘ The Skill Ladder Metaphor emphasizes that true expertise is not defined by external appearances of novelty or diversification, but by the internal experience of continual refinement, discovery, and forward movement.

The Skill Ladder Metaphor serves to contextualize the structure of deliberate practice. Students are encouraged to recognize that meaningful skill development may not always produce immediate or externally visible signs of change, but steady, mindful ascent remains critical to long-term growth and creative fulfillment.”

Smartermarx

“An educational forum and digital resource repository dedicated to the advancement of skill-based visual art, critical inquiry, and empirical discourse. Founded by Anthony Waichulis and currently curated by artist and designer Ava Ash-Waichulis, Smartermarx serves as a platform for the dissemination of research, technical instruction, perceptual science insights, and structured artistic training methodologies.

The forum supports a wide range of discussions focused on representational painting, drawing, visual perception, materials science, and cognitive principles relevant to artistic practices. It emphasizes empirically grounded content over tradition-based dogma and fosters a community environment that prioritizes critical thinking, evidence-based exploration, and productive dialogue.

Smartermarx functions both as an extension of the Waichulis Curriculum philosophy and as an independent archive for articles, instructional guides, research summaries, technical demonstrations, and methodological debates. Through curated discussions and resource-sharing, it aims to equip artists with the tools necessary for deliberate practice, perceptual development, and creative autonomy.

While access to Smartermarx requires membership approval, the platform is intended to be inclusive of learners at various stages of their development, provided they engage with a shared respect for empirical inquiry and constructive critique.”

Smudger

“A general term for a tool used to blur or diffuse marks on a drawing surface, most often in dry media like charcoal or graphite. Common smudging tools include tortillons, stumps, chamois, or even fingers. These tools are used to rub material across the surface, producing a softened or blended effect. However, in the Waichulis Curriculum, smudgers are explicitly avoided in foundational exercises. This is because such tools can compress the paper’s tooth, obscure directional stroke information, and reduce the artist’s capacity to control transitions through deliberate material placement and pressure. Instead, blending is taught as a function of precision and control—using stroke tapering, pressure modulation, and layering—without relying on artificial manipulation that can undermine structural intent or observational clarity.”​

SNAG (Survey, Notan, Anchors, and Gradations)

“A structured approach within the Waichulis Curriculum that guides the systematic development of representational imagery. The methodology is designed to facilitate color/value organization and application through four sequential stages:

Survey (S) – The initial planning phase, where boundaries, spatial landmarks, and major disparities are identified using centerlines, boundary boxes, contours, outlines, or envelopes.

Notan (N) – The establishment of broad light and dark patterns, capturing low-spatial frequency information with soft material and light pressure to create an initial framework.

Anchors (A) – The placement of key values or colors, reinforcing the darkest darks, lightest lights, or highest-chroma marks to serve as reference points for the subsequent development of form.

Gradations (G) – The refinement of transitions between values and colors, expanding outward from anchors while ensuring smooth, controlled applications that preserve surface quality.

This approach is particularly emphasized in gradation block exercises and is fundamental to the curriculum’s structured methodology for relative accuracy and technical refinement.”

Soap

“A substance made by the chemical reaction (saponification) of fats or oils with an alkali, such as sodium hydroxide (lye) or potassium hydroxide. In aqueous solution, soap molecules organize into structures called micelles, where the hydrophobic (‘water-fearing’) tails cluster inward and the hydrophilic (‘water-loving’) heads face outward toward the water. This micellar structure enables soap to emulsify and lift away oily or greasy contaminants, allowing them to be rinsed off with water​.

Soap molecules surround non-polar (oil or grease) particles with their hydrophobic ends, while their hydrophilic ends remain in contact with the surrounding water. This dual affinity allows insoluble materials to become suspended as emulsions in water, enabling removal from surfaces​.

In the Context of Oil Painting: Soap plays several important but highly cautious roles in the maintenance of oil painting materials:

Brush Cleaning: Proper brush hygiene after painting requires the removal of residual paint, typically by first rinsing in solvent (such as turpentine or mineral spirits) and then washing thoroughly with soap and warm water​​. This prevents pigment buildup, protects brush hair integrity, and extends the usable life of tools. In the Waichulis Curriculum, solvents are NOT used to clean brushes. Rather, painters wipe all excess paint from the brush and simply wash with soap and water (gently) for use the following day.

Conservation and Cleaning: The use of soap solutions for cleaning oil paintings has historically been highly controversial. While pure, neutral soaps have sometimes been cautiously employed on intact, uncracked surfaces, the risks are considerable. Improper soap application can lead to water infiltration into cracks, drawing pigment particles into solution, or damaging delicate varnish and paint films​. Modern conservation generally discourages amateur use of soaps on paintings, reserving such interventions for highly experienced professionals only.

Saponification Risks: In oil paintings, the binding medium—usually a drying oil like linseed oil—undergoes chemical changes as it cures, forming a flexible but delicate polymer network. If soap residues containing free alkali (strong basic substances like sodium hydroxide or potassium hydroxide) come into contact with the paint surface, they can chemically react with the oil components. This reaction, called saponification, breaks down the oil into soap and glycerol. In a painting, unintended saponification can lead to:

Color alteration: Disruption of the oil matrix can change the refractive index of the paint layer, affecting color saturation, brightness, or tone.

Weakening of the paint film: The breakdown of binding oils compromises the mechanical integrity of the paint, making it more brittle, crumbly, or prone to cracking.

Increased environmental vulnerability: A weakened surface is more susceptible to moisture infiltration, dirt accumulation, or physical abrasion.

Thus, even seemingly benign soap use can pose serious risks if residual alkalis remain on a painting or penetrate a vulnerable paint film​.

Additional Notes: A carefully made neutral soap (such as shaving soap or castile) produces minimal free alkali upon dissolution, reducing potential risks compared to harsher detergents. Specialized soaps like saponin (from soap-tree bark) have been recommended in some historical contexts as safer alternatives for very delicate surfaces​.”

Social Realism

“An art movement and ideological stance that emerged primarily in the early 20th century, focused on the representation of working-class life, labor conditions, and socio-political struggle. Influenced by 19th-century Realism, Marxist theory, and post-revolutionary aesthetics, Social Realism sought to expose inequality, critique systems of power, and promote collective consciousness through accessible, narrative imagery.

Artists such as Diego Rivera, Ben Shahn, Dorothea Lange, and Jacob Lawrence used a variety of media to document and dramatize the lived conditions of marginalized groups. While stylistically varied, social realist art maintains a commitment to ideological clarity, visual legibility, and empathetic portrayal. It is realism not only of appearance but of purpose—intended to mobilize public awareness and social change.”

Solvent

“A liquid capable of dissolving other substances without undergoing chemical change itself. In painting practice, solvents are used to dissolve oils, resins, varnishes, and pigments, facilitating adjustments in viscosity, handling, and material preparation​. Solvents act at the molecular level, surrounding solute particles and separating them into a true solution. Dissolution differs from mere physical dispersion because it involves molecular-level interaction without altering the fundamental chemical structures of either the solvent or the solute​.

In the Context of Painting, solvents are often used for: Thinning Paints and Mediums: Adjusting consistency for specific techniques such as underpainting, glazing, or stumbling. Dissolving Resins: Preparing varnishes or mediums (e.g., dissolving damar resin into turpentine). Cleaning: Removing oil-based residues from brushes, palettes, and tools. Conservation Work: Carefully dissolving aged varnishes or grime layers during restoration without damaging underlying paint​.

Common solvents in artistic use include turpentine, mineral spirits, acetone, alcohol, and essential oils such as spike oil. Each differs in volatility, solvent strength, toxicity, and evaporation behavior.

Important Distinction — Solvent vs. Diluent: While a solvent is defined by its ability to dissolve a substance, a diluent is defined by its function: to reduce viscosity by physically dispersing components without necessarily causing dissolution. The same liquid (such as turpentine) may act as a solvent in one context (e.g., dissolving damar resin) and as a diluent in another (e.g., thinning oil paint). In short: dissolving involves creating a solution through molecular interaction, diluting involves reducing viscosity through dispersion without chemical change. The distinction lies not in the substance itself, but in its application​.

An effective solvent should: evaporate completely without leaving residues, exhibit consistent evaporation behavior aligned with the working method, avoid damaging cured or uncured paint films, and be chemically stable in relation to binders and pigments.

It is very important to note that solvents are typically volatile and flammable, requiring careful handling in ventilated environments. Long-term inhalation or skin exposure to certain solvents (e.g., benzene-containing turpentine substitutes) presents serious health risks​.

The widespread use of volatile organic solvents in painting began with advances in distillation during the Renaissance, enabling new techniques in glazing and varnishing that were not possible in purely tempera-based traditions. Within the Waichulis Curriculum, the use of traditional volatile solvents, such as turpentine or mineral spirits, is not employed at any stage of the painting process. Students are trained to manage materials without the assistance of such agents, ensuring the development of disciplined application habits, the preservation of paint film strength, and the maintenance of a safe, non-toxic studio environment. Cleaning of tools and materials is conducted using non-solvent-based methods, such as mechanical removal of paint residue and washing with soap and water. This approach aligns with best practices in material longevity, health safety, and responsible studio management​.”

Space (Visual)

“In visual art and perceptual science, space refers to the organization of visual elements to create the illusion or perception of depth, dimensionality, and spatial relationships within a two-dimensional surface or three-dimensional environment. Visual space concerns how forms occupy, relate to, and define spatial intervals relative to each other and to the observer.

Space in visual contexts can be actual—as in three-dimensional installations or sculptures—or ‘illusionistic‘, as in two-dimensional paintings and drawings where depth and volume must be inferred from visual cues. The perception of space depends on the integration of multiple mechanisms, including overlap, size diminution, atmospheric perspective, linear perspective, edge clarity, tonal contrast, and color temperature relationships​.

Historically, the formal depiction of visual space evolved significantly during the Renaissance with the codification of linear perspective, allowing artists to systematically create convincing illusions of depth on flat surfaces. Earlier traditions, such as medieval art, often treated space symbolically or hierarchically rather than perceptually. Key distinctions within visual space include:

Positive space: Areas occupied by primary subjects or forms.

Negative space: Areas surrounding and between subjects, crucial for defining form relationships.

Pictorial space: The perceived ‘window’ into a spatial environment created on a two-dimensional surface.

Physical space: The actual three-dimensional environment in which objects exist.

In representational art, controlling the perception of space is fundamental to conveying realism, volumetric form, spatial relationships, and viewer immersion. Spatial cues must be strategically managed to produce coherent and convincing visual experiences.

In the Waichulis Curriculum, the strategic development of visual space is emphasized through exercises in mass relationships, value gradations, edge hierarchies, and compositional structuring. Students are trained to control spatial perception deliberately rather than relying on mechanical or formulaic perspective systems alone, fostering a deeper understanding of spatial mediation through value, edge, and form dynamics.”

Spatial Biases in Composition

“The tendency for visual elements to be interpreted differently based on their position within a frame, influenced by perceptual and cultural expectations. For example, in many cultures, left-to-right reading habits create a bias where elements placed on the right side of an image may feel like a conclusion or destination, while those on the left suggest an introduction or origin. Other common spatial biases include top-heaviness (where higher elements seem dominant or uplifting) and center bias (where central placement attracts the most attention). Understanding spatial biases allows artists to intentionally promote or encourage a certain visual flow and reinforce narrative meaning in compositions.”

Spatial Chunking

“The perceptual strategy of grouping multiple visual elements or spatial relationships into manageable units for more efficient observation, memory, and reproduction. In the context of the Waichulis Curriculum, spatial chunking supports the learner’s ability to navigate complex visual arrangements—such as proportions, alignments, negative space, or compositional structures—without becoming overwhelmed by discrete, isolated details.

Rather than processing each visual element (e.g., every line, angle, or distance) as an independent measurement, spatial chunking allows the artist to perceive and encode higher-order groupings—such as relative spacing between forms, angular clusters, or overall envelope shapes. These groupings can then be compared, stored, and replicated more efficiently during tasks such as Shape Replication, Gradation Patterns, or Form Box construction.

The process is an extension of perceptual chunking, a well-documented cognitive phenomenon in which repeated exposure to patterned information enables the brain to consolidate multiple bits into single mental units or schemas. In visual art, spatial chunking increases attentional efficiency and supports more global, holistic processing—allowing the learner to move from detail fixation toward structure-driven observation.

Like other chunking strategies, spatial chunking is built gradually through exposure, repetition, and feedback. Early exercises like the Origin-Destination Line introduce the concept in a basic linear format, while more complex activities, such as interleaved replication or multi-form construction, demand the development of more sophisticated spatial chunking abilities.”

Spectrum

“A continuous range of values or elements organized according to a particular property, such as wavelength, frequency, energy, or another measurable dimension. It represents a gradation without distinct separations between one part and another, forming a smooth continuum​.

In physics, a spectrum most commonly refers to the distribution of electromagnetic energy across different wavelengths. The visible spectrum, for example, is the narrow range of electromagnetic wavelengths (~400–700 nanometers) that the human visual system can detect. This range includes what is colloquially recognized as the colors of the rainbow: red, orange, yellow, green, blue, indigo, and violet.

In everyday language, the term ‘spectrum’ is often used synonymously with the range of visible colors seen in phenomena such as rainbows, prisms, or spectroscopic displays. However, this common usage only captures a small portion of the broader scientific meaning. True electromagnetic spectra extend beyond the visible range to include radio waves, microwaves, infrared, ultraviolet, X-rays, and gamma rays. Additional relevant usages include:

Reflectance Spectrum: In color science and perception, the reflectance spectrum describes the proportion of light that a surface reflects at each wavelength. It is a key determinant of an object’s perceived color​.

Emission Spectrum: In physics and optics, an emission spectrum shows the wavelengths of light emitted by an object or substance, often used to identify materials.

Spectral Composition in Art: In painting, understanding spectral behavior can influence pigment choice and color mixing strategies, particularly when attempting to approximate the chromatic intensity and luminance balance found in natural phenomena​.

Broader Metaphorical Use: ‘Spectrum’ has also been generalized to refer to any continuum of characteristics, qualities, or states—such as a ‘spectrum of emotions’ or ‘a political spectrum’.

Within the Waichulis Curriculum, the concept of spectrum is fundamental to understanding how hue, value, and chroma are systematically organized. Students are introduced early to the idea that colors exist not as discrete categories but as points along a continuous perceptual range, requiring careful navigation and calibration during observational rendering, color mixing, and compositional design​.”

Specular Highlights

“Bright, reflective areas on a surface that indicate the intensity, position, and nature of a light source. Specular highlights occur when light reflects directly off a smooth surface, creating sharp, well-defined highlights in highly reflective materials (e.g., polished metal, water) and softer, diffused highlights in semi-gloss or matte surfaces. The appearance of specular highlights is influenced by the surface’s texture, angle relative to the light source, and viewing position, making them a critical element in rendering realistic lighting and material properties.”

Spring Clamp

“A handheld fastening device that uses the mechanical force of an internal spring to apply constant, even pressure between two jaws. Designed for rapid application and release, spring clamps are commonly used to temporarily secure objects together, hold materials in place, or stabilize work during assembly or finishing processes.

A typical spring clamp consists of two pivoting metal or plastic arms joined by a central coiled spring. When compressed, the jaws open; when released, the stored energy of the spring forces the jaws shut, maintaining pressure without the need for external adjustment. Rubber or plastic pads are often affixed to the clamping surfaces to protect delicate materials from damage.

In an art studio context, spring clamps are indispensable for securing drawing boards, panels, or canvases to easels or work surfaces, holding back reference materials, drapery, staging elements during life studies, temporarily anchoring masking materials, backgrounds, or compositional guides, and stabilizing objects during still-life setups or compositional construction.

Spring clamps are valued for their portability, ease of use, and ability to apply consistent pressure without the complexity of threaded mechanisms or manual tightening. Distinctions with note are:

Spring Clamp vs. C-Clamp: A spring clamp relies solely on spring tension for pressure, whereas a C-clamp uses a screw mechanism for variable, mechanically adjusted clamping force.

Spring Clamp vs. Binder Clip: While visually similar in some respects, binder clips are designed primarily for securing stacks of paper and are not engineered for broader material clamping applications requiring variable jaw opening or resilient pressure.

Spring clamps are regularly employed in many working studios to secure drawing panels, reference materials, and work surfaces during various training exercises. Their simple, efficient design supports a flexible and orderly studio environment without introducing significant setup time or distraction from the primary focus of skill development.”

Square

“A closed, two-dimensional quadrilateral characterized by four right angles (90 degrees) and four sides of equal length. It is a special case of a rectangle, distinguished by the condition that not only are opposite sides parallel and equal, but adjacent sides are also equal. In Euclidean geometry, the square occupies a central position as a fundamental unit of symmetry, proportion, and modular division.

In the Waichulis Curriculum, the square serves as one of the primary perceptual training tools introduced during the early stages of the Language of Drawing (LOD) phase. Mastery of the square facilitates the learner’s sensitivity to uniform proportion, axis alignment, planar consistency, and orthogonal relationships critical for building more complex volumetric forms such as cubes, grids, and perspectival scaffolds.

The training emphasis on squares is not limited to passive replication. Instead, squares are used to develop operational control over the perception and construction of regularity, balance, and modular subdivision within a pictorial space. This early foundation supports later compositional challenges involving proportional hierarchies, spatial calibration, and the depiction of structured environments.

While often encountered in static or decorative contexts, the square’s importance within perceptual training lies in its dynamic role as a module of division, a calibrator of space, and a reference for controlling scale transformations across two-dimensional and three-dimensional constructions.”

Stabilizer (Painting)

“In the context of painting materials, a stabilizer refers to an additive incorporated into paint formulations to preserve uniform consistency, prevent pigment settling (pigment settling refers to the gradual descent of heavier pigment particles to the bottom of a container over time, leading to separation from the binder and resulting in inconsistent texture, reduced color uniformity, and difficult reconstitution during use), and inhibit the separation of oil from pigment during storage. Stabilizers are used particularly in oil paints to maintain a workable, buttery texture over time, especially while paints are stored in tubes or containers​.

Stabilizers improve the physical handling properties of paints by: keeping pigment particles evenly suspended within the oil vehicle, preventing syneresis (the separation of oil from the pigment mass), and modifying viscosity to achieve a ‘short’ or ‘buttery’ consistency, rather than a ‘long’ or ‘stringy’ paste, which can otherwise occur naturally with certain pigments​.

The three main classes of materials used as stabilizers in oil paints include:

Waxes or wax-like substances (e.g., beeswax), which create a colloidal or gelatinous condition within the paint.

Water or aqueous solutions, used to form emulsions (although their use is generally discouraged in oil paints due to risks of spongy films and increased yellowing).

Metallic soaps (e.g., aluminum stearate or zinc stearate), which act as thixotropic agents to modify consistency​​.

The term ‘stabilizer’ was originally borrowed from emulsion chemistry and first used in this capacity during the early 20th century. Before the widespread addition of stabilizers, artists preparing their own paints had to manually accommodate variations in pigment behavior—learning to manage the naturally ‘stringy,’ ‘short,’ or ‘stiff’ qualities that different pigments exhibited​.

With the commercial packaging of oil paints in metal tubes during the nineteenth century, the pressure to create paints with uniform, easily brushable consistencies grew, leading manufacturers to introduce stabilizers systematically. This change helped standardize painting experiences for users, but at the potential cost of certain material qualities and, in some cases, the long-term stability of the paint film​.

While small amounts of stabilizers (particularly beeswax) are generally considered harmless, excessive use—especially of metallic soaps like aluminum stearate—can dilute the tinting strength of the paint (by displacing pigment volume), cause sponginess, embrittlement, or premature yellowing of the paint film over time​, and/or mask poor formulation practices in lower-grade paints, leading to deceptive handling qualities but compromised durability.

Within the Waichulis Curriculum, students are encouraged to understand stabilizers not as ‘enhancers’ but as compromises between manufacturing convenience and archival standards. Where possible, learners are taught to recognize natural pigment behaviors and develop material handling skills that do not overly rely on stabilizer-modified products.”

Stack / Stacking / Stack Process

“In the context of historical materials and traditional painting practice, the term ‘stack’ or ‘stacking’ most prominently refers to the ‘stack process’ (also known as the Dutch process)—a historical industrial method used for manufacturing white lead (basic lead carbonate), a key pigment in traditional oil painting. This process, described as early as antiquity by Theophrastus, was extensively used in Europe through the 18th and 19th centuries and is regarded as producing the highest quality white lead pigment, commonly referred to as flake white​.

The Stack (Dutch) Process involved stacking earthenware pots filled with weak acetic acid (vinegar) and suspended strips of metallic lead. These pots were then covered with organic material such as horse manure, tan bark, or spent grain—a source of carbon dioxide and heat. The stacks were built in closed sheds and left for several weeks. Through the combined action of acetic acid vapor, carbon dioxide, and heat/moisture from fermentation, the metallic lead corroded and transformed into basic lead carbonate (white lead). After the corrosion period, the white crusts were removed, washed, and ground for use as pigment.

This form of white lead was prized for its low oil absorption, excellent brushing qualities, high opacity, flexibility, and durability in oil film formation. Despite its superior performance, the process fell out of favor due to its toxicity and labor intensity, eventually replaced by modern chemical synthesis.”

Stages of Skill Development

“The conceptual models used to describe the progression from novice to expert performance across domains. These frameworks attempt to account for qualitative shifts in cognitive control, motor coordination, and knowledge representation as skill proficiency increases through practice and instruction. The most widely cited early model is that of Fitts and Posner (1967), which defines three stages:

Cognitive Stage – The learner understands task requirements through verbal or declarative knowledge. Performance is effortful, slow, and prone to error.

Associative Stage – Performance becomes more fluid through practice. Errors are reduced, and procedural knowledge begins to emerge.

Autonomous Stage – The skill becomes largely automatic, requiring minimal conscious attention. Performance is fast and efficient, though also more resistant to change or adjustment​.

Parallel models (e.g., Anderson’s ACT model) frame these phases as declarative → compilation → procedural, emphasizing changes in how knowledge is encoded and accessed.

More recent research—particularly by K. Anders Ericsson—challenges the notion that automaticity is the final or optimal endpoint of skill development. While the Fitts-Posner model describes a general pathway to functional competence, Ericsson emphasizes that true expertise requires continued effort beyond automatization, through a structured regime of deliberate practice: goal-oriented, feedback-driven activities aimed at performance boundaries​.

Moreover, Ericsson and others caution against equating years of experience with expertise. Without focused refinement and cognitive engagement, skills may plateau or decline—even if practice continues. Hence, while stages offer a useful scaffold, expert performance is increasingly seen as a nonlinear, domain-specific, and individually variable process, deeply affected by metacognitive ability, motivation, and feedback structures​.

In structured training environments like the Waichulis Curriculum, understanding these stages informs task design, feedback timing, and skill calibration. Exercises are scaled to match the learner’s current developmental stage—promoting automaticity when appropriate but always with the scaffolding to re-engage cognitive control when advancing to higher levels of perceptual or technical nuance.”

Standard Observer

“A mathematically defined model that represents the average visual response of a human observer to specific perceptual stimuli under standardized conditions. It is most commonly associated with color science, where it refers to internationally agreed-upon functions that characterize how a typical human with normal color vision perceives visible wavelengths of light. These functions, known as color matching functions, were originally derived from experimental data collected in the early 20th century and serve as the basis for colorimetric systems like the CIE 1931 XYZ color space.

In color vision science, the standard observer is not a real individual but a statistically constructed abstraction based on psychophysical experiments. In these experiments, human participants matched test lights using combinations of primary lights. The averaged results yielded tristimulus values corresponding to red, green, and blue sensitivities, which were then standardized by the Commission Internationale de l’Éclairage (CIE). The most widely used versions are the CIE 1931 2° Standard Observer, which assumes a central field of view of 2 degrees (covering the foveal region of the retina), and the CIE 1964 10° Standard Observer, which accounts for broader field-of-view vision involving parafoveal processing​.

This construct is foundational to modern colorimetry, enabling consistent measurement and reproduction of color across devices and industries (e.g., digital imaging, lighting design, paint formulation). By defining how the average observer perceives spectral energy distributions, the standard observer allows for the objective quantification of perceived color differences, the establishment of color spaces, and the accurate generation of metamers—physically different stimuli that appear the same to human vision​.

The concept of a standard observer extends beyond color vision. In broader perceptual science, it can be used as a reference frame for evaluating perceptual thresholds, discrimination ability, or subjective magnitude estimations under controlled conditions. While useful for experimental design and industrial calibration, it is important to note that individual variation—including age, ocular physiology, and neural processing—can significantly diverge from the standard model, especially in domains like peripheral vision, low-light conditions, or non-Caucasian populations historically underrepresented in early datasets.”

Stand Oil

“A form of partially polymerized linseed oil (partially polymerized, in this context, refers to a partial chemical linking of oil molecules into longer chains, increasing viscosity and altering flow behavior without causing complete solidification) produced by heating raw linseed oil to a high temperature, typically between 525°F and 575°F, and maintaining it at that temperature for an extended period in the absence of air and without the addition of driers or chemical additives​. This thermal treatment induces partial polymerization—a molecular joining of oil molecules—which transforms the oil’s handling and drying properties significantly compared to its raw form.

Through this process, stand oil becomes much more viscous, developing a thick, honey-like consistency. It flows more slowly than raw linseed oil and tends to self-level when applied, minimizing brush marks and producing exceptionally smooth, enamel-like surfaces upon drying. Stand oil dries much more slowly than untreated linseed oil, but the resulting film is notably more flexible, less prone to cracking, and less susceptible to yellowing over time​.

Stand oil does not function effectively as a primary vehicle on its own due to its extreme viscosity and slow drying. Instead, it is typically used in diluted form, often mixed with a volatile (a substance’s tendency to evaporate readily at normal temperatures, often producing vapors that can disperse into the surrounding air) solvent like turpentine or mineral spirits, or incorporated into painting mediums to modify the working qualities of oil paints. When properly used, stand oil can enhance gloss, improve flow, promote leveling, and create a more durable and resilient paint film. It is especially valued for techniques requiring fine blending, transparent glazing, or surface refinement without introducing visible tool marks.

Historically, the use of modified oils, including early forms of stand oil, can be traced to practices of the late Medieval and early Renaissance periods, although the systematic heating of linseed oil under controlled conditions became more prevalent with the technical advancements of the fifteenth and sixteenth centuries. Stand oil became particularly favored in contexts where artists desired smoother, more polished paint surfaces or sought to mitigate the embrittlement and yellowing issues associated with raw oil over long periods​.

Despite its advantages, stand oil must be used judiciously. Its slow drying nature can complicate layered painting processes if not balanced carefully with faster-drying components, potentially leading to adhesion issues or wrinkling if applied excessively over lean underlayers. Additionally, over-reliance on heavily polymerized oils can yield surfaces that are overly glossy or visually inconsistent if not managed properly within the overall material system.”

Stereogram

“A pair or single set of specially designed images that, when viewed using particular visual techniques, elicit the percept of stereoscopic depth from a flat, two-dimensional surface. Stereograms work by presenting each eye with a slightly different image—typically through lateral displacement of corresponding elements—thereby simulating the binocular disparity that occurs naturally when viewing objects at different depths in space​.

The modern stereogram was invented by Charles Wheatstone in 1838, who recognized that the brain could interpret disparities between two planar images as indicators of depth. Wheatstone’s work demonstrated that if two slightly different images—each corresponding to what the left and right eyes would naturally see—were presented simultaneously to each eye, the viewer would perceive a three-dimensional form. Early stereograms required mechanical devices such as stereoscopes, but modern variants can often be viewed unaided using controlled eye convergence. There are multiple types of stereograms:

Standard stereograms consist of simple geometric figures with deliberate positional differences.

Random Dot Stereograms (RDS), pioneered by Béla Julesz (1971), present two fields of randomly placed dots in which a portion of one image is shifted laterally. When fused binocularly, this shifted region appears to pop out or recede in depth, even though no monocular cues to form are present​.

Autostereograms (commonly called ‘Magic Eye’ images) encode both left and right images into a single repeating pattern. When viewed using crossed or uncrossed convergence, these images allow for the perception of depth without special equipment​.

Stereograms have played a major role in the study of stereopsis (binocular depth perception), particularly in evaluating theories about how the brain solves the correspondence problem—i.e., how it determines which parts of the two retinal images belong together. The success of random dot stereograms undermined the ‘shape-first’ theory (which posited that shape recognition precedes depth perception) and supported the ‘stereopsis-first’ hypothesis, demonstrating that depth can be derived purely from disparity information, even in the absence of identifiable forms​.

In experimental settings, stereograms are used to explore perceptual mechanisms, test stereoacuity, and study visual illusions such as motion-in-depth without physical movement. The perception of depth from a stereogram is subject to viewing method (crossed vs. uncrossed), field of view, and individual visual function. Notably, individuals with stereoblindness (often caused by conditions like strabismus or monocular deprivation) are unable to experience the depth illusions elicited by stereograms​.”

Stereoscopic Depth Cue

“(Also called a binocular depth cue) A source of spatial information derived from the slight positional differences between the two retinal images seen by the left and right eyes due to their horizontal separation (interpupillary distance). This binocular disparity provides the visual system with a powerful mechanism for inferring depth relationships and three-dimensional structure—a process known as stereopsis.

Whereas monocular depth cues can operate independently in each eye and are often sufficient for reconstructing spatial layout in two-dimensional media, stereoscopic cues require simultaneous input from both eyes and are available only under binocular viewing conditions. The human visual system matches corresponding features from the left and right retinal images and interprets their positional differences to estimate the relative distances of objects in the scene. This process is most effective within a limited depth range (approximately 2–20 meters) but can offer high precision for depth discrimination, particularly in near-field environments. The primary stereoscopic cue is binocular disparity, which exists in two forms:

Crossed disparity occurs when objects are closer than the point of fixation and are projected outward on each retina.

Uncrossed disparity occurs when objects are farther than the point of fixation and are projected inward.

These disparities are automatically processed by neural mechanisms in the primary visual cortex (V1) and higher-level visual areas, allowing the brain to construct a cyclopean (unified) percept of three-dimensional space from two flat retinal images​.

Unlike monocular cues, stereoscopic cues can convey absolute depth information (i.e., measurable depth intervals), particularly when combined with cues like convergence and accommodation. However, the stereoscopic system also has limits: it relies on sufficient image overlap, matched luminance, and spatial correspondence. Under conditions of visual mismatch, conflicting disparity signals can lead to double vision, rivalry, or perceptual instability.

Stereoscopic cues are critically tested in laboratory paradigms using stereograms, random dot stereograms, and autostereograms to isolate depth perception from other visual variables. The success of these methods—especially random dot stereograms—demonstrates that depth perception does not require identifiable monocular shape information, reinforcing that binocular disparity alone is sufficient to evoke vivid depth experiences​.

In visual training contexts, stereoscopic depth cues are less relevant for static image construction, such as drawing or painting, since stereopsis cannot be encoded in two-dimensional artwork. However, they remain essential for understanding how the visual system interprets real-world environments and are especially relevant in digital rendering, virtual reality, and vision science applications that simulate or exploit depth from disparity.”

Still Life

“A genre or category of visual art—most commonly associated with painting or drawing—in which the subject matter is composed of inanimate objects (though some traditional still life works may include once-living or animate elements—such as insects, fish, or birds—that remain motionless within the composition), often arranged with intentionality to explore form, composition, symbolism, or material texture. Traditional still life subjects include objects like fruit, flowers, glassware, ceramics, books, shells, instruments, and other domestic or organic items that are stationary and do not move on their own.

The term ‘still life’ is an English rendering of the Dutch stilleven, which emerged in the 17th century during the Dutch Golden Age. These compositions allowed artists to demonstrate technical virtuosity and engage with symbolic themes, particularly within the Protestant culture of Northern Europe, where religious iconography was limited. The genre quickly gained prominence for its ability to convey moral, aesthetic, or allegorical meaning through the careful arrangement of ordinary objects. Specialized subgenres include vanitas, which juxtapose opulent objects with symbols of death and decay (e.g., skulls, extinguished candles) to remind viewers of the futility of worldly pursuits​.

In classical Western art, still life was historically ranked low on the hierarchy of painting genres (below history painting, portraiture, and landscape), but it gained increasing prestige through the technical accomplishments of artists such as Caravaggio, Chardin, and the Dutch realists. In modern and contemporary art, the genre has expanded to include nontraditional objects and conceptual frameworks, often engaging with abstraction, material studies, or thematic juxtapositions. It remains a foundational genre for perceptual training due to its controlled conditions, allowing for focused investigation of light, value structure, surface interaction, spatial depth, and compositional balance.

While the traditionally essential criteria for still life include primarily inanimate subjects and intentional arrangement, the boundaries can be flexible. Objects may be natural (e.g., flowers, skulls, shells) or man-made (e.g., bottles, instruments, books), and the compositions may be either purely observational or symbolically loaded.

The correct plural of ‘still life’ is ‘still lifes’, not still lives, as ‘life’ in this context functions as a compound noun (like ‘low lifes’ or ‘flat roofs’). This usage aligns with both modern linguistic practice and traditional art historical convention.

Still life serves not only as an artistic genre but also as a methodological framework for technical development. In the Waichulis Curriculum, for example, controlled still life arrangements provide structured opportunities to hone observational acuity, calibrate mark-making, and explore compositional strategies in both drawing and painting media.”

Stimulus

“Any detectable change in the external or internal environment that elicits a physiological or psychological response from a sensory system. In visual perception, the term refers specifically to the energy patterns (typically light) that initiate neural activity in the visual apparatus, ultimately giving rise to perceptual experience.

The word originates from the Latin stimulus, meaning ‘a goad (annoyance), prick, or incitement’, and has been used in scientific contexts since the 17th century to denote a causative factor in physiological or sensory processes. The correct plural form is stimuli. In perceptual theory, a key distinction is made between two types of visual stimuli:

Distal stimulus: The actual object or event in the external environment that emits or reflects energy (e.g., a chair, a tree, a lamp). It exists independently of the observer and serves as the origin of perceptual input.

Proximal stimulus: The pattern of energy (such as light waves) that directly impinges on a sensory receptor—in the case of vision, the two-dimensional retinal image formed by the projection of light from the distal stimulus.

This distinction is essential because the proximal stimulus is what the visual system actually receives, while perception aims to reconstruct the properties of the distal stimulus. The brain must infer stable properties like size, shape, and identity from inherently ambiguous and variable retinal input—an interpretive task often referred to as the ‘inverse optics problem’​​.

The mode of perception—whether it emphasizes the proximal or distal stimulus—can shift depending on the task or viewer intention. For example:

A representational artist attempting to recreate a scene may train themselves to attend to the proximal stimulus (i.e., the actual retinal image) to better match visual input.

A viewer assessing real-world object properties, like the size of a dessert on a tray, typically engages in distal-mode perception, aiming to interpret environmental conditions rather than the image cast on the retina​. Another example to consider is railroad tracks. The distal stimulus might be two parallel railroad tracks, while the proximal stimulus is the converging image of those tracks on the retina due to perspective projection.

It is important to note that distinguishing between proximal and distal stimuli does not imply that perception grants unmediated access to external reality. All perceptual experience is constructed through complex neural interpretation of sensory input. While the term distal stimulus refers to an object or event in the external environment, the perceiver never directly encounters that object itself but only a perceptual representation based on sensory interaction, physiological constraints, and learned inference. Thus, no mode of perception—whether directed toward proximal or distal characteristics—is inherently more ‘veridical’ in any absolute sense.

Understanding stimulus distinctions is foundational in both perceptual science and art training. In visual arts curricula such as the Waichulis Curriculum, deliberate awareness of proximal stimuli is emphasized in early perceptual training to develop the artist’s capacity for observational accuracy and illusionistic rendering.”

Stippling

“A mark-making technique in which small, discrete dots or points are applied to a surface in varying densities to create the illusion of tone, texture, or form. The primary mechanism behind stippling is tonal variation through spatial frequency—meaning that darker areas are represented by a higher concentration of dots, while lighter areas are rendered with fewer, more widely spaced marks. Unlike hatching or shading with continuous lines, stippling achieves gradation by modulating the distribution and proximity of singular marks.

While often used in pen and ink drawing, stippling is not media-specific and can be executed in graphite, charcoal, paint, or digital platforms. It is particularly associated with monochrome rendering and is valued for its precision, subtlety, and capacity to build texture without smudging or blending. In the context of realistic drawing, stippling can produce finely controlled value transitions and surface qualities, especially when used in concert with other techniques such as cross-hatching or scumbling.

Historically, stippling has been employed since antiquity, but its formal adoption as a tonal rendering method became prominent in engraving and printmaking, particularly in 18th-century European intaglio work. The technique was prized in stipple engraving for its ability to simulate tonal gradation using reproducible dots, predating halftone printing. In the 19th and 20th centuries, stippling also became a favored method in scientific illustration due to its clarity, reproducibility, and resistance to optical ambiguity.

Stippling is often colloquially conflated with pointillism, but the two serve fundamentally different purposes. Stippling is a technique for value modeling, emphasizing tonal control via dot density, usually in monochrome or grayscale. Pointillism, by contrast, is a chromatic strategy based on optical mixing, developed in post-Impressionist painting to achieve color interactions without physical blending. While both use discrete marks, pointillism is guided by color theory and retinal fusion, whereas stippling is governed by tonal calibration and spatial gradation.

In the Waichulis Curriculum, stippling may appear in exercises focused on implied texture, edge modulation, or material differentiation, where control of dot placement sharpens perceptual precision. It is one of several strategies used to build textural gradation, a foundational component of visual realism​.”

Stochastic

“Any process or outcome that is relatively non-deterministic, involving random variability, probabilistic behavior, or uncertain outcomes—even if bounded by constraints or likelihoods. The term originates from the Greek stochastikos, meaning ‘skilled at aiming’ or ‘to guess’, and was historically used in mathematical contexts to describe systems influenced by chance. In contemporary scientific use, a stochastic process is partially governed by probability distributions, making exact outcomes unpredictable even when the underlying rules are known.

In visual arts and perception, **stochastic principles arise when adjustments, constructions, or patterns evolve in response to emergent, non-linear factors—rather than being predetermined by rigid geometric frameworks or analytical pre-planning. For example, stochastic perceptual adjustment is a reactive strategy in which form, structure, or value is guided iteratively by ongoing perceptual feedback, rather than by predictive abstraction​.

This concept is particularly relevant in workflows such as alla prima painting, where artists adapt in real time to changing visual feedback, biomorphic rendering, where organic forms are developed through probabilistic local responses, and compositional improvisation, where the final structure emerges from spontaneous or responsive decision-making, rather than an architectural plan.

Stochastic approaches stand in contrast to analytical construction, which relies on measurable scaffolds and predictive modeling. However, stochasticity does not imply randomness in the sense of chaos; rather, it reflects an adaptive responsiveness grounded in perceptual sensitivity, prior experience, and internalized probability structures.

In perceptual science, stochastic models have been used to explain processes such as visual noise, pattern recognition, and neural variability, where outcomes arise from a distribution of possibilities rather than fixed rules.”

Stochastic Perceptual Adjustment

“A reactive, percept-guided strategy in visual image construction where form, structure, or value relationships are developed through iterative, non-deterministic responses to emergent perceptual cues. Commonly observed in biomorphic or alla prima workflows, this approach emphasizes moment-to-moment modulation based on local visual feedback rather than predefined structural analysis. Such adjustments may reflect probabilistic internal modeling informed by prior perceptual experiences, but lack the predictive scaffolding typical of analytical block-ins or formal abstraction strategies.

Note: The term stands in contrast to analytical simplification and predictive construction, which relies on proactive geometric abstraction and spatial logic. Simply put, Stochastic Perceptual Adjustment is a fancy way of saying ‘I’ll fix it as I go‘.”

Strategic Contrast Deployment

“The purposeful arrangement of light, dark, and color contrast to direct focus, establish hierarchy, and enhance visual impact. Contrast can be achieved through value (light vs. dark), hue (complementary or analogous relationships), saturation (vivid vs. muted colors), and edge sharpness (hard vs. soft transitions). High contrast draws attention to focal points, while lower contrast can create areas of rest or atmospheric depth. Mastering strategic contrast deployment helps control the viewer’s gaze, define spatial relationships, and reinforce compositional intent.”

Stratigraphy

“In the context of art and conservation, stratigraphy refers to the analysis and interpretation of layered structures within a work of art—typically those found in paintings, wall surfaces, or archaeological artifacts. Derived from geological terminology (Greek stratum = ‘layer’, -graphy = ‘description‘), the term originally described the chronological layering of sedimentary rock but has been adapted in art conservation to describe the sequential buildup of material layers over time. In a painting, stratigraphy might involve: support layer (canvas, wood panel, wall), ground or priming (gesso, chalk, etc.), underdrawing or sketch, paint layers (often multiple strata of glazes or impastos), varnishes, dirt, or restoration layers.

Through microscopic cross-sections, X-ray fluorescence (XRF), or infrared reflectography, conservators can study the stratigraphy of an artwork to determine: original versus restored components, techniques and materials used by the artist, chronology of additions or alterations, or degree of degradation or contamination.

Stratigraphic analysis is especially crucial in: authenticating historical works, uncovering underpaintings or pentimenti, or designing minimally invasive conservation treatments.

From a pedagogical standpoint, an understanding of stratigraphy supports informed decisions regarding painting technique, layering behavior, and conservation ethics, particularly when working with historically grounded materials (e.g., oil, tempera, or fresco).

Though the term is not typically used in day-to-day studio instruction, it is foundational in conservation science, technical art history, and the interdisciplinary field of material culture studies​.”

Stratum

“(Plural: strata) A distinct horizontal layer within a structured sequence, often characterized by its material composition, function, or chronological placement. In art and conservation contexts, the term is used to describe individual layers in a multi-phase or multi-material construction—such as those found in painting, printmaking, sculpture, or architectural surfaces. Each stratum in a work of art may serve a unique purpose, including:

Support stratum (e.g., canvas, panel, wall)

Ground or preparation stratum (e.g., gesso, chalk)

Pictorial strata (underpainting, modeling, glazing)

Protective strata (varnish, coatings)

Restorative strata (retouching, overpainting)

In conservation and technical analysis, identifying and differentiating strata is crucial for understanding the material history of an object, assessing its condition, and planning interventions. The term is frequently employed in cross-sectional analysis, stratigraphic diagrams, and layer mapping to describe discrete material intervals in a physically or visually complex object​.

In perceptual training and material literacy contexts, awareness of individual strata reinforces an understanding of how surface phenomena arise from layered interactions—such as translucency, color modulation, or physical depth.”

Strengthener

“In the context of the Waichulis Curriculum, Strengtheners are strategic augmentations to the default sequence of exercises, designed to assist learners who are operating beyond their Zone of Proximal Learning (ZPL). When a student is observed to be struggling with a particular component of the baseline program in a manner that is non-productive—meaning the current level of challenge is yielding diminishing returns or reinforcing error—strengtheners are introduced to temporarily narrow the task demands and focus on a specific sub-skill or operational competency. These targeted interventions aim to scaffold skill acquisition by isolating and reinforcing the underdeveloped capacity, thereby preparing the learner to return to the baseline sequence with increased efficacy. For example, if a student is unable to demonstrate control over the lightest end of the pressure spectrum in an early Pressure Scale exercise, a strengthener might involve repetitive pages of lightest-pressure applications to calibrate tactile feedback and internalize the necessary motor thresholds. In this way, strengtheners function not as deviations from the core curriculum but as empirically grounded supports that increase the likelihood of productive engagement with the baseline trajectory.”

Stretched Canvas / Stretching Canvas

“A textile support (typically linen or cotton) that has been mechanically tensioned and secured over a wooden chassis (stretcher bars) to form a taut, stable surface for painting. The process of stretching canvas involves affixing the fabric to a frame using tacks, staples, or nails, typically beginning at the center of each side and progressing outward to evenly distribute tension. The corners are folded and secured last to avoid puckering or irregularities.

This technique became widely established during the Italian Renaissance, when canvas began to replace wood panels as a dominant support material for oil painting. Linen, valued for its durability, dimensional stability, and absorbency, became the standard material. Cotton—particularly in the form of duck canvas—has since gained popularity for its affordability, though it is generally considered inferior in terms of performance and longevity​.

The typical modern stretching process includes: cutting the canvas several inches larger than the stretcher, centering the chassis on the reverse side of the fabric, using stretching pliers to pull the canvas taut, driving tacks or staples at the center of each side first, then working out toward the corners in an alternating pattern, corners are tucked and fastened last using a technique that minimizes exposed tabs and fits neatly into a frame, and then using keys or wedges inserted into the stretcher corners allow for subsequent re-tensioning without restretching​.

Ralph Mayer emphasizes that while lightweight staples gained popularity after WWII, they are generally inferior to traditional steel tacks, which—due to their corrosion—can actually improve long-term grip in wood. For best results, stretching should be done with moderate, even tension, avoiding distortion of the frame, and ensuring the fabric does not sag or ripple. Unused canvas margins are often folded over and secured at the back to allow future re-stretching if necessary​.

Conservation and material considerations include that canvas is typically sized and primed after stretching to seal the fabric and prepare the surface for painting, and that improper or uneven stretching can lead to warping, cracking, or paint film failure. Also, when using traditional hide glue sizing, it is especially important to avoid over-tensioning, as moisture absorption can lead to distortion. Mayer also notes that backing materials, such as cardboard or barrier cloths, can improve the canvas’s resistance to humidity, dust, and mechanical damage from the rear​.”

Stretcher Bars

“The wooden structural components that form the expandable framework, or chassis, over which canvas is stretched and affixed for painting. They provide mechanical support while maintaining surface tension, allowing a taut, stable working surface. Stretcher bars are typically manufactured in tongue-and-groove style, with mitered corners and beveled edges, and are assembled into a rectangular or square frame using slotted joints. This allows for the insertion of wedges (keys) into the corners to compensate for canvas slackening over time.

Standard stretcher bars are made of kiln-dried woods such as pine or ash, chosen for their dimensional stability. Sizes commonly range from 6 to 60 inches in length, and crossbars (either fixed or keyed) are used in larger formats to prevent warping and add structural rigidity​.

Key features include: beveled edges prevent contact between the bar and the back of the canvas, reducing surface impressions, expandable corners allow tension adjustments via inserted wedges (keys), heavy-duty variants (2½ inches wide) are preferred for large-scale works or conservation purposes, corner bracing devices, such as aluminum or spring-loaded fittings, are used in conservation-grade stretchers for added stability and controlled tensioning.

Stretcher bars should not be confused with strainers, which resemble stretcher frames but lack the ability to expand at the joints. Strainers are considered unsuitable for permanent or professional painting, as they cannot adjust to compensate for canvas movement over time​.

In conservation and framing, proper stretcher selection and tensioning are critical for long-term preservation. Over-tensioning, uneven corner expansion, or the use of undersized or warped stretchers can lead to deformation, paint cracking, and structural damage. In museum and restoration contexts, custom-made precision stretchers with engineered corner systems are often used.”

Striking (Pigment Manufacturing)

“A specific procedure used during the wet stage of pigment manufacturing in which inert extenders or diluents are introduced into a pigment mixture to produce a reduced-strength color. The process is designed to lower the pigment concentration without significantly compromising color integrity, allowing for the creation of lower-tinting formulations that are easier to handle, match, or stabilize across batches. The term is commonly associated with the production of commercial or industrial-grade paints, where cost and consistency must be balanced against chromatic purity.

In contrast to dry mixing—which can result in uneven dispersion or a dull, chalky appearance—wet-stage striking allows for more intimate and uniform incorporation of the diluent, preserving greater vibrancy than dry-added fillers. Struck pigments may still appear lower in chroma than their full-strength counterparts, but they retain a smoother optical appearance and less scattering-based dulling.

This practice is especially relevant when preparing colors for architectural or commercial finishes where full pigment strength is unnecessary or uneconomical. The inert materials used in striking often include substances like barytes, kaolin, or precipitated calcium carbonate, which are chosen for their transparency and minimal reactive interference. As described by Mayer: ‘A reduced pigment is not ordinarily diluted with inert filler by the simple admixture of dry powders, but the inert material is usually introduced during the ‘striking’ of a batch in the wet stage…‘​.

It is important to acknowledge that the term ‘striking’ does not refer to chroma reduction caused by subtractive pigment mixing in studio practice (e.g., combining complementary hues). That type of chromatic change results from overlapping spectral absorption and is best described as chroma loss, dulling, or optical bandwidth narrowing. Using ‘striking’ in that context would be technically inaccurate.”

Structural Color

“A phenomenon in which color arises from the microscopic structure of a surface rather than from pigment absorption. Unlike traditional material color, which is determined by the selective absorption and reflection of specific wavelengths of light, structural color results from light interference, diffraction, and scattering at the nanoscale level. Because it depends on both the physical properties of a material and the way light interacts with it, structural color falls somewhere between material color and radiant color—it is a property of the material’s structure, yet its appearance is dynamic and light-dependent rather than fixed. This effect is responsible for the iridescence of butterfly wings, peacock feathers, beetle shells, and certain minerals, where colors shift depending on the viewing angle. Structural color is often more vibrant and resistant to fading than pigment-based color because it does not rely on chemical dyes but rather on the physical manipulation of light.”

Structural Perspective

“A broad term that refers to any systematic approach used to depict three-dimensional space on a two-dimensional surface through measurable spatial relationships. It encompasses multiple methods, including linear perspective, isometric perspective, axonometric perspective, and curvilinear perspective, all of which establish depth and form using geometric logic. Linear perspective is a specific type of structural perspective that relies on vanishing points and converging parallel lines to simulate depth mathematically, commonly seen in one-point, two-point, and three-point perspective systems. However, structural perspective is broader, also including methods like isometric perspective, which maintains consistent angles without vanishing points, and curvilinear perspective, which simulates fisheye distortions. While linear perspective is the most widely used system for realistic spatial depiction, structural perspective as a whole provides multiple frameworks for organizing space, guiding composition, and reinforcing the illusion of depth in both representational and stylized artwork.”

Stump

“A tightly rolled stick of soft, dense paper used as a blending or smudging tool in dry media drawing—especially with materials like charcoal, graphite, or pastel. Unlike a tortillon, which is hollow and usually pointed at one end, a stump is generally solid throughout, with both ends tapered, allowing for broader or more continuous blending coverage.

Stumps are typically used by rubbing over applied dry media to disperse the material—often in pursuit of homogenous values, softened edges, or smoother transitions. By spreading pigment into adjacent areas of surface tooth, the tool can produce diffused gradients and soft visual shifts without the need for additional pigment application.

Historically and commercially, stumps have been used in both academic and commercial drawing settings, particularly in contexts emphasizing soft rendering or pictorial modeling of form. They are available in various diameters and can be cleaned or re-pointed by sanding.

While stumps are widely available and frequently used by students and professionals, their use in perceptual training programs like the Waichulis Curriculum is explicitly discouraged in foundational exercises. This is due to the fact that: they may compress the tooth of the paper, reducing the surface’s ability to accept further layers of material application, they can obscure stroke-based information, which is critical for learning material placement, directionality, and pressure control, and they can allow for effects without structure (the visual appearance of form or gradation created by smudging or blending without an underlying scaffold of deliberate material placement, directional stroke, or pressure control), potentially undermining the perceptual clarity and control that the curriculum emphasizes. Instead, blending is taught through deliberate material application, tapering, and pressure modulation—techniques that promote visual structure and precise control over value development.”

Style

“An emergent condition that arises from the integrated sum of an artist’s choices, habits, and interactions with their process at every level. Rather than being a predefined set of traits that an artist consciously applies, style is present at the onset as a result of decision-making across materials, techniques, compositions, and execution.

Historically, the term style has most often been used as a manner of distinction between artists, movements, or cultural periods. While this distinction can be useful in classification (e.g., Impressionist style, Baroque style, etc.), it is important to recognize that style is not an isolated attribute but rather the byproduct of an artist’s working methodology, perceptual biases, and material choices. As such, an artist’s style is not something they need to deliberately construct or impose but something that emerges through engagement with their process.

In contrast to technique, which refers to the specific skills and methods used to achieve a result, style emerges from the sum of an artist’s habitual choices and interactions with their process. Technique is a learned or applied approach to execution—such as brush handling, mark-making, or blending—while style is the recognizable, emergent property that arises from the integration of these methods. For example, two artists may use the same wet-in-wet blending technique, but one may habitually apply broad, sweeping strokes while the other prefers short, stippled applications—each producing a distinct stylistic signature.

Style is also distinct from aesthetic preferences, which are a set of biases—both inherent and developed—toward visual qualities like color palettes, subject matter, or compositional tendencies. For instance, an artist may be drawn to high-contrast, dramatic lighting (aesthetic preference), but the ‘whole’ of how they choose to communicate or realize will manifest their style. While an artist can deliberately refine or cultivate certain aspects of their efforts that can direct their style, its manifestation is inevitable—arising from both conscious choices and subconscious tendencies inherent to their process.

Moreover, style can be influenced and refined through training, as education and experience often cultivate specific interactions with process, reinforcing habitual responses that shape an artist’s visual language. For example, an artist trained in a classical atelier may develop a highly rendered, precise approach due to the curriculum’s emphasis on controlled mark-making, while an artist trained in a more expressive program may cultivate a gestural, loose style through habitual engagement with rapid, dynamic strokes. From the moment an artist begins creating, they have a style, as every decision—however refined or unrefined—contributes to the unique fingerprint of their work. Even a beginner who inconsistently applies pressure while adding value with a pencil has a style, however unintentional, simply by virtue of their process. Over time, as techniques evolve and decisions become more deliberate, style may change significantly, but it is never something an artist must ‘acquire’—it is always present in their work.”

Stylus

“A pointed tool traditionally used for inscribing, incising, or marking a surface. In historical contexts, styluses were employed for writing on clay tablets, wax surfaces, or metalpoint grounds. Within the Waichulis Curriculum, the term most often refers to a modern pin vise fitted with a fine compass point, used as a subtractive tool during painting procedures.

This stylus is typically employed to gently remove paint from the surface—often to reveal underlying layers, sharpen edges, define linear accents, or create precise texture—without damaging the ground. The technique allows for additive-subtractive modulation, especially in later stages of indirect painting, where the physical removal of paint can clarify form or enhance spatial transitions.

Proficiency with a stylus in this context requires a high level of surface sensitivity and pressure control, as its function is not to gouge or draw but to selectively subtract with precision. Its use underscores the importance of understanding material response and supports the curriculum’s emphasis on deliberate mark-making and perceptual calibration.”

Subject (Visual Art)

“In visual art, the subject refers to the primary object, figure, scene, or concept being depicted or represented in an artwork. It is what the viewer is meant to recognize or focus on as the central motif of the composition. The subject may be literal (e.g., a person, landscape, or still life), symbolic (e.g., an allegorical figure or narrative reference), or abstracted, but in all cases, it serves as the anchor of representational content. The term is often used interchangeably with ‘content’ or ‘theme’, though distinctions are sometimes drawn:

Subject: what is depicted (e.g., a bowl of fruit, a reclining figure).

Theme: the broader idea or message behind the subject (e.g., mortality, solitude).

Content: the combination of subject, form, and context that yields the artwork’s meaning.

Within compositional analysis, particularly in the Waichulis Curriculum, the subject is addressed not merely as an object of representation but as a node of perceptual organization and viewer engagement. It interacts with elements such as figure-ground dynamics, focal structure, and narrative flow. The placement, scale, contrast, and resolution of the subject relative to its environment govern how viewers perceive hierarchy, emphasis, and intent.

Artists manipulate subject visibility with many aspects of their work, including contrast in value or chroma, edge sharpness, compositional framing, and/or directional cues (e.g., gaze, gesture, line). These choices reflect not only visual hierarchy but also semiotic intent—what the subject stands for in cultural, emotional, or symbolic terms.

The word ‘subject’ derives from the Latin subicere (‘to place beneath’), suggesting something that underlies or supports meaning. In traditional academic painting, the classification of subject matter was foundational to an artistic hierarchy:

History painting (mythology, religion, narrative) was considered the highest genre.

Portraiture, landscape, still life, and genre scenes followed in descending order of intellectual prestige.

Modern and contemporary art movements have challenged these hierarchies, yet the concept of ‘subject’ remains essential to how viewers categorize and interpret visual works.”

Subjectivity (in Art and Perception)

Subjectivity refers to the internal, personal, and often variable experiences, interpretations, and judgments that arise from an individual’s perspective. In the context of art, subjectivity encompasses how artists conceptualize and express ideas based on personal experience, cultural context, emotional state, and individual perception—as well as how viewers receive and interpret those expressions through their own psychological and perceptual filters.

Subjectivity is intrinsic to all artistic activity, as both creation and reception involve an individual’s perceptual and cognitive systems. However, the presence of subjective experience does not preclude objective structure. Artists may impose constraints, goals, or rules (e.g., material limitations, perceptual targets, representational standards) that allow for intersubjective or testable assessments, even within subjective contexts.

While objectivity refers to conditions or judgments that can be evaluated consistently across observers within a defined framework (e.g., perceptual thresholds, material behavior, procedural accuracy), subjectivity involves variables that may shift from person to person (e.g., emotional resonance, symbolic associations, individual aesthetic preferences).

For example: A viewer’s emotional response to a painting is subjective. However, a brushstroke’s length relative to a reference frame (such as a grid, object boundary, or compositional field) can be assessed objectively within a shared perceptual or measurement system.

As philosopher John Searle and cognitive scientists have emphasized, subjective experiences (qualia) are real phenomena, but they are epistemically private—accessible only to the individual experiencing them. This does not invalidate them, but it does distinguish them from public, measurable properties.

In the Waichulis Curriculum, subjectivity is acknowledged as the origin of artistic intention and interpretation, but not as a barrier to structured learning. Instead, the curriculum emphasizes that: artists work within perceptual systems shared across viewers, fluency in objective visual relationships (e.g., contrast, edge clarity, spatial cues) enhances the power and clarity of subjective expression, and that mislabeling empirical constraints as ‘just subjective’ can obscure meaningful structure and hinder skill development.

Subjectivity is often contrasted with objectivity in philosophical aesthetics. Thinkers such as David Hume and Immanuel Kant explored how subjective judgments (e.g., taste) can still aspire to universal communicability—a position that suggests subjectivity does not necessarily entail relativism. Rather, shared biological and cultural frameworks allow for patterned trends in subjective response.”

Subordination (Visual)

“A condition in which one or more visual elements, regions, motifs, or organizational principles are deemphasized, making them less perceptually prominent or attention-demanding than others within a composition. It is a key mechanism in establishing visual hierarchy, functioning in direct relationship to dominance and emphasis.

In practice, subordination is achieved through intentional manipulation of scale, contrast, value, texture, edge resolution, chroma, or placement, such that certain elements recede or yield attention to more dominant components. These visual strategies may be used to support narrative clarity, spatial depth, or compositional balance by allowing dominant elements to emerge without competing distractions.

For example, a background plane may be subordinated through reduced contrast, soft edges, and desaturated chroma to allow a foreground figure to maintain visual prominence. Similarly, areas composed of repetitive textures or low local contrast may serve to stabilize or support the dominance of higher-contrast regions by minimizing competition for visual attention.

Subordination is not a deficiency or loss of importance—it is a compositional strategy that enables clarity by organizing perceptual priorities. Like dominance, subordination is context-sensitive: an element may function as subordinate in one image and dominant in another, depending on its relational attributes.

Subordinate regions often play crucial structural roles by: supporting depth through recession and atmospheric perspective, balancing high-information focal zones with areas of low visual complexity, and anchoring dominant elements via contrast modulation or directional framing.

Much like Gestalt principles of perceptual grouping, subordination contributes to the overall logic and legibility of a composition by establishing zones of relative perceptual weight​.”

Subsurface Scattering (SSS)

“The optical phenomenon in which light enters the surface of a translucent material, interacts internally by scattering and absorbing within its structure, and then exits at displaced locations. This process causes light to diffuse beneath the surface, creating softened edges, subtle glow effects, and blurred transitions between illuminated and shadowed areas.

Subsurface scattering is a defining characteristic of many natural and organic materials, including human skin, marble, wax, leaves, milk, and certain liquids. In these materials, incoming light does not simply reflect off the surface; instead, it penetrates, interacts with internal particles, and exits diffusely, contributing to the material’s distinctive soft, glowing appearance.

In visual perception and rendering, accurately representing subsurface scattering is critical for achieving believable depictions of translucent materials. Artists simulate the effects of SSS through controlled edge softening, subtle internal light transitions, color shifts within shadow masses, and careful value modulation. Understanding subsurface scattering supports more realistic rendering of surfaces where internal light behavior plays a significant role in the observed appearance.”

Substrate

“The underlying material or surface to which an artist applies media, such as paint, drawing materials, or printmaking inks. It includes both the support (structural foundation) and any preparatory layers (such as grounds or primers) that influence adhesion, absorbency, and texture.”

Subtext (Visual)

“The secondary or implied meaning embedded within the visual content of an artwork—not explicitly stated but inferred through contextual, symbolic, or compositional elements. It operates analogously to subtext in spoken or written language, where the literal content (denotation) is accompanied by a layer of connotation shaped by cultural knowledge, semiotic codes, or narrative implication.

In the context of visual communication, subtext arises from the interplay of signifiers, such as gesture, gaze, spatial relationships, object placement, and environmental cues, which together suggest ideas beyond the literal scene depicted. For instance, a domestic interior may show a quiet meal (denotation), but through dim lighting, isolation of figures, and disrupted object arrangement, it might imply tension, grief, or detachment (subtext).

Subtext is shaped by both the artist’s intent and the viewer’s interpretation, and its efficacy depends on shared perceptual and cultural frameworks. It often engages with semiotic connotation, wherein meaning is constructed not from what is shown, but from what that showing implies within a broader communicative system​.

It is important to distinguish visual subtext and symbolism. While symbolism employs culturally recognized icons to reference abstract concepts (e.g., a skull for death), subtext involves implied emotional or narrative layers that may be more ambiguous or contextual. It is not necessarily symbolic in a codified sense but relies on visual suggestion and viewer inference.

The Waichulis Curriculum encourages awareness of subtext in the advanced stages of pictorial development, particularly when visual language fluency supports the intentional deployment of visual relationships. Artists are trained to recognize how compositional elements may be ‘read’ metaphorically or emotionally, even if such readings were not explicitly intended—underscoring the communicative power of visual implication as distinct from direct representation.”

Successive Color Contrast

“A temporal perceptual phenomenon in which prolonged exposure to a colored stimulus alters the appearance of subsequently viewed neutral or differently colored areas—causing them to appear tinged with the complementary hue of the original stimulus. This effect results from chromatic adaptation, a process in which color-sensitive photoreceptors and opponent-process neurons in the visual system temporarily reduce their responsiveness after sustained stimulation.

This phenomenon is commonly experienced as a color afterimage: for instance, after staring at a saturated red patch for several seconds, a viewer who then looks at a white surface may perceive a greenish afterimage in the same retinal location. The effect is a temporal analog to simultaneous contrast, which produces complementary hue shifts across spatial boundaries rather than over time.

Successive contrast originates in part from the opponent-process theory of color vision, wherein certain neurons respond to color pairs such as red-green or blue-yellow. Prolonged exposure to one half of an opponent pair (e.g., red) causes the corresponding opponent channels (e.g., R+G– cells) to become adaptively suppressed. When a neutral stimulus is then viewed, the less-adapted opponent (e.g., G+R– cells) becomes more relatively active, producing the illusion of the complementary hue​.

In visual practice, understanding successive color contrast is critical for anticipating perceptual shifts during prolonged observation (e.g., when painting adjacent color fields), managing unintended afterimage effects during composition or color placement, and designing optical effects or ‘illusions’ that leverage afterimage perception.

Artists may also exploit this phenomenon in color vibration, complementary relationships, or viewer-dependent effects, though its transient nature makes it distinct from fixed, spatial color interactions like chromatic induction or simultaneous contrast.”

Support

“The primary structural material that serves as the backing surface for a painting, drawing, or print. Supports include canvas, paper, wood panels, aluminum composites, and other materials capable of physically bearing the artwork. The choice of support affects mechanical behavior, handling characteristics, and long-term durability.”

Surface Color

“The color perceived from a material based on the selective absorption and reflection of light wavelengths by its surface. Unlike structural color, which results from microscopic interference effects, or radiant color, which originates from emitted or transmitted light, surface color is a property of the material’s pigments or molecular composition and remains relatively stable under consistent lighting conditions. However, it is not entirely independent of illumination—changes in light source, intensity, and surrounding context can alter how surface color is perceived due to effects like metamerism and color constancy. Because it is dependent on the material’s physical properties but does not inherently manipulate or emit light, surface color falls between purely material color and perceptual interactions with light, but remains distinct from dynamic optical effects like structural color. Examples include painted surfaces, textiles, and natural objects like leaves or stones, where color remains consistent from different angles but shifts under varied lighting conditions.”

Surface Normals in Shading

“A surface normal is an imaginary perpendicular vector extending from a surface at a given point, representing the orientation of that surface relative to a light source, viewer, or computational rendering system. In shading, surface normals play a critical role in determining how light interacts with an object’s surface, influencing the placement of highlights, shadows, and reflections. Surfaces that face the light source directly, with normals aligned toward it, receive the most illumination, while those angled away appear darker due to reduced light exposure. This relationship is fundamental to diffuse shading, where light falls off gradually across a curved form, and specular highlights, which appear strongest when the surface normal aligns closely with the reflection vector.

Surface normals also define the angle of incidence and the angle of reflection, which are crucial in light behavior and rendering physics. The angle of incidence is the angle between the incoming light ray and the surface normal, while the angle of reflection follows the law of reflection, stating that light bounces off at an equal but opposite angle relative to the normal. This principle governs mirror-like (specular) reflections, where highly polished surfaces maintain predictable reflections, while rougher surfaces scatter light in multiple directions, leading to diffuse reflections.

Additionally, surface normals contribute to self-occlusion and shadowing, as they define which areas of an object block light from reaching other parts of the form. In computer graphics, surface normals are essential for rendering, especially in normal mapping, where they are manipulated to create the illusion of complex surface detail without increasing geometric complexity. In traditional drawing and painting, an understanding of surface normals allows artists to accurately construct light and form relationships, ensuring that objects appear three-dimensional and visually consistent within an environment.”

Surfactant

“(Short for ‘surface-active agent’) A substance that lowers the surface tension of a liquid or the interfacial tension between two substances—typically between a liquid and a solid, such as water and pigment particles. In the context of art materials, surfactants are critical additives used to improve the wetting, dispersion, and stabilization of pigments and other particulate matter within a fluid binder or medium.

Chemically, surfactants are amphiphilic molecules, meaning they contain both a hydrophilic (water-attracting) head and a hydrophobic (water-repelling or oil-attracting) tail. This structure allows them to surround pigment particles or other solid components, forming structures called micelles. These micelles reduce clumping (agglomeration) and enhance uniform dispersion, which improves color consistency, flow, and film stability.

In modern paints, especially water-based systems like acrylic gesso, surfactants serve to: improve pigment wetting by helping the liquid binder penetrate and surround each pigment particle, enhance adhesion to substrates by facilitating uniform spreading, prevent flocculation (clumping or settling) by stabilizing pigment dispersion, and promote leveling and reduce defects such as crawling or beading on hydrophobic surfaces.

For example, acrylic ‘gesso’ formulations often contain nonionic surfactants to help disperse titanium dioxide and calcium carbonate in the polymer matrix​. Surfactants may be classified as: anionic, cationic, nonionic, or zwitterionic, depending on the electrical charge of their hydrophilic end, while some formulations also use synthetic wetting agents like oxgall analogs or industrial detergents to enhance surface interaction

Excess surfactant or poorly stabilized formulations may lead to problems such as foam formation, film weakening, or unwanted chemical interactions with pigment or binder. As Mayer notes, artists should avoid introducing water or emulsifying agents into oil-based systems unless specifically formulated, as they may promote sponginess, yellowing, or mechanical instability​.”

Sun-Thickened Oil

“A form of linseed oil that has been partially polymerized and oxidized through prolonged exposure to sunlight and air, typically in shallow trays or glass vessels. This treatment increases the oil’s viscosity, drying rate, and leveling properties, making it particularly suitable for glazing mediums and clear varnish applications in oil painting.

The sun-thickening process dates back to at least the 14th century. It traditionally involves mixing linseed oil with an equal quantity of water (sometimes saltwater), then exposing the mixture in a loosely covered container to direct sunlight over a period of weeks. The action of solar radiation and atmospheric oxygen induces partial oxidation, polymerization, and bleaching of the oil. Impurities such as gelatinous or albuminous matter settle or are filtered out over time, often aided by the addition of clean sand to the vessel​.

Compared to raw or alkali-refined linseed oil, sun-thickened oil is more viscous but less so than stand oil. It dries faster and forms a smooth, enamel-like film with minimal brushmarks. It exhibits reduced wetting and pigment-dispersing power, making it unsuitable for grinding pigments. Also, the final color is typically light golden or amber, rather than the ultra-pale tone of heavily bleached oils, which may darken over time.

Unlike stand oil, which is heated in oxygen-restricted environments to achieve polymerization without premature oxidation, sun-thickened oil is exposed to free atmospheric oxygen, leading some to caution that excessive oxidation may reduce its long-term film strength and flexibility, making it behave more like blown oil in some respects​.

Sun-thickened oil has been a preferred component in historical glaze mediums due to its clarity, drying speed, and handling characteristics. When combined with resins (e.g., damar or Venice turpentine), it produces flexible, luminous glaze vehicles ideal for indirect painting methods such as egg tempera or layered oil techniques.”

Surrealism

“A 20th-century avant-garde movement in art and literature that sought to transcend rationalism and traditional aesthetics by accessing the unconscious mind through automatic processes, dream imagery, and irrational juxtapositions. Officially launched with André Breton’s Surrealist Manifesto in 1924, the movement was heavily influenced by Freudian psychoanalysis and Dada’s anti-rational sensibilities.

In visual art, Surrealism is characterized by fantastic, dreamlike imagery rendered with varying degrees of realism. Artists such as Salvador Dalí, Max Ernst, René Magritte, and Leonora Carrington often depicted improbable or symbolic scenes using traditional techniques to heighten the uncanny quality of their subject matter.

Surrealism differs from Imaginative Realism in intent: while both may depict unreal scenes, Surrealism seeks to disrupt logic and reveal unconscious content, often deliberately embracing visual contradiction and symbolic ambiguity, rather than constructing plausible fictive worlds. Surrealism is the realism of the irrational—an attempt to make the unconscious visible through incongruity, automaticity, and symbolic distortion.”

Symbolism

“The use of visual elements—such as objects, figures, colors, or gestures—to represent ideas, emotions, or abstract concepts beyond their literal appearance. A symbol functions as a stand-in or signifier whose meaning is determined by cultural convention, contextual framing, or narrative structure. For example, a skull may symbolize death, a ladder may imply spiritual ascent, and a wilting flower might suggest impermanence.

Symbols can be conventional, drawing on shared cultural or religious knowledge (e.g., serpent = temptation), contextual, assigned meaning by the artist within a specific image or body of work, or personal or idiosyncratic, carrying meaning specific to the creator or audience.

In representational image-making, the strategic use of symbolism enhances semantic density, allowing works to communicate layered meanings alongside perceptual fidelity. However, it is important to distinguish symbolism as a function within a work from allegory, which refers to a systematic structure of interrelated symbols used to express a broader philosophical or moral narrative. A single symbol may operate independently, whereas allegory uses symbolic orchestration to support conceptual cohesion.”

Symbolist Movement

“The Symbolist movement was a late 19th-century literary and visual art movement originating in France and Belgium, reacting against realism and naturalism. Symbolist artists and writers sought to convey internal states, dreams, and metaphysical ideas through poetic, often obscure imagery. In visual art, the movement was marked by mood-driven compositions, mythological references, and the subjective use of form and color to express intangible experiences.

Artists associated with Symbolism—such as Gustave Moreau, Odilon Redon, and Fernand Khnopff—employed representational forms not to describe appearances, but to suggest inner truths or spiritual realities. Though visually distinct from academic realism, the Symbolist movement shares with contemporary representational practice a commitment to intentional form selection and narrative potential, even when symbolic meanings are personally or culturally opaque.”