Light, Materials, and Human Observation and Judgment

In long-term observations of materials such as alcohol inks, pigment powders, solid watercolors, acrylics, and oil pastels, light sources—whether natural light or artificial lamps—cannot be simple categorized as "affecting materials" or "not affecting materials." Whether a material changes depends on its own attributes, the stage it is in, and the intensity and duration of light exposure.

The role of light within these material systems can be clarified into three distinct levels:

1. Light as the basic visibility premise for observation to occur;
2. Light's effect on human perception and visual judgment;
3. Light's direct action on the state of certain materials over longer time scales.

1. Light as the Basic Condition for Observation

Without sufficient visibility, human observation of material behavior cannot take place.

If an environment is completely dark (such as at night without lighting or in an unlit enclosed room), even if movement, evaporation, settling, structural changes, or moisture loss are occurring within or on the surface of the material, these processes cannot be perceived by the human eye.

In this situation, the inability to gather information does not mean the material's behavior has stopped; rather, human observational capability has temporarily failed. Light here acts as an external condition that allows observation to exist, rather than an active participant in material behavior, nor does it directly create dips, air bubbles, cracks, hollow spaces, or dried states.

2. Specific Expressions of Light Across Different Material Systems

1. Alcohol Inks

• Sealed Storage Stage: Alcohol inks and volatile reagents stored in sealed bottles or closed containers show no particularly obvious visible changes under long-term indoor lighting. However, changes have been observed in some inks left outdoors over extended periods.
• Open Behavior Stage: Once ink is taken out and placed on an open surface, its behavioral window usually lasts only a few minutes. Within normal observation time scales, light itself has not been observed to cause immediate changes in ink movement or color. Because liquid surfaces reflect light easily, strong light or specific lamp angles alter the colors, edges, and local structures seen by the eye. A person must adjust their viewing angle to get a clear visual, meaning light here affects visual observation and angle selection.
• Long-Term Preservation Stage: Once a piece is finished and exposed to strong light and ultraviolet rays over long periods, the resulting work may undergo color changes, fading, or even partial detachment due to altered surface adhesion.

2. Pigment Powders and State Transformations

• Sealed and Raw Powder State: The stability of pigment powders under long-term light exposure depends on the inherent lightfastness of the pigment itself. Pigments with strong lightfastness remain stable under long-term indoor and outdoor observation, while pigments with weak lightfastness show color changes over time.
• Medium for Judging Material State: In observations without a fixed recipe where binding states are judged through physical testing, a small sample can be taken and dried. By observing differences in surface reflection under light, a person can tell whether the sample presents a matte, semi-matte, or slightly glossy surface, using this to judge if the mixture is close to the expected state. At this stage, light acts as a medium for state identification.
• Grinding, Pouring, and Curing Stages: Light primarily provides visibility, allowing a person to identify powder particle states and check for structural anomalies during curing—such as dips, air bubbles, cracks, internal hollows, or uncured areas.

3. Solid Watercolors

• Painting Stage: Light mainly serves visual recognition. Colors with special visual shifts, such as metallic or chameleon shades, are difficult to perceive when light is dim or the angle is restricted. Light ensures that a person can recognize colors, light-and-dark relationships, surface finishes, and fine details. Within normal painting timeframes, light has not been observed to directly alter watercolor paint behavior.
• Long-Term Preservation Stage: Under long-term exposure to strong light or sunlight, pigments with weak lightfastness fade or change color. Additionally, the substrate itself (such as paper) may yellow or change color over time under light exposure, and changes in the substrate alter the final overall visual result.

4. Acrylics

• Working Stage: Light provides visibility to observe fluid movement, spreading, cell structure, and surface finish. Cell formation, sheen, or coverage on acrylic surfaces stem from internal relationships within the material itself, rather than being created by external light.
• Long-Term Preservation Stage: Acrylics possess high opacity and coverage. In existing long-term observations, light exposure has not caused particularly obvious color changes, showing relatively stable long-term performance.

5. Oil Pastels

• Working Stage: Oil pastels have high opacity and present no significant surface glare issues, eliminating the need to frequently change viewing angles during observation. Light serves solely to satisfy the need for recognizing colors and canvas states.
• Long-Term Preservation Stage: In multi-year observations under exposure to air and normal light, oil pastel colors have not shown noticeable color changes, indicating that direct impacts from light are quite limited.

3. Indirect Impact of Light Color and Intensity on Human Judgment

Beyond light intensity, the color of light (such as warm light versus cool light) is another key variable.

Warm and cool lights have not been observed to directly alter the physical behavior of these materials, but they do alter the visual color information received by the human eye. The same color produces different color perceptions under warm light sources compared to cool light sources.

This perceptual shift changes the visual information received, which in turn leads to changes in human judgment. This causes a person to alter their method of intervention and subsequent choices, ultimately creating differences in how the work turns out.

The final differences in a work stem from human behavioral changes triggered by visual input, rather than the material automatically altering its behavior under light.

4. The Three Levels of Light's Action Mechanism

Based on the above observations, the role of light in material systems can be divided into two paths and three distinct levels:

1. Classification of Action Paths

• Direct Path: Prolonged light exposure directly causes changes in the state of the material or substrate (e.g., long-term strong light causing fading, detachment in alcohol inks or watercolors, or paper yellowing).
• Indirect Path: Lighting conditions (intensity, angle, or color) affect the visual information received by a person, altering human judgment and subsequent operational choices, which ultimately creates differences in the material's final presentation.

2. Three Distinct Levels

• Level 1 (Visibility Premise): Provides basic observational conditions, determining whether material behavior "can be seen."
• Level 2 (Perception and Judgment): Alters viewing methods and judgment choices by changing surface glare, color presentation, or highlighting fine surface details.
• Level 3 (Long-Term State Changes): Directly alters the state of certain materials and substrates over extended time scales under specific light exposure (such as strong light or UV rays).

Being unable to see does not mean material behavior has stopped; a change in visual perception is not the same as a material itself changing; and color fading or detachment under years of light exposure is a separate time-scale issue entirely distinct from daily operational observation.