Light and color degradation: 

why colors are not permanent?

Color feels like one of the most stable properties of the world. We look at a painting, a printed page, or a piece of fabric and assume that its color is a fixed feature of the object itself. In reality, color does not exist as a stable property. It is a temporary perceptual effect created by the interaction of light, material structure, and the human visual system.

What we perceive as red, blue, or green is not “inside” the object. It is the result of certain wavelengths of light being absorbed while others are reflected. The brain then interprets this reflected light as color. This means color is never truly fixed it is always dependent on external conditions.

Because light, materials, and environments constantly change, color itself must also change over time.

What color actually is?

Color is not a substance or a material property in the traditional sense. It is a physical and perceptual phenomenon based on selective light absorption and reflection.

Every pigment works like a filter:

• it absorbs specific wavelengths of light,

• it reflects others,

• and our eyes interpret the result as a specific color.

However, this system is extremely fragile. If the chemical structure of a pigment changes even slightly, its interaction with light changes as well. As a result, color does not “age” on its own the material producing it does. In this sense, color is a process rather than an object.

UV light the invisible destructive force

One of the most important factors responsible for color degradation is ultraviolet (UV) radiation, a component of sunlight that is invisible to the human eye.

UV radiation acts as a microscopic разрушive force:

• it carries high-energy photons,

• it breaks chemical bonds in pigments,

• it triggers oxidation reactions,

• and it permanently alters molecular structures.

As a result, pigments are no longer the same chemical compounds they once were. Their ability to absorb and reflect light changes, which we perceive as fading, discoloration, or shifts in hue.

Importantly:

• different pigments respond differently to UV exposure,

• some degrade within months,

• others remain stable for decades.

Color stability is therefore never absolute—it is always conditional.

Differences between materials

Watercolor

Watercolor is one of the most sensitive media. Pigment is suspended in gum arabic and applied in very thin layers.

• high transparency,

• minimal protection of pigment particles,

• strong sensitivity to UV light,

• rapid fading in exposed conditions.

The quality of pigment plays a major role—two visually identical colors may age very differently depending on their chemical composition.

Oil Paint

Oil paint forms a thicker, more protective film.

• pigment embedded in drying oil,

• slower oxidation processes,

• better structural stability over time.

However, oil paint has its own issues:

• the oil binder may yellow,

• transparency can change over time,

• the surface can become brittle or uneven with age.

 

Acrylic Paint

Acrylic paint is a polymer emulsion that forms a flexible film after drying.

• relatively strong mechanical durability,

• good pigment stability (depending on quality),

• resistance strongly dependent on formulation.

Cheaper acrylics often contain less stable pigments, which leads to faster fading.

Pencils (Graphite and Colored)

• graphite is extremely chemically stable,

• colored pencils depend on pigment quality and binder composition.

Colored layers can fade if pigments are organic or poorly stabilized.

Pastels (Soft and Oil-Based)

• soft pastels: almost pure pigment, extremely vulnerable to light and smudging,

• oil pastels: more stable binder, but still dependent on pigment quality.

Because soft pastels are minimally bound, they are among the most light-sensitive artistic materials.

Markers (Water-Based, Alcohol-Based, Permanent)

• water-based markers: least stable, highly prone to fading,

• alcohol-based markers: better penetration and moderate durability,

• permanent markers: resistant to water but not necessarily to UV radiation.

“Permanent” refers to resistance to one type of influence, not permanence in absolute terms.

Paper and substrates as co-factors of degradation

Color never exists alone it always exists on a substrate that actively influences its aging.

Paper

Paper is one of the most important factors in color degradation.

• wood-based paper contains lignin → yellowing over time,

• acid-free paper is more stable,

• cotton-based paper (rag paper) is highly durable,

• bamboo and other plant fibers vary in long-term stability.

Manufacturing processes also matter:

• handmade paper often ages differently due to irregular fiber distribution,

• industrial paper may contain additives that accelerate aging.

 

Wood, Canvas, and Other Surfaces

Color is also shaped by mechanical and environmental movement.

• wood expands and contracts with humidity,

• canvas tension changes over time,

• natural fibers respond to temperature and moisture fluctuations.

This means artworks do not only chemically age they physically transform.

Why two "identical" works age differently?

Even if two works appear identical at creation, they will never age in the same way.

Factors include:

• pigment manufacturer (chemical purity differences),

• binder composition (oil, acrylic, resin variations),

• layer thickness (affects oxidation and light penetration),

• light exposure intensity and duration,

• humidity levels,

• temperature fluctuations,

• air quality (pollution, dust, chemicals),

• microenvironment (frame, wall, storage conditions).

As a result, “identical” objects diverge immediately after creation. Each begins its own unique aging trajectory.

Color as a record of time

Instead of thinking of color as a fixed property, it can be understood as a record of environmental history.

Color becomes a form of documentation:

• intensity of light exposure,

• duration of exposure,

• humidity and air composition,

• chemical composition of pigment and binder,

• material history and interaction with its environment.

Every fading process is not just loss it is information.

In this sense, materials “remember” their environment physically, not symbolically.

Natural vs synthetic pigments

Not all colors are built the same way.

Natural Pigments

Natural pigments come from minerals, plants, or organisms.

• often chemically complex,

• variable composition between batches,

• sometimes highly stable (mineral-based pigments),

• sometimes highly unstable (organic plant dyes).

They tend to age in irregular, uneven ways due to their complex molecular structures.

Synthetic Pigments

Synthetic pigments are industrially engineered.

• controlled chemical composition,

• designed for consistency and stability,

• often more UV-resistant,

• predictable aging behavior.

However, not all synthetic pigments are durable cheap formulations may degrade quickly.

In general:

• natural pigments → more organic, irregular aging patterns,

• synthetic pigments → more uniform or abrupt degradation.

 

Oxidation – the Ssilent transformation

If light is a sudden destructive force, oxidation is a slow and continuous one.

Oxidation occurs when:

• oxygen reacts with pigments, binders, or substrates,

• energy (light or heat) accelerates the reaction.

Effects include:

• yellowing of surfaces,

• loss of elasticity in paint films,

• increased brittleness,

• changes in transparency.

Oil-based media are especially affected, as drying oils continue to oxidize long after the artwork is finished.

Oxidation is independent of light but light significantly accelerates it.

Mold, moisture, and biological degradation

Materials are not only chemical systems they are also biological environments.

Mold

Mold develops when:

• moisture is present,

• organic material is available,

• air circulation is limited.

Effects:

• breakdown of cellulose fibers,

• permanent staining,

• structural weakening,

• irreversible surface damage.

Mold does not attack color directly it consumes the material that holds it.

Insects and Microorganisms

Depending on conditions, materials may also be affected by:

• insects feeding on paper or fibers,

• silverfish consuming cellulose,

• bacteria breaking down organic binders.

Highly vulnerable materials include:

• old books,

• untreated paper,

• natural adhesives,

• unsealed canvases.

In these cases, materials are not just aging they are being biologically decomposed.

Material as a degradation ecosystem

When all processes are combined, a material becomes a complex system shaped by:

• light (photochemical degradation),

• oxidation (chemical transformation),

• humidity (structural instability),

• biological activity (mold, insects, microbes),

• pigment chemistry (intrinsic stability),

• substrate properties (paper, canvas, wood).

Every object is therefore a small ecosystem transitioning from stability to dispersion over time.

 

Color does not disappear. It transforms until it is no longer recognized as the same. What we call degradation is actually continuous material change driven by light, chemistry, biology, and time. Interestingly, a similar process happens in human vision. With age, the eye’s lens becomes slightly yellowed, and retinal sensitivity changes. Colors are perceived differently over time not only because the world changes, but because we change as observers. Color was never stable. Stability was only a temporary illusion created by a brief moment in time.