What if colors never faded?

Some things lose their color in the sun. A red poster can turn pink.

What if colors never faded? Would everything stay bright forever?

Have you seen a shop poster that has been in a sunny window for a long time? The reds turn pink, the blues go pale, and some colors disappear almost completely. Curtains, book covers and toys can fade in the same way.

So what if colors never faded? Would paintings, clothes and photos stay bright forever? To answer, we need to know what light does to colors in the first place. In this lab we follow three clues: sunlight and dyes, long-lasting paints, and blocking ultraviolet light.

Fading is one of the commonest forms of light damage. Conservation scientists at the Canadian Conservation Institute (CCI) describe it plainly: light fades, or bleaches, colors, and the fading is irreversible. The Library of Congress adds that light damage is cumulative.

This thought experiment imagines colors that never fade and asks what that would take. It follows three threads: how light breaks down colorants, why some pigments last centuries while others vanish in hours, and why blocking ultraviolet helps less than many people think.

Sunlight is very bright. Bright light slowly changes some colors.

Once a color has faded, it does not come back.

Fading happens because light carries energy. When a colored material soaks up light, some of that energy can change its colored molecules, so they no longer show the same color. Each bit of light does only a tiny bit of damage, but it adds up. The Library of Congress explains that dim light for a long time can do as much damage as bright light for a short time.

Some colors are very fragile. Conservation scientists say some felt-tip pen inks can fade in just a few hours of direct sunshine. Once faded, a color does not come back.

Light damage is cumulative and follows the reciprocity principle: the total exposure, intensity multiplied by time, is what counts, so dim light for a long time is as damaging as bright light for a short time (Library of Congress). CCI notes that the rate of damage rises with intensity: about 1,000 times higher in sunlight than at good museum lighting levels.

The range of sensitivity is enormous. According to CCI, the most fugitive colors, such as some felt-tip pen inks and some color photographs, can disappear within a few hours of direct sunshine or a few years under low museum lighting. And the damage is irreversible: there is no true recovery for faded colors.

Imagine every color stayed bright forever.

Old paintings and clothes would look new. Museums could use bright lights!

Now imagine that colors never faded. Museums could light their paintings, old fabrics and photos brightly and show them all the time. Today, many museums keep fragile things in dim light, or display them only for a while, to slow the fading.

Old flags, quilts and posters would look as bright as the day they were made. A sunny window would be a safe place for a drawing. These are ideas, not facts: no one knows exactly what a fade-proof world would look like, but we can reason about it.

In a fade-proof world, the central dilemma of museum lighting, seeing versus saving, would ease. Today conservators ration light: CCI describes 50 lux as the benchmark adopted for museums, a level at which a young viewer sees most details well. The Library of Congress notes that sunlight is generally avoided for displaying light-sensitive items, and that each item's cumulative exposure should be recorded when guidelines are exceeded.

With colors that never faded, those trade-offs might disappear for color, although UV would still yellow and weaken paper and textiles. But there is a deeper catch. CCI points out that the photochemistry of colorant fading happens in the same band of photon energies our retinas use to see. A color that absorbs light is, by its nature, absorbing the energy that can change it.

Some colors come from rocks and minerals. They hardly fade at all.

Colors from many plants fade much faster.

Not all colors are equally fragile. Conservation scientists in Canada sort them by how fast they fade. Most colors made from minerals, the colors fired onto pottery and glass enamels, and many modern paints made for cars and outdoor signs hardly change in light at all.

Others fade quickly: most bright dyes made from plants, colors made from insects like cochineal, most felt-tip pens, and most red and blue ballpoint inks. So a world where colors never faded would need all colors to act like the tough mineral ones.

CCI's sensitivity table makes the pattern clear. Materials with no light sensitivity include most (not all) mineral pigments, the true fresco palette, glass enamels and ceramics. Low sensitivity includes many high-quality modern pigments developed for exterior use and automobiles, and materials rated ISO Blue Wool 7 or 8. High sensitivity includes most plant extracts, and so most historic bright dyes, insect extracts such as cochineal, most early synthetic colors such as the anilines, most felt-tip pens and most red and blue ballpoint inks.

The Blue Wool standard used to rate lightfastness is a set of eight blue-dyed wool cloths. The Library of Congress explains that each needs about twice as much light as the one before to fade to the same degree.

Some light is invisible. It is called ultraviolet, or UV.

Blocking UV helps a little. But ordinary light fades colors too.

Ultraviolet light, or UV, is invisible to us. Museums often use special glass or filters that block it, because UV makes paper and fabrics yellow and weak. We don't need UV to see, so blocking it doesn't make anything harder to look at.

But here is a surprise. Many museums and collectors have assumed UV is the main cause of fading. Canadian conservation scientists explain that for colors that fade easily, UV usually causes less than half the fading, and often only about a tenth. The rest comes from ordinary visible light, the light we need to see the colors at all. That's why museums also keep the lights dim.

The Library of Congress advises removing UV and infrared from display lighting, or using UV-absorbing glazing, because they drive deterioration without helping vision. UV causes yellowing, chalking, weakening and disintegration of many materials.

But CCI is explicit that a UV filter alone will not stop fading. Many museums, private donors and framers have assumed UV is the primary cause of fading; in fact, for light-sensitive colors, UV usually contributes less than half of the fading and often only a tenth. The Library of Congress agrees that visible light, even with all UV and infrared removed, is still damaging and must be controlled. CCI concludes that to reduce fading from display lighting there is only one option: reduce light exposure.