Scientists study why glow-in-the-dark art and fashion dull over time

By Stephen Beech

Glow-in-the-dark modern art could be prevented from fading as scientists unlock the hidden chemistry behind fluorescent pigments.

Researchers are studying how eye-catching phosphorescent pigments age in the hope of finding ways to preserve the colors for art, fashion and safety applications.

Scientists and museum conservators are uncovering why luminous pigments fade — and how to preserve them for future generations.

Their findings could help protect artwork while informing the development of longer-lasting phosphorescent materials for a range of applications — from fashion runways to airport runways.

The research team explained that most paints and dyes are seen because they bounce visible light back to our eyes.

But fluorescent and glow-in-the-dark pigments absorb light and give it back as a vivid glow, producing the attention-grabbing visual effects found in pop art, fashion, traffic signage and glowing stars used to decorate bedroom ceilings.

Originally developed for commercial and industrial applications, the pigments have since found popularity in art.

Daylight fluorescent materials, such as products manufactured by the Day-Glo Corporation, and glow-in-the-dark pigments begin to appear more prominently in art in the mid-20th century.

But, over time, the materials break down.

And as the colors become duller, the artwork loses some of the eye-catching power that was initially intended.

Sarah Schmidtke Sobeck, from The College of Wooster, Ohio, said: "For artists, the effect isn't simply cosmetic, because they intentionally use these colors for their visual impact."

Gregory Smith, senior conservation scientist at the Indianapolis Museum of Art, added: "Artists have always been attracted to bright, emissive colors.

"They allow you to do exciting things that you just can't do with a regular pigment on the artist palette."

And because fluorescent and phosphorescent materials attract attention and improve visibility, they're also important parts of safety signs and markings.

By understanding how the materials break down over time, the researchers want to help manufacturers develop products that stay brighter longer, such as luminescent paint for airplane runways.

The duo has spent years studying daylight fluorescent and phosphorescent pigments through a collaboration that began 10 years ago when they met at a cultural heritage science conference.

Their work initially centered on testing the emission of light from samples in the Indianapolis Museum of Art, which features fashion with bold fluorescent colors and designs.

They are due to present their findings at a meeting of the American Chemical Society (ACS) in Chicago.

Sobeck will share new findings from her studies of glow-in-the-dark phosphorescent pigments.

She first identified what the materials are made of before the team examined the pigments' photophysics — how they absorb, store and emit light — and how the processes change as the materials age.

The researchers found that many phosphorescent materials contain inorganic compounds and mineral-based pigments and differ "significantly" from the organic dyes commonly used in fluorescent colorants.

Sobeck said that one of the most surprising findings is that prolonged exposure to high levels of humidity can play an equally important — and sometimes greater — role than prolonged exposure to ambient light in breaking down phosphorescent pigments.

She said the discovery will lead to "improved storage and exhibition conditions."

Earlier studies of fluorescent pigments from the Sobeck lab revealed that the compounds responsible for enhancing brightness — called optical brighteners — degrade faster than the pigmentary dyes themselves.

As a result, colors appear to darken even when the pigment molecules remain intact.

Sobeck says the results also highlight why conserving modern artworks can be challenging.

She explained that conservators restoring fluorescent artworks must match colors under both visible and UV light, while the pigments themselves continue to change over time, making long-term restoration difficult.

Sobeck said: "I've been able to establish a lot of different opportunities for students who are pursuing double majors in art history and chemistry, or chemistry students who are really interested in seeing how they can apply their studies to different real-world scenarios."

She added: "It shows how chemistry and art can come together to answer important questions."