Colour Ageing and Conservation

Why colour fades, yellows and darkens, how conservators measure and slow it, and what light exposure actually costs a painting, a photograph or a curtain.

Explains mechanisms and published conservation guidance. It is not a substitute for a conservator's assessment of a specific object.

14 topics · 63 evidence-labelled claims · 37 sources

Tools

Light exposure calculator

How colour changes

Photodegradation, oxidation, hydrolysis and migration.

Why do colours fade in light, and why does ultraviolet do so much damage?A colourant fades when the molecule that absorbs light is broken or changed so that it no longer absorbs.Why do so many materials turn yellow as they age?Yellowing is usually the first visible sign of oxidation.Why do colours bleed, run or transfer, and which materials are most at risk?Bleeding happens when a colourant that should stay put can move — dissolving in water, softening with heat or diffusing through a…

By object

Paintings, textiles, photographs, paper and plastics.

Why do old paintings look yellow and brown, and is it the varnish?Often it is.Which pigments change colour in old paintings, and what happened to Van Gogh's yellows?Some historic pigments change chemically long after the painter finished.Why do fabrics fade so quickly, and how long can a textile be displayed?Textiles combine the most light-sensitive colourants — many natural and early synthetic dyes — with fibres that light also weaken…Why do old colour photographs fade and turn orange or magenta, even in albums?Most colour photographs are chromogenic: their image is three layers of dyes — yellow, magenta and cyan — formed during processin…Why have so many colour films faded to pink or magenta?From 1950, most colour films were shot and printed on chromogenic Eastman Color stock, whose cyan and yellow dyes were unstable a…Why do newspapers and old books turn yellow and brittle?Mostly because of what the paper is made from.Why do white plastics turn yellow, and why do some yellow while others just crack?Plastics yellow when light, heat and oxygen create colour-absorbing structures in the polymer or its additives.

Protection and measurement

Light limits, lightfastness testing and display.

How much light can a sensitive object take, and how do museums budget it?Museums increasingly treat light as a budget measured in lux-hours rather than a fixed ceiling.Does UV-filtering glass stop art and fabrics from fading?It removes one important cause of damage, but not the main cause of fading.Why does exterior paint fade, chalk and lose its gloss?Outdoors, sunlight, oxygen, heat and water act together on a paint film.How is lightfastness tested, and how reliable are accelerated tests?Lightfastness is tested by exposing a sample to intense, filtered light alongside reference materials — classically the eight blu…