Lightfastness is a property of a pigment or paint that describes how resistant to fading it is when exposed to light. Light striking a painted surface can alter or break the chemical bonds of the pigment, causing the colors to bleach or change, in a process known as photodegradation. Materials that resist this effect are said to be lightfast.
Some organizations publish standards for rating the lightfastness of pigments and materials. Testing is typically done by controlled exposure to sunlight, or to artificial light generated by a xenon arc lamp. Watercolors, inks, pastels, and colored pencils are particularly susceptible to fading over time, so choosing lightfast pigments is especially important in these media.
- Blue Wool Scale - a measure of dye permanence
- Color fastness - resistance to fading of textile colors
- Fugitive pigment - pigments that are susceptible to fading or altering over time
- Boddy-Evans, Marion. "Art Glossary: Lightfastness". About.com. Retrieved 5 March 2015.
- "Why does ultraviolet light cause colors to fade?". Library of Congress. 23 August 2010. Retrieved 5 March 2015.
- "ASTM D4303-10, Standard Test Methods for Lightfastness of Colorants Used in Artists' Materials". ASTM International. 2010. Retrieved 5 March 2015.
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