What is lightfastness and how is it rated?
The term ‘lightfastness’ refers to a pigment’s ability to maintain its color after prolonged exposure to light. The lightfastness of a paint depends on the pigment, pigment concentration and the vehicle it is mixed with. The degree of color fading in the pigment is measured and rated according to how well the pigment maintains its original color once exposed to light over time.
Pigments are rated by the American Society for Testing and Materials (ASTM). Only pigments rated as class one and two are acceptable for artists’ materials. The pigments that Colors of Nature uses are of class one or two, and denoted by the words ‘excellent’ or ‘permanent’ which reflect our pigment manufacturers’ lightfast ratings.
Other artists’ paint companies produce colors with pigments that are vegetable based, and although these paints are great for temporary use, they will fade with time. Colors of Nature pigments will not fade, and so you can be assured that your efforts producing your artwork will last forever.
Source: Smith, Ray. New Artist’s Handbook, DK Publishing; New York: 2003 print