|
Definition: The length of time a pigment retains its original colour. Pigments must be light-fast (not fade when exposed to daylight) and must not react chemically with other pigments and materials used in paintings nor the atmosphere.
A tube of paint is likely to have an indication of the permanancy of the pigment on it. For example, the American Society for Testing and Materials (ASTM) rates lightfastness of pigments as: ASTM I = excellent; ASTM II = very good; ASTM III = may be satifactory if applied full strength.
Another term for a pigment that isn't permanent is fugitive.
