The industry standards for lightfastness have been established by the American Society for Testing Materials (ASTM), which does very rigorous testing. The ratings range from Class I (very lightfast) to Class V (very fugitive).
Alizarin crimson has been a popular pigment in many art media since it was first synthesized in 1868. But it has received an ASTM rating of III or IV. It will eventually fade out of any painting that is exposed to the light.
These test samples were conducted by Bruce MacEvoy of handprint.com, an excellent website for color information. The right half of each swatch shows alizarin crimson watercolors after an exposure of 300 hours of sunlight. The brands, from left to right, are Winsor & Newton, Daniel Smith, Holbein, M.Graham, Rembrandt, Rowney Artists, Sennelier.
Genuine alizarin crimson can be identified by the color name of PR 83. Several manufacturers still offer PR 83 alizarin in all painting media in the name of being traditional, but they shouldn't.
And artists shouldn't use it, even if it was a favorite color of our artist-ancestors.
There are several replacements, which nearly match alizarin crimson’s hue and transparency. They’re sometimes called “permanent alizarin” or “alizarin hue” and they tend to come from the quinacridone, pyrrole, or perylene families, and include such names as PR 202, PR 176, PR 206, PR 264 and PV 19.
Tomorrow I’ll offer some web and book resources to suggest what you can do, and how you can find out more about other pigments.
Handprint.com on Alizarin