Thursday, December 20, 2007
I'm not sure when ASTM assigned numbers to pigments, but it has been some time ago. Originally they did their testing for automotive and commercial paints. When they turned to artists' colors, I think it sort of whacked artists over the head. It was a shock to discover that so many of their favorite colors were fugitive or had fugitive pigments in their mixtures. ASTM set a voluntary standard for paints and paint labeling and quite a few manufacturers have complied by listing this information on their paint labels. Most are U.S. producers. The Color Index Names (which are actually letters and numbers, e.g., PR 254 means "pigment red, number 254," which is pyrrol red)are useful, but brands may look different, even with the same pigment. One of the more consistent colors is phthalocyanine blue green shade, PB 15:3, which has a different name in every brand of paint. It can be a challenge if you run out of paint and try to match a color, but you have a better chance if you know the ASTM name.