ASTM D 50676
Standard Specification for Artists' Watercolor Paints

This specification is nearly the same as ASTM D 4302, but applies only to transparent watercolors. There are testing, performance and physical property requirements for these paints that make them different from those covered by D 4302. For instance, transparent watercolor colorants are not required to be mixed with a standard white paint but instead are made into transparent samples on a specified neutral paper.

Since the transparent watercolor paints are considerably more sensitive to color changes than oil paints, the colorants that pass the lightfastness test for this standard is a great deal shorter that the one found in oil, resin-oil and alkyd paints.

The same caveats regarding conformance and labeling terminology, used in the description of ASTM D 4302, applies to this standard.