PY138

Quinophthalone Yellow, also known as Sulphur Yellow. It's lightfastness varies depending on the source- some list it as ASTM II and others reported as excellent. It's recommend to do one's own tests. The toxicity is reported as A, so the lower tier of concern. This is a fairly rare pigment in oils, however it can be found from Holbein and Vasari.

Vasari describes it as a cool yellow which mixes gently with others and they include it in their Basic Yellow, along with offering it as a single-pigment paint. In particular, they mention that it doesn't lighten a mix like a Cadmium Yellow can. On the other hand it also does not have as high of chroma as a cadmium, and is likely less lightfast than cadmiums. We have heard it described as a light bright yellow which differs from Vasari's description. In watercolors it does appear very bright in some brands.