Pigment PowdersNote on making oil colours. Every pigment requires a different volume of oil to bring it to the desired consistency. This varies enormously so that a pigment like Alizarin, for instance, requires almost twice as much oil by volume as White Lead. In practice, therefore, it is advisable to avoid fast-drying colours in high oil content such as Umbers, Siennas and Cobalt Blues in underpainting unless they are applied thinly or in tints reduced with white. Toxicity Ratings: The Classifications used are based on those intended for guidance of artists’ colour manufacturers where large quantities might be involved. The risk for an artist using small amounts of colour is therefore comparatively small. Dust masks, however, should be worn. Code: A - Non-hazardous. B - Relatively harmless. C - Very low toxic hazard – some precaution necessary. D - Defined physiological hazard – appropriate precautions necessary.