Organic Pigments Inorganic pigments are based on metals, mostly in the form of oxides, sulfides or silicates. Organic pigments are based on carbon, hydrogen, oxygen and nitrogen and are metal free. The only remaining naturally occurring pigments are the Siennas and Umbers. The vast majority of pigments are synthetic, that is, chemically made by man.
All organic pigments are synthetic.
Lightfastness Rating Lightfastness is the ablility of a pigment to resist fading. In these cases, data from pigment manufactures and our own test facilities have been used and an appropriate description assigned under Permanency. The identified colors are sensitive to a combination of moisture and Ultra Violet radiation and are not recommended for outdoor use . For example, PB 60, Anthraquinone Blue, indicates a specific Pigment Blue. The C.I. Number is a five-digit reference number assigned in the Colour Index based on the chemical structure of a colorant, regardless of usage class.