Blockx Indigo Oil Paint, 35ml Tube Indigo no255 is a semi-transparent color ground with linseed oil Blockx oils are the highest quality, made by the blockx family in belgium since 1865. highest grade pigments are ground on slow turning stone mills All colors are lightfast, there are no fugitive colors such as alizarin crimson. pigments are ground with either poppy Blockx Earth Colors are famed for their richness, often copied by other manufacturers using lower grade pigment Blockx does not produce any colors in hues, tones/tints, all fillers, extenders, and driers are excluded the paint is nothing but pure pigment and oil