Inorganic – Discovered in Berlin in 1704 and introduced through the early 18th century. Prussian Blue is one of the first synthetic inorganic pigments and also one of the most controversial. The earlier and less purified versions had a mixed reputation; said to fade in hues, migrate or leech through succeeding paint layers. But modern standards of washing have dispensed with the tendency to fade, and the migratory properties ascribed to this colour are no longer reported. I suspect that this was the result of poor stabilizing. At any rate, Prussian Blue, like Alizarin, is one of those colours some painters find essential. It has a great deep inky beauty. On its own and in more concentrated mixes it exhibits a slight bronzy sheen which can be used almost like a complementary glaze. Its Tint Power is frightening so beginners beware!