“A translucent deep black-blue oil color with high tinting strength, fine-grained and a 'short' buttery paint. Also known as Berlin blue, Paris blue, Antwerp blue, and Chinese blue, Prussian blue is the earliest modern synthetic color. (Gettens, 149–151) It is a complex chemical compound, ferric ferrocyanide (Fe4(Fe[CN]6)3), first mentioned in 1710, but its preparation was kept secret until 1724. A London manufacturer named Wilkenson began production, and gradually more and more color firms followed suit. By 1750, Prussian blue must have been well known all over Europe. (Gettens, 151) Long before that, however, Prussian blue was in use in the United States.” -Natural Pigments