In 1704 the dye-maker Johann Jacob DiesbachIt made a chance discovery that characterizes so much of the history of artists’ colours and in the process invented the rst modern, arti cially manufactured colour.

Working in his Berlin laboratory on a cochineal red pigment, he disregarded the fact that one of his raw materials, potash, had been contaminated with animal blood. In the belief that red mixed with red would simply create more red, he was disappointed to nd this was not the case and his red lake turned out extremely pale. He attempted to concentrate it, whereupon it turned purple before becoming deep blue.

The animal blood had spurred an unlikely chemical reaction, which created the compound iron ferro- cyanide, now known as Prussian Blue.

The pigment was available to artists by 1724 and was immediately popular. Costing just a tenth of the price of Genuine Ultramarine, Prussian Blue was a very attractive alternative and its introduction saw the demise of Azurite, another mineral blue, from the artists’ palette.

Outside of artistic application, it has also been used as a colourant is blueprint paper, as a laundry blue, aswell as in plastics, paper, and cosmetics.

There is even a pharmaceutical grade manufactured for ingestion to counter radiation poisoning.