Iron blue, besides being one of the earliest, is still one of the most widely used and cost-effective blue pigments.
The name iron blue is the modern and more definitive description of a range of ferrocyanide pigments known historically, by a variety of other names including: Prussian blue, Chinese blue, Bronze blue, Milori blue, Paris blue, Non bronze blue and Engineers blue.
Iron blue was first mentioned in 1710 in a Latin text written by an unknown author and its properties were described in a reference from 1726. It is said to have been discovered by the chemist and painter DIESBACH in 1704, but other sources mention the chemist Johann Conrad DIPPEL, for whom DIESBACH worked.
The first mention of its manufacture was by the English chemist WOODWARD in 1726. Potash and ox blood were heated until they glowed and then subsequently boiled for one-half hour with rainwater. The “blood lye” obtained in this way was heated together with a sulfate and alum. This produced a green intermediate product, also called “mountain green” or “crysocollage green”. The material was then washed and filtered. After a treatment with hydrochloric acid, the product eventually turned to a deep blue color.
Iron blue only became significant from an industrial and economic viewpoint however, at the end of the 18th century. The Frenchman MILORI was the first to manufacture iron blue on a commercial scale.