Colour story: Prussian Blue

Deep, bold and intense, Prussian Blue is the first synthetic blue pigment to have ever been made. Discovered completely by chance, it quickly became popular as an exciting and much cheaper alternative to the only permanent blue pigment available at the time, Ultramarine. Used by artists like Watteau, Hokusai and Picasso, Prussian Blue has revolutionised the artist’s palette, ever since its happenstance invention.   

It was by accident that Johann Jacob Diesmach invented Prussian Blue in 1704. The Berlin-based colourmaker had been attempting to create a red lake pigment to use as a dye. To do this, he was using iron sulphate and potash, and on this lucky occasion, the potash was contaminated with impurities in the form of animal oil.  

Instead of a bright red, it produced a purple. And when concentrated, it became a deep blue pigment. Mined in limited amounts in Afghanistan, deep-blue Ultramarine (lapiz lazuli) was extortionately expensive and often scarce. This accidental discovery therefore provided a new alternative to the highly prized colour, altering the canon of painting pigments for good. 

By 1710, Prussian Blue was being used by many artists in the powerful Kingdom of Prussia that ruled much of northeastern Europe, giving it its name. Use of the pigment continued to spread through other European regions. Watercolour and oil colour works painted by artists such as Antoine Watteau and Jean-Baptiste Pater revealed that they had taken up using Prussian Blue.  

The pigment began to travel across the globe. It famously made its way as to Japan, where it was used by woodblock artists such as Katsushika Hokusai in his iconic 1831 painting The Great Wave off Kanagawa. Since then, Prussian Blue has featured in the palettes of artists including Monet, Constable, Gainsborough, Lowry and Picasso – particularly throughout the latter’s ‘Blue Period’. 

Many of these historic paintings reveal that Prussian Blue has a tendency to become greyish and fade over time. Winsor & Newton decided to launch Winsor Blue in 1938, as a stable and lightfast version to replace the Prussian Blue pigment of the era. Winsor Blue comes from the phthalocyanine family of colours, which were first chemically synthesised in the late 1920s. Many new synthetic organic pigments were being discovered around this time, but only three were universally accepted for their artist-grade quality in the 1950s: phthalocyanine blue, phthalocyanine green and alizarin crimson. 

Today, Winsor & Newton’s Prussian Blue is a beloved intense blue pigment. With a high tinting strength, Prussian Blue produces a range of hues, from the palest tint to a deep blackish-blue.