Prussian Blue took the art world by storm when it was first synthesized in 1706. This iridescent shade of dark blue would go on to feature in many of the greatest artworks of the next 200 years, including Hokusai’s Great Wave and van Gogh’s The Starry Night – both of which owe their enduring luminosity to the pigment’s refusal to fade. It is gloriously poetic, then, that the story of Prussian Blue, in all its radiant glory, is tied to some of the darkest moments in human history.
Prussian Blue comprises iron cations, cyanide anions, and water. It is therefore bound by blue blood to one of the most famous poisons of the modern era, cyanide. In liquid form, this light blue poison burns at 26 degrees Celsius, at which point it begins to release the aroma of almonds. Around 60 per cent of the global population have the gene necessary to pick up this particular characteristic, meaning that the Jewish prisoners murdered in Auschwitz and Treblinka may have died with the smell of Marzipan swilling around their nostrils. An early form of the airborne poison, Zyklon B, was used as a pesticide in the Orange farms of California in the 1930s. At that time, it was also used to delouse the trains where thousands of Mexican immigrants hid during their crossing into the US. After being sprayed countless times, those train cars became stained a brilliant blue, the same shade that covers the inner bricks of the gas chambers at Auschwitz.
When the Swiss pigmenter Johann Jacob Diesbach accidentally discovered Prussian Blue while attempting to make a batch of Florentine Lake – a red pigment made of crushed red insects – he believed he had created hsyd-iryt, the colour used by the Ancient Egyptians to colour the skin of their gods. It was, in ancient times, believed to be the original colour of the sky and was so revered that the recipe was guarded by Egyptian priests and passed down in secret. Diesbach named the pigment Prussian Blue in honour of the Prussian Empire, whose military used it as a dye in their soldier’s uniforms.
The relative expense of Prussian Blue meant that it quickly replaced Ultramarine, which the painters of the Renaissance had once used to colour the robes of their angels. The first great master to use Diesbach’s Prussian Blue was the Dutch painter Pieter van der Werff, who in 1709 used the pigment in his portrayal of The Entombment of Christ, allowing the blue mask that cloaks the Virgin Mary’s tear-dappled face to shimmer with heavenly lustre. Over the next couple of centuries, Prussian Blue became one of the most sought after ingredients in the art world, appearing in works by Gainsborough (Mrs Siddons, 1785), Sir Joshua Reynolds, Delacroix (Pieta, 1850), and JMW Turner (The Fighting Temeraire, 1838). This dazzling indigo would also give the swirling sky in van Gogh’s The Starry Night its infinite depth and radiance, while also allowing the water in Hokusai’s famous Woodblock, The Great Wave, to take on the tranquil fury of a living sea.
All of this artistic brilliance is underpinned by a strain of violence, and not simply because of the pigment’s relationship to cyanide. The popularity of Prussian Blue wouldn’t have even been possible without the help of Johann Dippel, the Berlinese alchemist whose studio served as the setting for Diesbach’s startling discovery. While widely regarded as a quack, Dippel was determined to become the first man to successfully transplant the soul of a living being into a dead body. This irrepressible ambition led him to engage in all manner of brutal experiments, the majority of which involved him dissecting living birds and other animals in a state of sickening euphoria. Indeed, it was Dippel’s taste for stitching animals together to create vile chimaeras that led Mary Shelley to use him as the model for the titular scientist in her 1818 novel, Frankenstein.
The life of Prussian Blue is so eye-wateringly colourful that it’s impossible to capture in a mere 500 words or so. If you are interested in finding out more about the subject, I’d recommend grabbing a copy of Benjamin Labatut’s When We Cease To Understand The World, the first story of which offers a wonderful insight into its astounding cultural significance.