Prussian Blue, along with alizarin crimson, is the pigment that’s reported light fastness and actual light fastness causes the most headaches in artists. But why is that? This article is the first of two on this pigment, inviting the reader to explore the history of the pigment, so that we can appreciate the historical context before diving into the chemistry as to why it is such a controversial colour.
Prior to its discovery, painters were severely limited in the choice of colours they had; lapis lazuli was so expensive that commissioners often had to buy the pigment for their own commissions, and indigo was notorious in it’s fading.
- Name: Prussian Blue
- Composition: Fe4iii[Feii(CN)6]3
- Colour Index: Pigment Blue 27
- Hue: Deep, cool (green-leaning) blue
Like most of the world’s greatest inventions, the discovery of Prussian Blue in 1706 was pure accident that came as a result blood tainting the attempts of Diesbach to make a red dye (Florentine Lake). The colour is widely considered the first of the modern synthetic pigments
For further information on the chemistry behind this, see my next article (I’ll do my best to make it not too intimidating!!)
Prussian Blue has gone by several other names, including (but not limited to) Berlin blue, Turnbull’s blue, Milori blue, Iron blue, or Paris blue. The wide variety of names is commonly attributed to the variance in hues that results from different synthesis methods and locations.
In chemical terms, the compound itself is known as iron (III) hexacyanoferrate(II). As you can deduce from the chemical name, one of the major constituents of Prussian Blue is cyanide. The poison, despite being colourless, actually gets its name from the Greek for ‘dark blue’, as a result of its presence in this compound! I should reassure you that Prussian Blue is not cyanogenic, and won’t release cyanide unless you literally go around burning it (please don’t!).
Prussian Blue is not only used as an artists pigment (although that is the dominant use). It is also used:
- As a treatment for heavy metal poisoning,
- As a stain to test for iron in tissue samples,
- As a laundry ‘bluing’ agent, to counteract the yellowing of clothes.
- In typewriter ribbons.
Prussian Blue was also the name of a crayola crayon for 55 years, before being renamed midnight blue in 1958.
The decline of Prussian Blue
Until the 1970s, Prussian Blue was one of the most prominently used blues, however the development of the brighter and substantially more lightfast phthalo blues caused a drop off in the use.
Artwork Using Prussian Blue
Famous works include; (select a few from pages 211-213).