Alchemists, Prussians and Napoleon’s Egyptian Campaign: How New Shades of Blue were Discovered in the 18th Century

The 18th century saw an increase in scientific knowledge and practical research. Many findings found their way into everyday life, craft and commerce. New technics allowed, e.g., to create new colours. Find out here what Napoleon’s Campaign in Egypt, the Prussians and an apothecary had to do with the various blue pigments created in the long 18th century.

1706 Prussian Blue

Legend has it that Johann Jacob Diesbach, working as a paint manufacturer in Berlin / Prussia, discovered a new shade of blue by accident: he had been in the process of making a red colour from crushed cochineal insects, iron sulphate and potash, when one batch of the product did not turn red at all, but from pale pink to purple and finally to a deep blue. He contacted the supplier of the potash, a certain Johann Konrad Dippel, theologian, physician and alchemist. Together, they found out that the unexpected reaction had occurred because the potash sold by Johann Dippel had been contaminated with bone oil (which was supposed to be the equivalent to the alchemists’ dream of the ‘elixir of life’, but mainly was a nitrogenous by-product of the destructive distillation of bones).
The new blue came in use quickly: from the beginning of the 18th century, Prussian blue was the predominant uniform coat colour worn by the infantry and artillery regiments of the Prussian Army.
The dark blue pigment Prussian blue (also known as Berlin blue) was the first modern synthetic pigment, and the first stable and relatively lightfast blue pigment to be widely used. It replaced the expensive blue colour made from Lapis Lazuli.

1789 Cerulean Blue

For many centuries, paint manufacturers had attempted to create sky blue colours. The results had been unsatisfactory: the pigments had a limited saturation and tended to discolour in reaction with other pigments. Finally, in 1789, Swiss apothecary Albrecht Höpfner succeeded! He invented a blue pigment, opaque and bright due to its highly refractive particles, which did not react to light or chemicals. Höpfner called the new blue ‘coelinblau’ (cerulean, sky-blue). To make the colour, he used English tin, aqua regia and erythrite. His first production line of coelinblau was limited and short-lived, as Höpfner went bankrupt. He kept experimenting privately, and created cerulean blue from cobalt stannate in 1805, profiting from the work of Louis Jacques Thénard (see below). However, the colour did not become widely available to artists until the 1860ies.

Being an apothecary, Höpfner strongly believed in professional ethics. He thus published his recipe for cerulean blue in a periodical he ran, so that everyone could give a try at making the pigment.

Find here the original recipe from 1789 to make cerulean blue :

Dissolve 3 lots (one lot is 1 1⁄32 of a pound) of roasted erythrite in aqua regia from one side. Dissolve 6 lots or more (depending how light or dark the colour should become) of pure English tin (lead-free) in aqua regia by the known method. Mix the two together – filter them before – and stir in a solution of pure potassium hydrogen tartrate, until saturated. Heat the mixture and recausticise it. When recausticised and dried, put it in a flat porcelain pot, such as a saucer, and place it under a muffle, after having spread the precipitate in the saucer. Add heat, and more heat, until a blue colour is achieved. Experiments conducted with erythrite from the mine „Guete Gottes“ in the area of Fuerstenberg always were successful.
(Albrecht Höpfner, 1789)

The original recipe to make the pigment ‘Cerulean blue’

1798 Egyptian Blue

Egyptian blue was rediscovered and brought into fashion by the Egyptian Campaign of Napoleon, when the scientists of the campaign explored ancient sites and brought home artifacts, some of them glazed or painted with a light blue colour. The results of the scientific research were published in the book “Voyage dans la basse et la haute Egypte (Journey in Lower and Upper Egypt)”, written by Vivant Denon and published in 1802. Egypt inspired everything from sofas with Sphinxes for legs or turban for lady’s evening fashion, to tea sets painted with the pyramids. Naturally, the discoveries triggered numerous subsequent researches.

Egyptian figurines coloured in Egyptian blue (collected by gentleman Egyptologist William Bankes around 1815 – 1819 / on display at Kingston Lacy / UK

Additionally, 1814, a group of scientists that included the British chemist Humphry Davy unearthed a pot of an unknown “pale blue colour” at Pompeii. Davy was particularly interested in the chemistry of ancient pigments. He collected pigments in both Pompeii and Herculaeum. He realised that he had rediscovered the material ‘of which the manufacture is said to have been anciently established at Alexandria’. It was concluded that Egyptian blue was a synthetic pigment used in the early dynasties in Egypt until the end of the Roman period in Europe. It then became forgotten. Davy’s researches were interrupted by Napoleon’s escape from Elba and his march towards Paris. He returned to London, as Europe prepared for war again.
Today we know that Egyptian blue can be synthesised by heating a raw material mixture consisting of quartz sand, limestone, copper ore and a flux (soda or plant ash) to about 950°C.

A discovery at Pompeii, reported by Humphry Davy:

Among some rubbish collected in one of the chambers of the baths of Titus were several large lumps of a deep blue frit, which, upon being analysed, were found to consist of soda, silica, and oxide of copper. Upon examination of the different tints of blue observable in the paintings of the baths, as well as several blues in fragments of fresco painting from the ruins near the monument of Caius Cestius, and from excavations made at Pompeii, it appeared that they all consisted of the same blue frit, more or less diluted by admixture with carbonate of lime. There appears to the author every reason to believe this to be the colour described by Theophrastus, as disco­vered by an Egyptian king, and anciently manufactured at Alexan­dria. Vitruvius also speaks of the same colour under the name of caeruleum, made in his time at Puzzuoli, by heating together sand, flores nitri or natron, and filings of copper.
(Humphry Davy, 1815)

1799 Cobalt Blue

The invention of Cobalt blue is credited to the French chemist Louis Jacques Thénard in 1799.
The French Minister of the Interior had ordered Thénard to create an inexpensive blue as beautiful as Lapis Lazuli for the Sèvres Porcelain Manufacture, as the pigment had become scarce due to the war. Thénard was given 1,500 francs, and he went to work (not very happy with the task, as he had other pressing projects at hand). He soon came up with a pigment he made by sintering cobalt(II) oxide with aluminum(III) oxide at 1200 °C. In 1804, after experimenting with various cobalt compounds, Thénard obtained a highly stable pigment with a deep and intense blue that could be made at lower cost. Commercial production began in France around 1807.
Cobalt blue quickly became the favourite blue of artists, including the English painter J.M.W. Turner. It is believed that the earliest recorded use of Cobalt blue in art is in the sky of J.M.W. Turner’s oil sketch of “Goring Mill and Church“. Another early adopter was Caspar David Friedrich who used Cobalt blue in the sky for his painting “Riesengebirgs Landscape with Rising Fog“. Turner continued to use Cobalt blue in many of his paintings, such as “Ulysses Deriding Polyphemus” and “Fighting Temeraire“.

JMW Turner used Cobalt blue to great effect for his painting “Fighting Temeraire” (photo taken at The National Gallery, London)

Cobalt blue in ‘impure’ forms had been used in the past, e.g., for Chinese porcelain. In the second half of the 18th century, artists and craftsmen had worked with other impure forms of cobalt blue: The first synthesis of a cobalt blue pigment (named ‘Leithners Blau’) is attributed to porcelain painter Josef Leithner, who used a cobalt aluminosulphate at a Vienna Porcelain Manufactory. However, his blue pigment was never industrially produced. In the 1770ies, a blue created from aluminium salts mixed with a cobalt solution was used at a Saxony Porcelain Factory. The process of creating the colour was considered a trade secret. In England, the first recorded use of cobalt blue as a colour name was in 1777.
Thénard discovered the pigment cobalt blue independently from its forerunners as a pure alumina-based pigment. His Cobalt blue, established in the nineteenth century, was a greatly improved one.

Egyptian figurines coloured in Egyptian blue (collected by gentleman Egyptologist William Bankes around 1815 – 1819 / on display at Kingston Lacy / UK

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Article by Anna M. Thane, author of the novel
“Von tadellosem Ruf” (