In 1704 the dye-maker Johann Jacob DiesbachIt made a chance discovery that characterises so much of the history of artists’ colours and in the process invented the first modern, artificially manufactured colour.
Working in his Berlin laboratory on a cochineal red pigment, he disregarded the fact that one of his raw materials, potash, had been contaminated with animal blood. In the belief that red mixed with red would simply create more red, he was disappointed to find this was not the case and his red lake turned out extremely pale. He attempted to concentrate it, whereupon it turned purple before becoming deep blue.
The animal blood had spurred an unlikely chemical reaction, which created the compound iron ferro- cyanide, now known as Prussian Blue.
The pigment was available to artists by 1724 and was immediately popular. Costing just a tenth of the price of Genuine Ultramarine.
Crocoite, a bright red crystal was discovered in Siberia in the 18th century. When crushed it produced a deep orange powder.
In 1797 chemists realized this was a new element initially called chrome (from the Greek for ‘colour’). Soon after, the possibilities for its use in pigment manufacture were recognized and the first methods of preparation were invented. It could be made into a range of strong bright pigments from yellow through to rich orange and even red.
It was a relatively cheap pigment to manufacture with high covering power but however the pigment tends to darken on exposure to air over time. The chrome colours were in use by 1816 and were used by, amongst others, Van Gogh where the effects of its discolouration are now highly evident.
Where would our understanding of late 19th century art be without the invention of the cadmium colours?
The Impressionists devoured this range of previously unseen bright opaque primaries to build their vibrant, colour-charged immediate interpretations of the world around them.
Cadmium Yellow is formulated from cadmium sulfide. Discovered in 1817, production of the cadmium yellow pigments was delayed until about 1820 because of the scarcity of the metal ore.
They can be made into various shades ranging from a lemon yellow through to deep orange depending on the size of the pigment grains in the manufacture process. The deeper hues are known to have better lightfastness.
In German folk legend Kobald was the name of a vicious sprite, who lived in the earth to haunt the mines and torment the miners.
Cobalt occurs naturally in the ore smaltite (a mixture of cobalt and nickel arsenides). When exposed to air, this forms a brilliant blue brous crystal known to miners as ‘cobalt bloom’. It is a dangerous flower, for the arsenic compounds in the mineral dust are toxic.
The use of cobalt as colouring material in pigments such as smalt had been known at least since the Middle Ages, but the purer cobalt colours created in the 19th century were far more intense and stable.
In 1802 Thénard synthesized a blue solid by mixing cobalt salts with alumina. Thénard’s blue (cobalt aluminate) had a purer tint than azurite, Prussian blue or indigo, and was taken up immediately as a pigment. It was expensive but popular none the less, its only serious competition came from the synthetic version of ultramarine.
Yet there was more to be had from the chameleon-like qualities of cobalt:
In the mid-19th century, three more cobalt colours appeared on the market: green, violet and yellow.
Cobalt green had a composition similar to cobalt blue but with some or all of the alumina replaced with zinc oxide. It had been originally discovered before cobalt blue in 1780. However, only when zinc oxide became readily available was the manufacture of cobalt green viable. It does not have particularly good opacity and like all cobalt pigments, it remained expensive.
Cobalt Violet was manufactured in France from 1859 but, not unlike its older sister Cobalt Green, its high cost and low tinting power limited its use among painters.
The most complex of the cobalt colours was a yellow that painters knew as Aureolin. First synthesized in 1831 it was not sold as a pigment until its independent rediscovery in the early 1850s and released onto the market in 1861.
By the 19th century Genuine Ultramarine had become so expensive that artists could rarely afford to use it.
In 1824, the Societé d’Encouragement offered a prize of six thousand francs to anyone who could produce a synthetic replacement not to exceed three hundred francs per kilo and less than a tenth of the cost of genuine ultramarine.
It had been noticed in the previous century that blue deposits collected on the walls of lime kilns. The glassy blue was cut off and used locally as a substitute for lapis in decorative work. From these observations chemists began their investigations
In 1828, Jean Baptiste Guimet perfected a method of producing arti cial ultramarine made by heating a mix- ture of China clay, soda ash, coal, charcoal, silica and sulfur.
Because its invention was requested of chemists by the French government it became known as French Ultra- marine to differentiate it from the natural product.
The terms Ultramarine and French Ultramarine are now used by paintmakers to describe different blue hues, the naming is an echo of a time when the natural and arti cial were still sold together.
As well as the more famous blue, ultramarine can be carefully manufactured into redder shades by further processing.
Ultramarine Violet is made by heating a mixture of ultramarine blue and ammonium chloride. Ultramarine Pink is derived from ultramarine violet by heating it with gaseous hydrochloric acid.
As the ultramarines move towards the red shades they lose their tinting strength and opacity.
The ultramarines are permanent, non-toxic and cheap to produce and used in an incredibly wide range of industrial applications.
Chromium Oxide Green
Like cobalt, chromium is a chameleon metal.
The method of its manufacture was patented in 1859.
Chromium Oxide Green, also known as chromium sesquioxide is one of four oxides of chromium.
It is a rather leaden opaque green more in the direction of olive green. Its value is in its good tinting strength, high stability and tonal equivalence to the iron oxides.
Chromium oxide’s more vibrant cousin is known as Viridian. In French it is called vert émeraude (Emerald Green), not be confused with the highly poisonous copper-acetoarsenite Schweinfurt green (also called emerald green) which was used until the early 1900’s.
Viridian soon replaced Emerald Green, particularly in industrial printing processes and quickly became a popular artists’ pigment due to its excellent perma- nence and lack of toxicity.
A cold transparent green with limited tinting strength it is still popular for glazing although superseded by Phthalocyanine Green in the second half of the 20th century.
Invented in 1868, Manganese Violet has had an illustrious modern history. Relatively cheap to produce, a powerful, lightfast colour formulated as ammonium manganese(III) pyrophosphate it quickly replaced the weaker Cobalt Violet pigment.
The Impressionists, especially Monet, so adored the new hue that critics accused the painters of having “violettomania.”.
First discovered in 1907 but not patented until 1935 Manganese Blue is a clear azure blue and was initially produced to colour cement (mainly for swimming pools) as well as an artists’ pigment.
Manganese blue was prepared by mixing barium manganate on a barium sulfate base.
A relatively weak tinting pigment, especially in oil, it never became a major pigment for artists and its production was discontinued in the 1990’s due to environmental concerns and toxicity.