How to Grab Yellow Pigments: Desire for Sun, Cadmium and Gold

Pierre la Mure describes how the young Henri de Toulouse-Lautrec was learning to paint and that every time he wanted to add a little yellow to the canvas, he had to go to a teacher who would give him a little bit of paint from a tube. At the price was realistic painting modeled after Rembrandt where earthy and muted tones prevail, shadow painting. But – Rembrandt’s genius is one thing, and the fact that a series of painters imitated his style and color is another. A little color needed to be added to the world.

And then, when they grew up, when they were not accepted into the famous Salon, that generation of impressionists and post-impressionists who were oppressed by muted tones will launch colors and will use them reluctantly. Some, like Vincent van Gogh, will apply paint directly from the tube to the canvas, which was really wasteful and a carnival of colors. In part, a small chemical revolution in the synthesis of pigments contributed to this, so colors became somewhat more accessible. In the second part, the scattering of colors, the explosions on the painter’s canvas were a rebellion, a response to the practical censorship of colors.

 

Yellow and orange are not as rare in nature as blue. It is found in plants in the form of xanthophyll and carotene pigments – they are found in fruits, roots, and flowers. However, the problem with these organic yellows and oranges is that they oxidize over time, losing their brightness and luster. That is why mineral pigments are used in art, which are more stable, but also rarer. And, while for orange-red and brown tones the choice is quite wide – different iron oxides in one or another ratio quite satisfy the need for these colors, until then bright, sunny yellows and healthy, bright oranges are quite a problem.

This is where we need cadmium compounds – cadmium sulfides or cadmium selenides. Cadmium was discovered by Friedrich Stromeyer in 1817 as an impurity of zinc carbonate. It was also discovered by Karl Hermann in the same year.

Although it was discovered in 1817, the production of cadmium pigments was delayed until around 1840 due to a shortage of the metal. A natural mineral, green ochite, is known in nature, but has not been used for pigments. Cadmium sulfide was produced with an acidic solution of a cadmium salt (either chloride or sulfate) that was heated with hydrogen sulfide gas until a powder was formed. Shades ranging from lemon yellow to dark orange were created in this way.

Deeper shades of cadmium yellow and orange were the most durable. Light shades of this pigment are known to fade under the influence of sunlight. All cadmium pigments are glossy, and the deeper shades have the greatest tinting power. From the middle of the 19th century, yellow cadmium pigments came into use in painting, but only at the turn of the century, in the era of impressionism and especially post-impressionism and expressionism – yellow flourished and artists used it abundantly. Gustav Klimt stands out from them, who during his “golden phase” used real gold leaf for some of his most famous portraits of women.

Before the discovery of the synthesis of cadmium yellow pigments, auripigment was used as a yellow pigment , also known as “fool’s gold” because inexperienced gold seekers often mistook it for this precious metal. But, auripigment is not at all harmless – it is arsenic sulfide, which is poisonous, and its color is unstable.

Auripigment was the only yellow color available to artists until the 19th century, and it did not meet their needs. Until the appearance of cadmium pigments, and later chrome yellow and permanent organic pigments, artists tried to bypass yellow. And then imagine the joy when they finally got hold of it!

However, cadmium is not innocent either – it is a heavy metal that can get into water and soil, and some plants incorporate it well into their organism. For example, one such plant is tobacco.

The mining of cadmium – primarily because it is needed for batteries, and the mining of other metals, such as silver and lead, and only then of cadmium for its pigment, have led to the accumulation of cadmium in the rivers that flow through the areas of the cadmium mines.

In 1919, there was a poisoning in the Japanese prefecture of Toyama. In that area, people began to complain of pain in their bones and joints. The bones were softening and the kidneys were failing. The disease itself was called “itai-itai” which would mean “pain-pain disease”.

Increased demand for raw materials during the Russo-Japanese War and the First World War, as well as new mining technologies from Europe, increased mine production. Production increased even more before World War II. But from 1910 until 1945, cadmium was released in significant quantities by mining operations, and itai-itai disease first appeared around 1912.

Cadmium accumulates the most in the kidneys, and enters them by binding to metallothionein in the blood and traveling to the glomeruli in the kidney. After cadmium enters the tubules in the kidneys, it is released and accumulates in the renal cortex until it reaches toxic levels. When cadmium reaches dangerous levels in the renal cortex, it can deactivate metal-dependent enzymes or activate calmodulin, which plays a role in smooth muscle contraction via calcium levels.

After the kidneys experience extensive damage, people with poisoning begin to experience damage to the musculoskeletal system, due to disturbances in calcium homeostasis. This musculoskeletal damage is what causes the bone pain and bone deformities that characterize itai-itai disease.

But cadmium is useful, not only because it creates works of art, but also because it is used in the rods that control nuclear fission reactions in nuclear reactors because it absorbs neutrons.

For those who are traumatized by the story of toxins, here is finally something interesting about yellow art: German artist Wolfgang Laib paints with organic components – plant pollen. This is what one of his “Hazelnut Pollen” installations looks like at MoMa: