Chrome-Yellow

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’). It is now known as chromium.

Soon after, the possibilities for its use in pigment manufacture were recognised and the first methods of preparation were invented. Lead chromate is made by mixing a solution of potassium chromate and lead-nitrate.

It could be made into a range of strong bright pigments from yellow through to rich orange and even red. The exact hue can be adjusted by co-precipitating it from solution with lead sulphate: the colour could also be varied by altering the temperature of the synthesis, which affects the size of the grains.

It was a relatively cheap pigment to manufacture with high covering power but with only fair lightfastness and chemical stability. 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.

Because it contains the heavy metal lead, it was quickly replaced by the cadmiums and by the early 1900’s had generally fallen out of artistic use.