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.