This pigment is a high-quality, clean, medium-shade, stable green pigment unaffected by acids, alkalis, and solvents. It is heat stable and offers excellent value, lightfastness, and weatherability.

The element chromium was found in lead chromate in 1797 by Louis-Nicolas Vauquelin. The element was named chromium because so many colored compounds can be produced from it. As early as 1809, chromium oxide was used as an enamel in porcelain factories but was not yet used as a painting pigment. Several sources have written that chromium oxide was not used as a pigment until 1862, but evidence suggests it was used earlier. The pigment has been identified on a J.M.W. Turner painting, which dates back to 1812. An 1815 journal entry by George Field included a homemade example of the pigment. In 1831, Vergnaud discussed two different preparation methods but said that the pigment was not widely used because of its high price. A catalog of pigments printed around 1840 lists a green oxide of chromium believed to be chromium oxide. Also, in 1969, Kühn found chromium oxide in three paintings dated between 1845 and 1850 using microscopy and emission spectroscopy. It is widely accepted that chromium oxide was used before the hydrated version. However, their use has been limited since these greens are much more expensive than emerald greens or chrome greens due to the preparation process. It is sometimes used to make lightfast paints when mixed with yellows. In the past, it was used in automotive finishes and to make bank notes.

The first man to prepare chromium oxide was Pannetier in Paris, but his process was kept hidden. Guignet invented a two-step process for preparing the chemical. His first step was to heat boric acid and potassium bichromate, a process known as calcining, which produced a porous mass. The second step produces hydrated oxide, boric acid, and some boron after the mass is washed in cold water or hydrolyzed. This is only one of several ways to prepare chromium oxide. Hydrated chromium oxide has no specific chemical composition since different preparation processes produce the chemical with boron, while other processes produce the chemical without boron.

Hydrated chromium oxide is permanent, but chromium oxide is more stable and is one of the most permanent pigments an artist uses. It will not react with hydrochloric acid or sodium hydroxide, so it is safe in alkali and acid environments, making it suitable for fresco and outdoors.

Chromium oxide green absorbs a small amount of oil (26 grams per 100 grams of pigment).

Though chromium oxide green is not a severe health hazard, it can irritate the skin and eyes and cause nausea and other problems if ingested. Dust inhaled can also cause respiratory problems. It is not a fire hazard and does not readily react with other materials. This pigment is FDA-approved (Section 178.3297). It can be used in polymers used in contact with food at a level not to exceed 5% of the weight of the polymer. In olefin polymers, it complies with 177.1520 of this chapter. The pigment in repeat-use rubber articles complies with 177.2600 of this chapter, and total use is not to exceed 10% by the weight of rubber articles.

Pigment: Chromium Oxide Green