Viridian

Here's an information sheet on my second researched pigment. I'd somehow come to the conclusion that Viridian was something of an earth pigment. Not nearly so! It's a synthetic first created well over a hundred years later than Prussian Blue.

Viridian, a transparent bluish green, is closely related to Chromium Oxide, an opaque warm green.

Common Name: Viridian

Alternate Names: Guignet's Green

Color Index: PG 18 77289

Composition: Cr₂O₃ · 2 H₂O, a hydrated chromium(III) oxide

Specific Gravity: 3.5

Refractive Index: 1.62, 2.12

Particle Size: 5 microns

Synthetic Inorganic

Lightfastness: very good.

Excellent tinting strength and stability in all mediums. Unaffected by dilute alkalis and acids. Unaffected by light.

Moderately toxic. Though chromium oxide green is not a serious health hazard, it can cause irritation of the skin and eyes, and can cause nausea and other problems if ingested. It also can cause respiratory problems when dust is inhaled. It is not a fire hazard, and does not readily react with other materials.

A permanent green pigment composed of hydrated chromium oxide. Viridian is a synthetic pigment with characteristic deep green, transparent particles which are unaffected by light and chemicals. The process for making the hydrated form of chromium oxide was discovered in 1838 by Pannetier in Paris. A less expensive method for manufacturing viridian was patented by Guignet in 1859. Viridian, though not extremely popular because of its high price, was used as a pigment in all types of binding media. The stable pigment is also used as a colorant in concrete mixtures, rubber, inks, and automotive paints.

Kremer (44250) $25.00/100g  Transparent chromium oxide

Timeline:

• 1838 First made by the color maker Pannetier in Paris. Binet took over when Pannetier died. Worked in secret.
• 1859 Guignet patented a method. The new green replaced Schweinfurt green for printing and other industrial coloring purposes.
• 1862 Introduced in Winsor and Newton.