This color contains the following pigments:
cadmium sulfide and cadmium selenide
CdS × CdSe
Cadmium Orange was the first true orange and was made by mixing Cadmium Yellow with Cadmium Red. It is a pure hue with excellent opacity and low toxicity compared with its predecessors. It also has very high hiding power. The greatest tinting strengths are possessed by the deeper shades. Only the highest grades contain pure Cadmium Orange without barium mixed in it. Cadmium pigments have been partially replaced by azo pigments, which are similar in lightfasness to the cadmium colors, cheaper, and non-toxic.
Cadmium Orange has excellent permanence, but like many cadmium pigments, it will fade in fresco or mural painting. The deeper varieties of this pigment are the most permanent. The paler varieties have been known to fade when exposed to sunlight.
Cadmium Orange is a known human carcinogen. It is extremely toxic if inhaled and slightly toxic if ingested.
Cadmiums get their names from the Latin word cadmia, meaning zinc ore calamine, and the Greek word kadmeia, meaning Cadmean earth, first found near Thebes, the city founded by the Phoenician prince Cadmus. Metallic cadmium was discovered in 1817 by Friedrich Strohmeyer. It was used sparingly after its discovery due to the scarcity of cadmium metal.
Zinc White is the coolest white, and it has a cold, clean masstone and a slightly bluish tint. It has less hiding power and is more transparent than other whites. It dries slowly and is good for painting wet into wet and for glazing and scumbling. Zinc White is neither as opaque nor as heavy as Lead White, its covering power is not as good, and it takes much longer to dry. However, it does not blacken when exposed to sulfur in the air as Lead White does. It is very valuable for making tints with other colors. Unmixed Zinc White dries to a brittle and dry paint film that may crack over the years, so it is not good for frescoing. It is more transparent in acrylic form than Titanium White and is the most commonly used white with gouache. Chinese White is a version of Zinc White appropriate for opaque watercolor techniques.
Zinc White has great permanence and lightfastness.
Zinc White is moderately toxic if ingested and slightly toxic if inhaled.
Though historians are divided on who first isolated the element zinc, they agree that it was first suggested as a white pigment in 1782. Zinc White was accepted as a watercolor in 1834 and was called Chinese White due to the popularity of oriental porcelain in Europe at the time. Ten years later, a suitable oil form was produced. By the early 20th century, it had improved to the point where it was an acceptable alternative to Flake White.