Winsor & Newton Professional Watercolor - Terre Verte, 14 ml Tube

Pigment Information

This color contains the following pigments:

PG23-Green Earth

PB28-Cobalt Blue

PG18-Viridian

Pigment Name

PG23-Green Earth

Pigment Type

earth

Chemical Name

hydrated iron, magnesium, aluminum and potassium silicates

Chemical Formula

K[(Al,FeIII),(FeII,Mg)](AlSi3,Si4)O10(OH)2

Properties

Green earth is a natural pigment that varies from yellow and olive to blue-green in its composition and hues. It is semi-transparent, has low hiding power and tinting strength, muddies and darkens in oil, and is particularly good for tempera and fresco painting.

Permanence

Green Earth has excellent permanence and lightfastness, although some varieties can be developed by light calcining. It is one of the most permanent pigments because Earths are not affected by sunlight or atmospheric conditions.

Toxicity

Green Earth has no significant hazards.

History

Terre verte is French for green earth. It was discovered in antiquity, and its use has been traced to the Ajanta caves in India and a variety of Roman sites, including Pompeii. Green Earth was very popular for underpainting flesh tones in medieval paintings because this green was the compliment to pink on the medieval color wheel. Its use declined after the Renaissance. The natural supplies of the pigment are mostly depleted, and manufacturers currently duplicate the hue using mineral bases like Viridian, iron oxide, or chromium oxide, or artificial ceramic colorants. Pigments sold under this name can also be the result of mixing Sienna and Phthalo Green.

Pigment Name

PB28-Cobalt Blue

Pigment Type

inorganic

Chemical Name

cobalt(II) oxide + aluminum oxide

Chemical Formula

CoO + Al2O3

Properties

Cobalt blue is a semitransparent pigment with low to moderate tinting strength. When it dries, it appears lighter and less saturated. Pigment particles are large and grainy. Differences in how the pigment is ground and mixed lead to considerable differences in its performance among various manufacturers.

Permanence

Cobalt blue is absolutely lightfast and extraordinarily stable. The stability of cobalt salts at high temperatures make them the standard for blues used in ceramics and glassware.

Toxicity

Cobalt salts are toxic. Avoid respiratory and skin contact. Soluble cobalt may cause irritation and allergic reaction through contact with skin. It is considered a possible carcinogen.

History

Since ancient times, smalt blue has been used to color glass and ceramics. Cobalt salts, which give smalt its characteristic blue color, were identified in the 18th century. Techniques for manufacturing Cobalt Blue, a chemically pure salt of cobalt and aluminum oxide, were developed in 1802.

Pigment Name

PG18-Viridian

Pigment Type

inorganic

Chemical Name

chromium(III)-oxide dehydrate

Chemical Formula

Cr2O3 • 2 H2O or Cr2(OH3)

Properties

Viridian is the standard green and is stable, powerful, and cold with an emerald green undertone. It has a transparent hue, good tinting strength, a dark masstone that can be almost black at full strength, and a slow drying time in oil form. Viridian is commonly replaced by the darker, more saturated, and staining Phthalo Greens, but its properties make it a necessary part of the palette of an experienced landscape painter.

Permanence

Viridian has excellent permanence, except in high-temperature work, and is highly valued as a glazing color.

Toxicity

Viridian is slightly toxic.

History

Viridian’s name comes from the Latin viridis, meaning green. The process for manufacturing Viridian, or Transparent Oxide of Chromium, was patented by Guignet in Paris in 1859. However, it had actually been discovered by Pannetier and Binet in 1838. Viridian replaced Verdigris, which was reactive and unstable, and Emerald Green, which was a poisonous copper aceto-arsenite used as a rat poison in the sewers of Paris.