Sennelier Oil Pastel - Earth Brown

Pigment Information

This color contains the following pigments:

PB28-Cobalt Blue

PW7-Zinc Sulphide White

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

PW7-Zinc Sulphide White

Pigment Type

inorganic

Chemical Name

zinc sulfide

Chemical Formula

ZnS

Properties

Zinc Sulphide White is a semi-transparent yellowish white pigment. Zinc sulfide and zinc oxide (PW4) are often combined to create a more natural white color. Transparency increases as particle size decreases. When slight impurities are added, zinc sulphide has phospherescent and electroluminescent properties. It is often used to manufacture fluorescent or glow-in-the-dark paints.

Permanence

Zinc Sulphide White has excellent permanence and lightfastness.

Toxicity

Zinc Sulphide is non-toxic, but ore deposits often contain lead. Traces of lead and other impurities may be present in pigment powders. Ingestion is not recommended.

History

Zinc sulfide, when combined with slight impurites, has phospherescent properties. It is often used for "invisible ink" that glows with exposure to ultraviolet light. Zinc sulfide is used in the manufacture of fluorescent paints.