Dark brown pigment. It is a carbonaceous, humic or bituminous substance impregnated with iron hydroxides. Kassel and the closely related "Cologne earth" were widely used in painting in the 16th - 17th centuries. These pigments received their name from the place of their extraction.

The pigment consists of 33 - 60% organic substances. The iron hydroxide content is usually 8 - 25%. In addition, it usually contains: montmorillonite (up to 20%), quartz (about 5%), pyrite (1 - 6%), carbonates (2 - 4%), and bound water (10 - 16%). Usually, Kassel earth deposits are found among brown coals.

The pigment "brown Van Dyck" (the spelling varies) close to Kassel earth is distinguished by lower iron oxide content. In Russia, this pigment is known as "van dyck". The pigment has a beautiful brown-black color, glazes in oil paint. When heated above 150 ° C, it changes properties

•Chemical description: natural carbonaceous earth impregnated with iron hydroxides.

Composition: Quartz 35.3%, Goethite 26.8%, plagioclase (anorthite) 3.3: organic carbon 34.5%

•Lightfastness - 7

•Alkali resistance: 5

•Lime resistance: 5

•Acid resistance: 5

•ColorIndex NBr8

•Glazing

•Suitability Acrylic, Fresco, Ceramics, Oil, Tempera, Watercolor / Gouache, Cement / Plaster

•Color dark brown

•Form powder