Rublev Colours black oxide is a dense, opaque, heavy color that is absolutely permanent. It is comparatively cool to neutral in undertone, wets easily, and is non-greasy, when compared to carbon blacks. It is a useful pigment when these qualities are required.Origin and History
Black oxide is a recent development in modern pigments and was unknown in artists' palettes before the nineteenth century.Source
The source of black oxide usually is from an iron ore called magnetite. Magnetite, also known as lodestone, is a ferrous ferric oxide (ferrosic oxide) that is a heavy, black color and opaque. Theoretically, black iron oxide contains slightly more iron metal than red oxide but not nearly as much as yellow oxide. The native mineral may contain varying amounts of manganese, sulfur, clay and silica.Permanence and Compatibility
Black oxide is absolutely permanent colors for all uses on the artist's palette. It is compatible with all other pigments, and can be used with good results in all mediums.Oil Absorption and Grinding
Black oxide absorbs a moderately low amount of oil. The oil absorption ratio is 10–15 parts by weight of linseed oil to 100 parts by weight of pigment. If the measurement were grams, it would require 100 grams (by weight) of pigment to grind 10 to 15 grams (by weight) of linseed oil to form a stiff paste. It makes an average drying oil paint, and forms a hard, fairly flexible film.Toxicity
Black oxide is not considered toxic, but care should be used in handling the dry powder pigment to avoid inhaling the dust.
Rublev Colours Pigment: Black Oxide