Alternate Names: Mars Yellow is the name given to the synthetic precipitated form of hydrated iron oxide. Color: Yellow Colour Index: Pigment Yellow 43 (42) (77492) ASTM Lightfastness: Oil: I Acrylic: I Watercolor: I
Ochre is a natural earth containing silica and clay tinted by hydrous forms of iron oxide, such as yellow-brown limonite or brown-yellow to green-yellow goethite, and traces of gypsum or manganese carbonate. Limonite is a general term used to describe all forms of hydrated iron oxide minerals (FeO(OH)) that occur as natural clay or earth. Limonite includes the minerals goethite, akaganeite and lepidocrocite. To be considered an ochre, the content of iron oxide must not be less than 12%. Depending upon the content of hydrated iron oxide, the color of ochre varies from light yellow to golden to orange. The higher the content of iron oxide in an ochre the greater its tinting strength and hiding power. Most yellow ochres are normally not calcined as heat does relatively little to alter their color. Like red iron oxides (hematite), they are found around the world and have been used as pigments since prehistory. French ochre, historically one of the best grades of limonite, contains about 20% iron oxide and is high in silica. In Russia, high quality ochres can be obtained from the Izyumskyy deposit in Ukraine, and the Zhuravskoye, Skarnovskoye and Dubovikovskoye deposits in the Voronezh region, and the Lyubytinskoye deposit near Novgorod.
Permanence and Compatibility: Ochre is among the most permanent colors among 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: Ochre absorbs a medium amount of oil. It slows the drying of oil paint, but forms an excellent film.
Toxicity: Ochre is not considered toxic, but care should be used in handling the dry powder pigment to avoid inhaling the dust.
Read cautions about handling pigments