Traditionally, ocher is called a yellow-brown color. Artistic paints in shades of ocher were widely used by Renaissance painters to paint their canvases. Such an attractive palette appeared in people thanks to the natural material of the same name.
Ocher and its varieties
Ocher is a family of naturally occurring earthy pigments that contain iron oxide as the main coloring component. Various types of ocher are mined from natural deposits of clay or sandy clay mineral. The dye is characterized by a variety of colors and shades, including yellow, dark orange, brown, red, violet.
Modern ocher pigments are often made using synthetic iron oxide.
The quality of natural ocher is influenced by various factors: the proportion of clay and iron oxide, the presence of coloring elements in the composition, and the conditions of the area. Yellow or gold ocher contains hydrated iron oxide, also known as limonite. In this substance, iron freely interacts with water. Partially hydrated iron oxide - goethite - gives the pigment a brown color.
In places where the soil is very dry, ocher will have a red color, which gives it anhydrous iron oxide - hematite. Violet ocher is close to red in its chemical properties, but its hue is determined by the diffraction of light caused by the large average particle size of the substance.
If a natural mineral heats up under the influence of temperature, it becomes thicker and denser. In this process, limonite or goethite is dehydrated and converted to hematite, and yellow or brown ocher becomes red.
Extraction and use of ocher
Archaeological research shows that long before our era, ocher was widely used as a dye, cosmetics, protection against drying out of the skin and from insects, as well as for religious purposes. In 1780, the French scientist Etienne Astier developed an industrial method for obtaining ocher, which was improved over time.
Raw clay, which is mined in mines and quarries, consists of 80-90% of flint sand. To separate ocher particles from it, the raw materials are washed in several stages and then dried. To obtain a red pigment, the mass is exposed to a temperature of 800-900 ° C. After cooling, the ocher is ground to 50 microns, graded for quality and color, and packaged.
To obtain the required colors, it is necessary to mix several types of ocher obtained from different ores.
Modern large producers of ocher are located in the USA, France, and some other European countries. This natural pigment is used in the construction industry to add color to finishing mixtures, in agriculture it is added to fertilizers. Since ocher is non-toxic, it is found in artistic oil paints and cosmetics. She plays an important role in the painting of pottery and ceramics, in the decoration of buildings. Colored sands left over from the production of ocher are also used: electric and telephone companies fill trenches with them.