Watercolor cobalt blue 3.2 ml

The composition of watercolors uses finely ground, concentrated pigments and highly purified gum arabic. A high degree of grinding on a ceramic paint mill produces transparent, pure and saturated colors. Watercolors mix well, are easily washed off and have high lightfastness.

Thenard's azure, royal blue, cobalt ultramarine, Hans ultramarine, Wenzel's azure, Leydsrow, sapphire, Leyden blue. The first cobalt paint that began to be used in painting was schmalt (smalt). The discovery of schmalt is usually attributed to the middle of the 16th century. Although "Egyptian blue" is quite comparable in composition to modern cobalt smalts, which were used in Ancient Egypt (early 1 millennium BC) as a blue pigment, as well as for glass painting. The use of many components and various technologies for obtaining pigments by ancient painters does not allow us to unambiguously determine the composition of Egyptian blue paint. Cobalt blue paint was "rediscovered" in 1804 by Louis Jacques Thenard.

An artificial pigment, by composition - cobalt aluminum oxide C0AI2O4, which may include aluminum oxide (lighter) and zinc (greenish), and sometimes Mg and P (reddish). A more correct composition of cobalt blue is cobalt aluminate CoOxAЬO3 with a small amount of zinc oxide impurities introduced into the composition not to form paint, but to improve the color and obtain a variety of shades.

The coloring ability of cobalt blue is low. The pigment is light-, heat- and weather-resistant. In evening light, dark blue cobalts lose color, becoming black.

A rich bright blue color, with coarse grinding the saturation decreases. To improve the color, small amounts of additives are introduced into its composition - violet cobalt Coz(РС>4)2 and green cobalt CoOxnZnO, and the presence of free aluminum oxide makes the pigment lighter. The coloring principle, i.e. cobalt oxide, in Thenard blue is no more than 2%, the rest is aluminum oxide and zinc oxide. Due to the low content of cobalt oxide in the paint, the pigment loses color to a certain extent: in oil painting - when the oil turns yellow, in watercolor - when the paper turns yellow. When removing yellowness in paper and oil, the discolored cobalt blue again acquires its original color.

The coloring ability of cobalt blue is low. The pigment is light-, heat- and weather-resistant. In evening light, dark blue cobalts lose color and appear black. The paint is much more resistant to acids than ultramarine. The pigment is resistant to acids and alkalis, decomposes when boiled in sulfuric or hydrochloric acids.

Due to the close refractive indices of cobalt and oil, cobalt blue has a glazing ability; to further increase the glazing ability, the content of Al2O3 is increased. It dries quickly on oil and dries the paints mixed with it, and its layer is often covered with cracks. The latter circumstance is explained by the fact that cobalt compounds (especially cobalt acetate) are the strongest siccatives for oils. All cobalts are siccatives, mixtures of other oil paints with them dry quite quickly, but there is a fear that the paint coating will crack.

In mixtures with other paints, cobalt blue hardly changes, retains strength. But its mixtures with madder and lead white are not recommended (the former are somewhat destroyed, and the latter slightly darken). Cobalt blue tends to turn green in low light conditions in pastose layers due to yellowing of linseed oil, which turns into linoxyn when dry.

•Chemical description: watercolor paint, semi-dry, in a 3.2 ml cuvette

•Color index PB 28

•Alkali resistance: 5

•Lime resistance: 5

•Acid resistance: 5

•Lightfastness - 8

•Color dark blue

•Form cuvette 3.2 ml