Since ancient times, people have been looking for useful plants that have coloring properties. For painting, dyeing fabrics and various products used a variety of natural dyes that are contained in the bark, leaves, flowers of plants. The modern color palette has several million shades, tones and midtones, among them one of the most popular is alizarin color.
Description
Alizarin crimson belongs to a transparent shade of red, gravitates to a violet tone, is closest to a crimson color. The international index is PR83 in the category of red pigments. Alizarin red color got its name thanks to a natural organic dye - alizarin.
History
The plant Rubia Tinctorum, or madder, is known as a source of dyes for a long time. In ancient times, the inhabitants of Egypt, Persia, India, Smyrna used dried and crushed madder root to obtain red-pink dyes, including expensive and rare purple. Merchants who brought the madder root from the Levant and Cyprus, called it the same as the locals - lizari, alizari. With this name, dye entered the history that Pliny Sr. captured on the pages of his books.
The yellow-red dry powder was diluted with clay chalk and gorgeous bright red colors were obtained, which dyed cotton, silk, and woolen fabrics.
Alizarin in Europe
Madder was grown throughout Europe - because the plant gave a net profit. Dyes from madder growing in Avignon (France), Bavaria, Belgium, Alsace, Holland were especially appreciated. In the XIX century The Free Economic Society of the Russian Empire awarded scientists for the cultivation of new varieties of madder, which was cultivated in the Caucasus, Crimea, and in the vicinity of Samarkand.
Huge areas were allocated for madder, growing a profitable culture on thousands of square kilometers. The cost of 1 kg of alizarin was 100 francs. World production of madder root per year in the middle of the XIX century exceeded 70 million francs. But soon the organic dye was replaced by a chemical compound.
Some chemistry
Natural alizarin was obtained from dried madder root, based on the coloring effect - the decomposition of ruberitric acid into a sugar substance and alizarin. In 1826, French chemists Robik and Colene synthesized pure alizarin color, the name has remained the same.
At first, the substance is considered to be a derivative of naphthalene, only in 1868 Lieberman and Grae reported a successful experiment in the synthesis of alizarin from coal anthracene using an alkaline oxidation reaction. The patent was recognized in all countries of the world, including America and Russia.
For the first time in history, vegetable dye was obtained artificially. This discovery was called one of the largest in economic importance. After all, synthetic dye was cheaper, more affordable than natural, and besides it had increased strength: the artificial alizarin color did not fade in 9-12 months in direct sunlight.
Industrial production was established much later, in the 70s of the XIX century, when the synthetic methods for obtaining dye were improved. Thanks to this, the vast fertile territories planted with madder were liberated under other cultures.
Dye production
Alizarin color for the first time in industrial volume began to produce a factory in Baden, but a year later, 6 German factories produce synthetic dye. Soon they were joined by factories in Switzerland, England and Austria. In pre-revolutionary Russia, only the L. Rabenek plant located in Moscow was doing this. He produced about 100 tons, while the needs of Russian industry amounted to more than 400 tons.
Modernity
The alizarin palette changes from violet (pH12) to yellow (pH5.9). In combination with metal ions, alizarin gives insoluble alizarin varnishes, or chelate complexes, indispensable in printing. Alizarin color in the photo looks bright and elegant.
Now the dye is produced from 99% anthraquinone, which is subjected to a sulfonation process in an autoclave at a pressure of 12 atmospheres. The precipitate obtained as a result of interaction with sulfuric acid is passed through a wooden filter. Alizarin was indispensable for dyeing natural tissues (plant and animal fibers). The substance gives not only a juicy alizarin color, but depending on the organic compounds (mordants), different colors can be obtained:
- with alumina-calcium - red-blue;
- on iron - purple, blue;
- on chrome - red-brown.
Shades of alizarin are always durable, do not fade in the sun, do not fade, do not wash. In the 80s of the XX century. Alizarin is replaced by chemical dyes, for example, para-red, naphthol AC. However, only alizarin is cheap and durable.
Alizarin color in art
To obtain paints, crushed and dried madder root was mixed with oils or organic compounds to obtain a stable dye. Red tones were obtained by mixing alizarin with tin oxides and alumina, dark blue and violet with iron oxides, and a brown gamma with chromium salts.
Many Renaissance artists mixed paint in this way, painted not only paintings, but also murals. Natural dyes were mainly used until the middle of the 20th century. Experts consider Avignon paints to be the highest quality.
In the United States, the television host and artist Bob Ross popularized the professional name of the red hue. During his television shows, he talked about the possibility to paint a picture in half an hour or an hour using ready-made basic elements. He often showed alizarin color. This is what shade, not many knew.
Alizarin ink - what is it really?
Dye from madder root is not part of this type of ink; they are made from ink nuts, acetic acid, iron sulfate, and gum arabic. A bright alizarin color appears in the ink thanks to a solution of indigo carmine. The difference between alizarin inks and others is that, due to glue and acid, the coloring matter does not precipitate.