Additional information
Shellac is actually not one of the usual soft resins and is not found in turpentine oil or white spirit soluble, but only in alcohol. It is neither a purely plant nor a purely animal product, but is created from In a strange way, very specific scale insects (lac dye) appear on young, sap-rich shoots in very different ways Plant species are bred where they absorb the plant sap as food into a resinous mass in the body and then sweat it out until the whole animal is thickly covered in it and finally dies. The branches, which are densely covered with tons of such lice, gradually become crusted up to 1 cm thick and as a result caused itself to die.
The so-called Stocklack (60430) comes from very different plants, but always from the same one Scale insect species produced. The bite of a scale insect, Tachcerdia lacca, occurs on various host plants (Croton, Schleichera, Ficus and other species) causes excretion, which gradually spreads to the infected Branches with scale insects covered in a thick, red, resinous mass. In this form the product is collected and is called Stocklack. In the Hindu language, "lakh" means a hundred thousand, which expresses that Huge quantities of scale insects are necessary to prepare paint. Through frequent washing, remelting and Finally, extremely skillfully, the thin, warm mass is pulled out between the feet and hands of the spread-out one The "leaf shellac" forms into a thin skin and breaks into numerous small pieces when it hardens. (60440, 60450), of which the light yellow and wax-free varieties are most valued by painters and gilders become.
There are an extraordinary number of types of shellac, which differ considerably in color, shape and wax content from the dark red "ruby shellac" (60480) to the yellow "lemon shellac" (60400). For This may be useful for gilding purposes or even bring advantages, but technically it is still far too rich in dyes. Selected "light blonde" varieties from India are usually only subjected to chemical treatment in Europe or other countries Subjected to bleaching process and then carefully washed again. Coatings of bleached shellacs are However, these procedures make it a little more brittle, but that doesn't bother me from a painting perspective, because it turns into shellac used mainly as an insulating agent or to make good fixatives for charcoal and pencil drawings. High-quality pastel fixatives are put together differently. It is also used to make shellac soap. Shellac leaves, when stirred into hot, alkaline borax solutions, produce resin soap, which can be used as a binding agent or as an additive can be used to form aqueous binders.
Giving recipes about solution ratios has practically little value, because the different Purposes require fundamentally different concentrations. For example, you can use alcohol (96% alcohol) prepare a stock solution in a ratio of 1:2 and then continue with alcohol or as required If necessary, dilute with denatured alcohol (96% alcohol, denatured with pyridine).
The stick varnish, as a raw material for shellac production, is converted into grain varnish (60490) in the countries of origin. further processed. The raw material is separated from the wood, ground and washed. This involves wood residue largely removed from the paint and most of the water-soluble dye contained in the resin (lac dye) washed out. Finally, the grain varnish is dried in the sun.
The grain varnish is a natural raw material with excellent environmentally friendly properties as the starting product available for shellac refinement: renewable, biodegradable and physiologically harmless. Different processes are used to process this raw material. In India, grain varnish has been painstakingly refined by hand into shellac for generations.
The raw material is enclosed in long, tightly woven cotton tubes over a covered fire carefully warmed. The paint is pressed through the cotton fabric, residues and impurities remain tissue back. The workers now grab the cleaned paint with their hands and feet and pull it into large pieces "Skins" are broken apart, which after cooling are broken into shellac leaves.
In the corresponding industrial process, the granular varnish is molten under high pressure pressed through filters and drawn out on a rolling belt to form a thin film, which, after cooling, goes into the typical leaves are broken.
Leaf varnish produced by melt filtration has a natural wax content of 3 to 5% and is therefore suitable Excellent for the production of furniture polishes, wood primers, sealants etc.
To create a dewaxed shellac of a lighter color, the grain varnish is soaked in alcohol dissolved, physically decolorized and goes through several filtration steps. Here he is freed from impurities cleaned and the wax removed. Finally, the alcohol is recovered and the shellac is rolled into one film and breaks it into sheets.
This process has decisive advantages over melt filtration. It's gentler and it can be done. Produce shellac of consistently high quality and with guaranteed properties that meet the requirements of the processing industry.
In contrast to physical decolorization, there is the bleaching process, which produces very light shellac leaves. The grain varnish is dissolved in an aqueous-alkaline solution, dewaxed, filtered and then chemically bleached. After precipitation, washing and drying, a light yellow powder is obtained.
