Discoloration of varnishes and varnishes. simple recipes

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FACTORY TECHNOLOGIES AT HOME - SIMPLE RECIPES
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Discoloration of varnishes and varnishes. Simple recipes and tips

Factory technologies - simple recipes

Directory / Factory technology at home - simple recipes

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Many drying oils and varnishes, used for special purposes, must be completely colorless.

When preparing varnishes from the lightest resins, we still get a more or less yellow color. To bleach varnishes and drying oils, they are treated for a long time with bone charcoal. The process is that bone charcoal is loaded with varnish and infused in a warm place. Bone charcoal has the ability to absorb dyes. After bleaching, the varnish is filtered.

Bone charcoal is obtained by burning defatted and cleaned bones without access to air. Defatted coal is treated with hydrochloric acid to remove the salts it contains. For this purpose, 10 kg of coal is placed in large vats, into which 7 kg of hydrochloric acid is poured. The mixture is left for one day with frequent stirring, after which the coal is placed in a tub of water. The coal is thoroughly washed with water until the washing water gives an acidic reaction (test with litmus paper). The washed coal is dried.

Bone char loses its bleaching ability over time and is replaced by new char. In order to restore the properties of used coal to absorb dyes (regeneration of bone char), it is washed first with hydrochloric acid, then with water, then boiled with caustic soda and finally washed thoroughly with water. Typically, 1-0,5% hydrochloric acid is taken by weight of dry coal and diluted with water to obtain a 1% acid solution. The coal is poured with a solution of hydrochloric acid and left until bubbles begin to form. After 6-7 days, drain the solution and wash the coal thoroughly with clean water.

When washing, it is advisable for water to enter from below and leave from above (wooden or glazed dishes can be used as utensils for washing and processing coal), then boil with a weak solution of caustic soda, after which the coal is dried. Recently, steam treatment has been used instead of drying. Further processing is reduced to calcining the coal without air access in special furnaces.

Used coal treated in this way has the same properties as fresh coal and can be put into use.

Author: Korolev V.A.

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