Wood tar gives a weak brown colour, due to coal dust and pitch. Pigments such as red or yellow ochre can be stirred in. To improve applicability, the tar is most often supplemented with linseed oil or alkyde oil and thinned with organic solvents; fungicides can also be added.
Wood tar is extracted from both coniferous and deciduous trees and is usually rich in polycyclic aromatic hydrocarbons (PAHs). An exception is tar extracted from beech. PAH substances such as benzo(a)pyrene are carcinogenic and mutagenic. Tar products should not be used indoors. When used outdoors, the PAH substances will filter into the soil.
Re-use and recycling of painted products can be a problem. As waste, the product should be deposited at special dumps.
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