Discussions on the use of tar are conflicting, with some claiming it is a miracle material, others that it is particularly dangerous. Paradoxically, they are all right, because tar can be made from different materials, with different results. Wood tar is a material with very good protective properties for wood outdoors or in particularly damp conditions. It is different from oil or coal tar, which is considered dangerous because of its high benzene content (considered a carcinogen). Used extensively in the past to protect wood, especially boats, the advent of modern wood products and the move away from wood in shipbuilding has put wood tar as a wood preservative in a shadow. But it continues to be used because its properties go far beyond wood protection.
Just a bit of history
Wood tar has been known since ancient times, with evidence of its use in ancient Greece and even in the Iron Age. The one that has been the star for the last 5-6 centuries has been pine tar produced in the Nordic countries and Russia. Since there were vast areas covered with pine forests the inhabitants found all sorts of ways to use the wood, including stumps and roots. One way was to heat it at high temperatures without burning it in special kilns built into the ground. At the base of the specially built kiln, tar, a thick brown and pleasant smelling mixture, was poured out.
In the 17th century such ovens existed in most places in Sweden, Finland and Norway. Because of its water-protective properties it was used in shipbuilding and thus ended up being exported to surrounding countries poorer in forests. Because the raw material was not the same and the quality of the tar differed from locality to locality, from country to country. The most prized tar came from northern Sweden, where the first export company was established under the patronage of the Swedish king. It was Sweden's main exporter of tar from 1650 until the beginning of the 20th century, and exports went through the port of Stockholm. The tar was packed in wooden barrels stamped with the name of the port, so that Stockholm tar has become synonymous with quality.
Another important producer of tar was the USA, the method of production being exported by the colonists. The main beneficiary was Britain, which used it to protect the wood, timbers and sails of the boats it built from water. It was a period of great development in this field, encouraged by the emergence of American industries and the increased demand from Britain following the occupation of the northern countries by the Tsarist Empire. The replacement of wood by metal in shipbuilding and the advent of modern wood preservatives also led to a drastic drop in production in the early 20th century.
And we got tar in the Margina factoryfrom Timiș county. The foundations of the factory were laid in 1910, and the tar was obtained as a by-product of distillation beech wood, the main product being wood vinegar. The factory went into decline after 1990 and closed in 1998.
Obtaining wood tar
Tar is obtained by the destructive distillation at high temperature of materials such as wood, oil, coal or peat. Tar and pitch mean the same thing, except that it is common to use the term pitch for the solid product and tar for the liquid. Wood tar can be obtained from either both softwood and hardwood. The main difference is the specific smell of the resinous one due to the terpenes coming from the resin. The best known types of tar are pine and birch.
The wood is distilled at 500°C resulting in a mixture of gases and vapours, tars and char. The gaseous mixture is then condensed, the resulting liquid part being a mixture of wood tar and pyroligneous acid, subsequently separated by distillation. The main components of pyroligneous acid are acetic acid (wood vinegar), methyl alcohol and denatured spirit (a mixture of alcohols and acetones). The resinous wood tar is a viscous liquid with a specific odour and ranges in colour from orange-brown to brown. It can be used as such for the protection of craft wood, in the rubber or pharmaceutical industries. Hardwood tar is further processed to obtain tar oils and wood creosote.
Processing wood at such a high temperature is now easily done in sophisticated industrial plants. In the past, however, wood had to be heated without igniting. To do this, funnel-shaped furnaces were built into the ground with the possibility of tar leaking out at the bottom. The walls were lined with wood, and inside were finger-sized pieces of wood and roots. The whole thing was covered with soil and moss, keeping the wood away from the oxygen in the air that would cause it to ignite. Dry wood was burned on top and the wood in the kiln was heated to release the tar that was collected at the bottom.
Use of wood tar
Wood tar is not only used to protect wood against moisture. It has a host of other uses, many of which have been known since ancient times. In Finland for example, wood tar was considered a panacea that was supposed to cure you of any illness no matter how serious. A Finnish proverb says if sauna, vodka and tar don't help, the disease is surely fatal. Pine tar is used in traditional Finnish medicine because of its anti-microbial properties.
Wood tar is used in the cosmetics, pharmaceutical (human and veterinary), paint production, construction and rubber industries. In cosmetics, it is used in the manufacture of soap, shampoo (to combat dandruff) and in the composition of various creams and oils. It is used in a wide variety of fields, from tree treatment to the metallurgical industry. In addition to pine tar, there are other specific types of tar such as birch bark tar, also called Russian oil (very fine, used for skin protection) or red juniper tar, used in the pharmacy or soap industry.
Protecting wood with pine tar
Pine tar (which in English documentation you find as pine tar or swedish tar) protects wood very well against water, moisture and insects, including termites. It is a thick liquid that needs to be heated to 60°C on a water bath before it can be used. Drying is very slow and can take several weeks., depending on climate and temperature. However, you must wait because otherwise stains will result when finishing. It is a 100% natural finish, with very good moisture resistance and is still used to protect traditional wooden boats.
The old Nordic recipes for treating wood had in their composition one third pine tar, one third turpentine and one third linseed oil or tung oil Chinese. Now used diluted with turpentine or turpentine and linseed oil. Apply 2-3 coats, with drying in between, so that the wood absorbs very well. Finally apply 3-4 coats wet-on-wet for very good protection. Wood protected in this way can last up to 20 years. However, the durability depends on exposure and climate.
Tar is also used to make industrial paints or lacquers for outdoor use. Different colours can be obtained by mixing with pigments.
It is still badly needed
Wood tar is mainly used in marine applications, but also as a sealant in construction. Although it seems a product of the past, are studies predicting a steady increase in the use in shipbuilding activities, and significant opportunities will be created in the pharmaceutical and cosmetics industries in the coming years. Of the tars, resin tar is expected to have the largest market share due to its widespread use in marine coatings and pharmaceuticals.
Unfortunately, as I have already said, we do not produce tar. Tar made in the Nordic countries or the USA is hard to find in shops. But you can find it in the online trade. You can also find tar made in Asia, which is also becoming important in this area, in the online trade.
I hope you found the information interesting. If you have any queries or questions, please leave them in the space below. I will certainly answer them.
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