Wood tar - a natural and safe product to protect wood from moisture and insects

Discussions on the use of tar are contradictory, with some claiming that 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. Tar made from wood is a material with very good properties for protecting 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 (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 bit of a black cone. 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, there is evidence of its use in ancient Greece and even in the Iron Age. The star of the last 5-6 centuries has been pine tar produced in the Nordic countries and Russia. Because there were large areas covered with pine forests, the inhabitants found all sorts of ways to use the wood, including stumps and roots. One of them was to heat it at high temperatures, without burning, in special ovens built into the ground. At the base of the specially built kiln, tar, a thick brown, pleasant-smelling, brown mixture, oozed out.

In the 17th century such kilns existed in most towns in Sweden, Finland and Norway. Because of its water-protective properties it was used in shipbuilding and thus came to be exported to the surrounding countries poorer in forests. Because the raw material was not the same and the quality of tar differed from locality to locality, from country to country. The most highly prized tar came from northern Sweden, where the first export company under the patronage of the King of Sweden was established. This was Sweden's main tar exporter from 1650 until the beginning of the 20th century, and exports were made via the port of Stockholm. The tar was packed in wooden barrels stamped with the port's name, so that Stockholm tar has become synonymous with quality.

Another major producer of tar was the USA, the method of production being exported by settlers. The main beneficiary was Great Britain, which used it to protect the wood, decking and sails of the boats it built against water. It was a period of great development in this field, spurred on 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 emergence of modern wood preservatives also led to a drastic drop in production in the early 20th century.

And we got tar in the Margina factoryin 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 was closed in 1998.

Making tar from wood

Tar is obtained by the destructive distillation at high temperature of materials such as wood, oil, coal or peat. In name, 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 either from both hardwood and softwood. The main difference is the specific odor of the resinous one due to the terpenes derived from the resin. The most popular types of tar are pine tar and birch.

Up distillation of wood is carried out at 500°C resulting in a mixture of gases and vapors, tars and char. The gaseous mixture is then condensed, the resulting liquid part being a mixture of wood tar and pyroligneous acid, 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). Resinous wood tar is a viscous liquid with a specific odour and a colour ranging from orange-brown to brown. It can be used as such for the protection of craft wood, in the rubber and pharmaceutical industries. Hardwood tar is further processed to obtain wood tar oils and wood creosote.

Processing wood at such high temperatures is now easily done in sophisticated industrial plants. In the past, however, the wood had to be heated without igniting. To do this, funnel-shaped furnaces were built in 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 earth and moss to protect the wood from the oxygen in the air that would ignite it. Dry firewood was made on top and the wood in the kiln was heated to release the tar that was collected at the base.

Use of wood tar

Wood tar is not only used to protect wood against moisture. It has many 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 the sauna, vodka and tar don't help, the disease is definitely fatal. Pine tar is used in traditional Finnish medicine for 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 soap, shampoo (to combat dandruff) and in various creams and oils. It is used in a wide range of industries, from tree treatment to metallurgy. In addition to pine tar, there are other specific types of tar such as birch bark tar, also called Russian oil (very fine, used to protect the skin) or red juniper tar, used in the pharmaceutical and soap industries.

Protecting wood with pine tar

Pine tar (in the English documentation you will find it as pine tar or swedish tar) protects the wood very well against water, moisture and insects, including termites. It is a thick liquid that needs to be heated to 60°C in 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 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.

Old Nordic recipes for treating wood included one third pine tar, one third turpentine and one third linseed oil or tung oil Chinese. Now use diluted with turpentine or turpentine and linseed oil. Apply 2-3 coats, drying in between so that the wood absorbs very well. Finally apply 3-4 coats wet on wet for very good protection. The protected wood can last up to 20 years. The durability depends on exposure and climate.

Tar is also used in industrial paints or varnishes for exterior use. Different colors can be obtained by mixing with pigments.

It is still badly needed

Wood tar is used mainly in marine applications, but also as a sealant in construction. Although it may seem a product of the past, are studies predicting a steady increase in the use of in shipbuilding activities, and significant opportunities in the pharmaceutical and cosmetics industries will arise in the coming years. Of the tars, resinous 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, tar is not produced here. The kind made in the Nordic countries or the USA is hard to find in shops. But you can find it online. You can also find tar made in Asia, which is also becoming important in this area.

I hope you found the information interesting. If you have any clarifications or questions, leave them below in the dedicated space. I will certainly reply.