Birch Tar through primitive technology

This is the third and final blog in a series about birch and its uses. In the first blog we covered the many uses attributed to it before focusing on birch oil gained through the dry distillation process. This is the oldest transformative process known to our ancestors, dating back thousands of years. In the second blog we looked at how you could use modern materials in the form of metal tins to achieve the process of extracting oil from birch bark in a step-by-step guide. In this third and final blog we’ll look at how our ancestors may have achieved similar results without the aid of any modern materials, to give similar results.

So, how far back does dry distillation go. Thermosetting adhesives are one of the earliest transformative technologies known to our ancestors. It’s thought it goes back at least 200,000 years, so let’s look at the evidence to support this.

Birch bark

On our own shores in North Yorkshire, there is a Mesolithic site, located at Steamer near Scarborough. It is known as Star Carr (site 4) and is recognised as being 11,000 years old. This site has revealed some of the most exciting artifacts to have been found relating to this very process. Credit for the discovery of Mesolithic hunter-fishers’ artifacts in the area goes to Mr John Moore, in the summer of 1947. At Star Carr the discoveries we are interested in this blog included actual rolls of birch bark! That largest of which measured 8” x 30” when unrolled. It was not decisive on its intended purpose other than it was actively collected, rolled, and stored in this way. No evidence of charring for torches or stitching for containers was found on site, but rather for the purpose of extracting the oil for transforming into a thermosetting adhesive to affix arrowheads and spearheads to shafts. Evidence of its use is found on a microlithic arrowhead embedded in birch tar and two barbed arrowheads with birch tar on their tangs. Other evidence suggests the dry distillation process was performed on this site with the discovery in 1951 of many thin flat cakes identified as either wood pitch or natural resin.

Publication documenting the discoveries at Star Carr

Older evidence of tar lumps has been found on tools at two different sites in Germany dating 40-80,000 years ago from the Middle to Upper Palaeolithic, with the second up to 120,000 years old in the Middle Palaeolithic.

Further back still from the Middle Palaeolithic (300,000 – 70,000 years ago) there has been discovered, two birch bark tar hafted stone tools foundinCampitello Quarry in Italy. The discovery was made in November 2001 alongside animal remains, making them at the time the oldest stone tools hafted with birch tar.

Ok so without the advantage of a tin of roses and an empty baked bean tin from my previous blog, how did they do it all those years ago? In understanding how this may have been possible, we can turn our attention to a scientific report published on 31 August 2017 from the Netherlands by, P. R. B. Kozowyk, M. Soressi, D. Pomstra & G. H. J. Langejans, where they aimed to answer that very question.

With what we knew from evidence previously discovered three experiments were devised to try and get a closer understanding to how our ancestors achieved their results.

Birch, bark used for tar and wood used for utensils

The first experiment was an “Ash mound”. A roll of birch was tied up using plant fibres and places on the floor. Ash and embers were then used to cover the roll of birch bark and left for a time. Upon removing the embers and ash, tar was observed of having collected in between the layers of birch bark. A quantity of 1g of tar for every 100g of birch bark used was produced.

The second experiment was a “Pit Roll”. Again, birch bark was rolled up to measure 6cm in diameter, but this time placed in a hole (8cm deep) in the ground, on top of a stone, which was there to collect the tar. Burning embers were then placed on top of the birch roll and left. Upon examination 2.4g of tar was produced to every 100g of birch bark used, over double the yield of the first experiment, but still just a small amount.

The third and final experiment was a “Raised Structure” A small birch bark container was placed in a small hole, over which organic matter was placed over the hole to act as a mesh. A roll of birch bark measuring 15cm in height and 15cm in diameter was placed upon the mesh. A mound was made over the birch bark roll and a large fire lit on top of it. The results revealed here were far more impressive. It produces enough tar to form a 10mm thick disc of tar measuring 45mm across. This mirrored what was found at Star Car. This equated to 9.6g of tar produced for every 100g of birch bark used or 15.7g in total. Effective results with only the use of items available 200,000 years ago.

The results of our birch burn in our previous blog

This resulted in only 11.04g per 100g of birch bark less than using modern metal containers in my previous blog, where we packed 224.4g of bark into the large tin. Which resulted in 60.1g of tar equating to 26.74g per 100g of birch bark. Due to the tins efficiency more volatiles were retained and the removal of them would of reduced the 11.04g considerably.

Hope you found this blog and the two which proceeded it insightful, we may not be able to go back in time to realise how our ancestors solved problems, but next time you find yourself looking at museum exhibits using birch tar, you’ll now be able to come closer to how our ancestors were able to produce them.


Cover Image, Jay in his happy birch place, which is Sweden.

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