Birch (bark)
tar or birch
pitch is a substance (liquid when heated) derived from the
dry distillation of the bark of the
birch tree.
Chemical composition
Birch tar/pitch is mainly composed of
triterpenoid compounds of the
lupane and oleanane family, which can be used as biomarkers to identify birch tar in the archaeological record. The most characteristic molecules are
betulin and
lupeol which are also present in birch bark.[1][2] Some of these molecules degrade into other lupane and oleanane skeleton triperpenes. The most commonly found additional molecules are lupenone, betulone, lupa-2,20(29)-dien-28-ol, lupa-2,20(29)-diene and allobetulin.[3][4][5]
Ancient and modern uses
Birch tar was used widely as an
adhesive as early as the Middle
Paleolithic to early
Mesolithic era.
Neanderthals produced tar through the dry distillation of
birch bark as early as 200,000 years ago.[6] A study from 2019 showed that birch tar production can be a very simple process, merely involving the burning of birch bark near smooth vertical surfaces in open air conditions.[7] However, at Königsaue (Germany), Neanderthals did not make tar with this method but rather employed a technically more demanding underground production method.[8] A find from the Dutch North Sea[9] and two tools from the Italian site Campitello show that Neanderthals used birch tar as a backing on small 'domestic' stone tools.
A piece of 5,000-year-old
chewing gum made from birch bark tar and still bearing tooth imprints, has been found in
Kierikki in Finland.[10] Genetic material retained in the gum has enabled novel research regarding population movements, the types of foods consumed, and the types of bacteria found on their teeth.[11]
A different chewing gum sample, dated to 5,700 years old, was found in southern
Denmark. A complete
human genome and oral
microbiome was sequenced from the chewed birch pitch. Researchers identified that the individual who chewed the pitch was a female closely related genetically to
hunter-gatherers from mainland Europe.[12]
Ends of
fletching of
arrows were fastened with birch-tar and birch-tar-and-
rawhide lashings were used to fix the blade of
axes in the Mesolithic period.
Birch tar was more frequently discovered in archaeological contexts dating from the
Neolithic to the
Iron Age. For example, birch tar was identified to serve as an adhesive to repair[13][14][15][16] and decorate/paint ceramic vessels,[17] as a sealing/waterproofing agent.[18][19] A well-known example of birch tar hafting during the copper age is
Ötzi’s hafted arrow points and copper axe.[20] Multiple discoveries show that birch tar was also used to assemble metal artefacts, such as pendants and other ornaments, on both a functional and decorative level.[21][22] During the
Roman Era, birch tar is mostly replaced by wood tar,[23][24] but birch tar is still used, for example, to decorate hinges and other bone objects.[25]
Russia leather is a water-resistant leather,
oiled with birch oil after tanning. This leather was a major
export good from seventeenth- and eighteenth-century Russia, as the availability of birch oil limited its geographical production.[26] The oil impregnation also deterred insect attack and gave a distinctive and pleasant aroma that was seen as a mark of quality in leather.
Birch tar
oil is an effective
repellent of
gastropods.[28] The repellent effect lasts about two weeks.[28] The repellent effect of birch tar oil mixed with
petroleum jelly applied to a fence lasts up to several months.[28]
Birch tar oil has strong antiseptic properties[29] owing to a large amount of phenol derivatives and terpenoid derivatives.
Birch tar oil was used in the eighteenth century alongside
civet and
castoreum and many other aromatic substances to scent the fine Spanish leather
Peau d'Espagne. At the turn of the twentieth century, birch tar has become a specialty fragrance material in
perfumery as a base note to impart a leathery, smoky note in fragrances, especially from the leather and tobacco genre, and to a lesser extent in
Chypres, especially
Cuir de Russie perfumes and fragrance bases, typically together with castoreum and isobutyl quinoline. It is used as an ingredient in some soaps, i.e. the scent of
Imperial Leather soap, though other tars (i.e. from pine, coal) with an equally phenolic and smoky odour are more commonly used in soaps as a medicating agent.
References
^Hayek, E.W.H., Jordis, U., Moche, W., Sauter, F., 1989. A bicentennial of betulin. Phytochemistry. 28, 2229–2242.
^Hayek, E.W.H., Krenmayr, P., Lohninger, H., 1990. Identification of Archaeological and Recent Wood Tar Pitches Using Gas Chromatography/Mass Spectrometry and Pattern Recognition.
^Aveling, E., Heron, C., 1998. Identification of Birch Bark Tar at the Mesolithic Site of Star Carr. Ancient Biomolecules. 2.
^Regert, M., 2004. Investigating the history of prehistoric glues by gas chromatography-mass spectrometry. journal of separation science. 27, 244–254.
^Rageot, M., 2015. Les substances naturelles en Méditerranée nord-occidentale (VIe-Ie Millénaire BCE) : chimie et archéologie des matériaux exploités pour leurs propriétés adhésives et hydrophobes (Doctorat). Université Nice Sophia Antipolis.
^Bosquet, D., Regert, M., DUBOIS, N., Jadin, I., 2001. Identification de brai de bouleau sur quatre vases du site rubané de Fexhe-le-Haut-Clocher «Podrî l’Cortri». Premiers résultats.
^Urem-Kotsou, D., Mitkidou, S., Dimitrakoudi, E., Kokkinos, N., Ntinou, M., 2018. Following their tears: Production and use of plant exudates in the Neolithic of North Aegean and the Balkans. Quaternary International. 496, 68–79.
^Urem-Kotsou, D., Stern, B., Heron, C., Kotsakis, K., 2002. Birch-bark tar at Neolithic Makriyalos, Greece. Antiquity. 76, 962–967.
^Rageot, M., Lepère, C., Henry, A., Binder, D., Davtian, G., Filippi, J.-J., Fernandez, X., Guilaine, J., Jallet, F., Radi, G., Thirault, E., Terradas, X., Regert, M., 2021. Management systems of adhesive materials throughout the Neolithic in the North-West Mediterranean. Journal of Archaeological Science. 126, 105309.
^Morandi, L.F., Porta, S.N., Ribechini, E., 2018. Evidence for Birch Bark Tar Use as an Adhesive and Decorative Element in Early Iron Age Central Italy: Technological and Socio-Economic Implications. Archaeometry. 60, 1077–1087.
^Hayek, E.W.H., Krenmayr, P., Lohninger, H., 1990. Identification of Archaeological and Recent Wood Tar Pitches Using Gas Chromatography/Mass Spectrometry and Pattern Recognition.
^Regert, M., Vacher, S., Moulherat, C., Decavallas, O., 2003. Adhesive Production and Pottery Function During the Iron Age at the Site of Grand Aunay (Sarthe, France)*. Archaeometry. 45, 101–120.
^Sauter, F., Ulrich, J., Graf, A., Werther, W., Varmuza, K., 2000. Studies in organic archaeometry I: identification of the prehistoric adhesive used by "Tyrolean Icemen" to fix his weapons. Arkivoc. V, 735–747.
^Regert, M., Rolando, C., 2002. Identification of Archaeological Adhesives Using Direct Inlet Electron Ionization Mass Spectrometry. Analytical chemistry. 74, 965–75.
^Courel, B., Schaeffer, P., Féliu, C., Thomas, Y., Adam, P., 2018. Birch bark tar and jewellery: The case study of a necklace from the Iron Age (Eckwersheim, NE France). Journal of Archaeological Science: Reports. 20, 72–79.
^Balsan, L., 1951. L’industrie de la résine dans les Causses et son extension dans l’empire romain. Gallia. 9, 53–55.
^Trintignac, A., 2003. La production de poix dans la cité des gabales (Lozère) à l’époque gallo-romaine. RAP. n°1/2, 239–248.
^Regert, M., Rodet-Belarbi, I., Mazuy, A., Dantec, G., Dessì, R.M., Henry, A., Rageot, M., Briz, S., 2019. Birch bark tar in the Roman world: the persistence of an ancient craft tradition. Antiquity. 93.