The experimental modeling of asbestos-tempered vessels

Abstract

The tradition of mixing asbestos into pottery clay originated near the deposits of this mineral on the lake Saimaa (Finland) in the 5th millennium BC. By the second half of the 4th millennium BC its area reached the Arkhangelsk and Vologda Regions of Russia in the east. The aim of the work is to review the functional hypothesis, according to which the widespread use of asbestos as an admixture is due to its advantages over other additives facilitating the process of molding and drying, preventing flaws during firing, making the vessel durable and easy to use. According to the results of our experiments on the making of vessels and model samples with asbestos it turned out that the used asbestos of the Chevzhavara deposit (tremolite-ferroactinolite) does not have such advantages. The most important problem was the dissociation of asbestos at temperatures above +700C. After such firing, the vessels were destroyed, and the asbestos itself became brittle. It can be assumed that in order to minimize losses during the firing, the ancient potters could beforehand hold the asbestos at a high temperature so that it would lose the main amount of water but keep its stability. It can be preliminarily concluded that asbestos admixture at an early stage of use did not have clear advantages over other additives. The reasons for the initial interest in asbestos as an additive could be other, e.g. socio-cultural. A special developed technology for processing asbestos, which made it possible to use its advantages, spread around the beginning of the Bronze Age and may be associated with the beginning of metalworking.