Technological and physical aspects of experimental manufacturing thin bifaces of the initial Upper Palaeolithic in the Altai

From the theoretical and practical perspective this article analyzes technological and physical aspects of using hammers of different types and shapes in experimental cycle of manufacturing thin bifacial tools from raw materials known from the Altai Paleolithic assemblages. This study addresses the issues of producing bifacial shapes with hard mineral hammer in artificially controlled increase of radial velocity of the hammer, and use of wooden hammer as equivalent of antler hammer in its shape and therefore also in impulse force associated with it. According to the working hypothesis, control of the initial impact should be one of the key factors in achieving effective secondary thinning. The research has shown that elongated tool with greater initial impact force due to its natural shape (antler, wood) gives main advantages in biface creation. According to our data, only an antler hammer was capable of fully effective secondary thinning using the Altai raw materials. Increasing impact force with a mineral hammer gave a reduced number of successfulflakes. Wooden hammer, even under conditions of artificially increased initial speed, was effective only at the stages preceding secondary thinning. Although it is possible to counteract negative aspects of using wood, for this purpose a larger area should be created by additional thinning thereby decreasing the width of the biface too rapidly, which will not make it possible to reach the ratio of width to thickness corresponding to "thin biface.”