1st Experimental Archaeology Conference Abstract – Bastian Asmus
From the 1st Experimental Archaeology Conference, UCL, London, 2006.
Design and Use of Natural Draft Furnaces for Bronze Casting
UCL Institute of Archaeology, 31-34 Gordon Square, London WC1H 0PY
This paper is concerned with the design and use of bronze casting natural draft furnaces. It demonstrates the possibility to use such a furnace with and without artificial oxygen induction by means of bellows and/or tuyeres. It challenges the implicitly accepted concept that high temperature processes in furnaces necessarily require additional air supply. It explores furthermore resulting problems of crucible handling, fuel charge and gas flow in the suggested furnace designs. The archaeological record lacks furnaces as well as tuyeres, at least in proportion to the overwhelming number of metal objects. If furnaces are present, they usually lack a superstructure. The number of tuyeres we find is too small to assume their use for all high temperature processes. But this is only a mystery if we assume as necessary the use of bellows for melting metals. There are three possible alternative solutions for this:
tuyeres are not yet found, due to limited archaeological research
you do not need bellows
you do not need tuyeres
The experiments presented here tested the latter two possibilities. The outcome clearly suggests the use of both furnaces without bellows and furnaces with bellows but without tuyeres. It will be demonstrated that bellows are not necessary to achieve high temperatures, although the use of bellows can greatly facilitate the control over the furnace temperature. Tuyeres are not obligatory at all for inducing oxygen into the furnace.