Dear Stefanie,
I assume that you are talking about the bellows-protectors. Tylecote
has illustrations block tuyeres in his 'The Early History of metallurgy in
Europe' Longman Archeology Series 1987, p 118-120. I have come across clay
plates from Oxfordshire that have been used as tuyeres which have been
mis-identified. The shapes vary, but those from the Iron Age and Romano-British
period are either like short fat tuyeres (round), possibly block tuyeres, or
rectangular plate with a central hole 2-2.5cm diameter (for iron-working) of
unknown thickness. These were usually represent by fragments of
the hole and a little of the surrounding clay is found so the shape can not
be worked out - this material is often label burnt daub. However, the shape of
the hole and the surrounding vitrification is unlike features normally seen on
burnt daub.
In some cases both the hole and the edge of the plate were preserved,
as these fragments had either curved edges or flat edges the material was
described as loom weights. In one case, I think from Gravelly Guy, was a
quarter plate with the base and sufficient of the upright edge preserved to
show that it was part of a rectangular plate of unknown thickness but at least
3-4cm. Another feature sometime present is that there is a mixture of fused
soil and charcoal fused to the under-side of the bottom edge of the plate.
In smithing experiments I performed years ago, the exact same thing
happened to my experimental reconstuction. If the hearth is set up directly on
the soil, a blast of very hot air is reflected back under the plate and
gradually eroded a small pit under the central portion of the plate. With time
this are becomes so hot that semi-fused soil eroded from the base of the
hearth and slag start sticking to the base of the plate. The experimental plate
was 3cm thick, made of the local clay. It lasted a couple of days then started
to break, in exactly the same manor as the archaeological examples.
Unfortunately, as far as I know none of this material has been
published.
As a note to Irene's comments. Finds of tuyeres are rare in relation to
British iron smelting, the preference being for simple blowing holes throught
the furnace wall.
Chris Salter
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