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The First (Biscuit)
Firing:
We still have not spoken of one of the properties
that characterises clay, and that is its FRAGILITY.
This characteristic gives the craftsman particular cause for
apprehension, especially when it is completely dry: it only need a
little knock for the sputed jar in the photograph here to shatter
into small pieces. As if by magic, or rather by the clay’s
refractory qualities, heat treatment (FIRING)
causes loss of plasticity and replaces it with HARDNESS
and STRENGTH whilst
leaving the shape unaltered. In Deruta, with the type of clay that
we use, the first firing takes place at around 1000°C.
The object is placed in the kiln, and after about 8/9 hours of
firing (the length of time depends on the type of kiln and the type
of clay used) and the same time again for cooling, the CLAY
becomes POTTERY. As can be seen in the photograph, the clay
changes colour (the degree of redness tone depends on the ferrous
oxides) and becomes SOLID and STRONG. The
clay we use in Deruta takes on a fairly pale pink colour which we
call BISCUIT.
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