Conventional
advice is to begin glazing with commercial mixes and that is the approach I
took. By this time I’d also pretty much committed to one type of stoneware clay
as the best for the next stage of exploration.
Now an electrical
kiln operates in an atmosphere where the oxygen in the heated air is at normal
levels (oxidising) and so various components of a glaze when in molten form tend
to be relatively more stable than the alternative. In a fired kiln (timber or
gas) the oxygen is consumed and the atmosphere in the kiln is a reducing one –
which tends to extract the oxygen out of many glaze components which are
basically metallic oxides. This can cause interesting colour responses. With
modern analytical tools and a thorough understanding of the interaction between
the key components it is possible to achieve just as interesting results in an
oxidising atmosphere.
Glazes are
amazing mixtures of clay, minerals, silica and metallic oxides nearly all of
which have individual melting temperatures well beyond the maturity or
vitrification temperature of clay. The really interesting thing is that when
you mix these powders together, they then melt at a temperature below the
vitrification temperature. These eutectic compositions have been the subject of
plenty of scientific investigation and are well understood. So the ancients did
pretty well to get started on that path in the 8th or 9th
century BC.
That makes me a
late starter and here is my first effort
at testing variously sourced glaze recipes. At this point I’m principally
chasing glaze formulations which have a matte or preferably satin finish. I’m
not keen on the shine of high gloss and the satin surface is just as easy to
keep clean. That said there are some pots which look quite good in gloss. It’s
an interesting call to make.
Just for fun I
thought I’d post my winged griffin. Modelled on an old European stove tile - clear
Italian Green gloss over terracotta.
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Happy to hear your advice, feedback or questions