iandol on wed 11 sep 02
Some time ago I brought to the attention of Clayarters the presence of =
bubbles in a series of test recipes which had been fired in a non =
reducing atmosphere. My question concerned the composition of the gas =
which might have been evolved from the materials which had been used in =
these samples.
At that time I put forward the notion that the gas was oxygen and that =
it must have come from residual iron oxide in one or more of the =
compounds which I had used. From memory, the question remained =
unresolved.
A patient wait for the summer CM brought a reward, the article on Oil =
Spot Glazes by John Britt. I followed through to the reference given by =
John Britt for his source, another CM article by Brother Anthony, "The =
Chemistry and Physics of Oil-Spot Glazes". This confirmed my supposition =
that it would be Oxygen which is evolving.
Now, I find the lustre of Oil-Spot a rather delightful adornment on some =
pottery forms and since I have a series of compositions which without =
any addition of iron are prone to evolve the gas which is responsible =
for the pattern of this glaze style I may have a potential breakthrough =
in glaze formulation. I am looking forward to extending trials with =
these recipes.
All of the samples which exhibit the evolution of gas have crazed since =
they were taken from the kiln cold. However, I have already done =
pre-emptive work which solves this and already have a solution for the =
clays on which these glazes might be used.
Best regards to all,
Praying for Peace. I think Nelson Mandela has made a valid point.
Ivor Lewis. Redhill. South Australia.
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