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Parent Category: Technical Articles from Journal Back Copies

Category: Technical Articles 2009

Ellen Goldman

A Guild member who had bought two opaque pink Thompson enamels from me (# 10705 and 1708) , wrote to say that she had had great difficulties when she tried to use these colours on PMC-3. She asked me what might have gone wrong.

In answer, I ran some tests for her. I made some small tabs finished them (wire brush and burnisher) and applied the enamel. I divided the pieces of PMC into 2 halves and applied flux # 2020 on one half. After firing (740°C in my kiln)* I found both colours O.K., with - as well as without a base coat of flux. Trying to find out what might have gone wrong I turned the temperature up to 780 °C and saw that the colours had changed drastically. So heat must be a factor. I had the same results when my kiln was set at 760°C and at 750° C. I tried to put an extra layer of the enamel on the last two sample pieces. On the piece I had fired at 750° C the discoloration became less but it was not yet what it should be. My first conclusion was, therefore, that the temperature is the most important factor.

• Not everyone has a calibrated kiln temperature, so it is possible that - even if your kiln shows a temperature of 740° C - the temperature is too high.

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