Saturday, January 14, 2006

Spoke with Vicki About Glazes

I finally had a chance to talk with Vicki, my pottery instructor down in Atlanta about our glaze and raku woes.

We first verified that the Floating Blue recipe that I have is correct. It in an old composition book, and one of the components of the recipe was added in a different color ink than the rest. It turns out that the recipe was spot on.

From the description that I gave her, she is guessing that the Floating Blue was overfired. This could be caused by turning the kiln up too fast; the rate at which the temperature increased in the kiln at full power caused the temperature to soar past cone 6, before the cone had a chance to bend.

Our kiln has three banks of kiln elements, and each has a rotary switch with Off-Lo-Med-Hi settings. According to our kiln log, we went from all of the dials at Lo to Medium, and then an hour later moved them all to Hi. Next time, we plan to turn the knobs to high one at a time, so will go from all medium to all high in three hours instead of one hour.

A pyrometer would help as well. We never found the one that I bought with the gas kiln, its in a box someplace, but we were thinking of acquiring a digital pyrometer for raku firing.

Vicki also agrees with me that firing the raku kiln in reduction was a bad idea for our glazes.


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