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Mica Firing Temperatures
Click
here for basic information on mica.
Mica powder can be used as an inclusion or it can
be applied directly on top of a sheet of glass. But whichever
way it's used, one thing to realize is that mica behaves very
differently when fired to different temperatures. Here's a
brief guide to how mica behaves in the kiln, beginning with uncapped
mica that has been airbrushed, sifted, or painted onto the glass:
At temperatures below around 1350F (730C),
mica does not stick to the glass very well. To get good
adhesion, the lowest temperature that will work consistently is
around 1380F (750C).
Firing in the range from 1400 to 1450F (760
to 788C), micas are fairly stable. They cannot easily be
scratched from the top surface of the glass, and can be used as
tiles, platters, etc.
However, if you go much higher the mica
starts to lose its stability. By 1500F (815 C) it begins to
burn off and higher temperatures can cause virtually all of the mica
to disappear.
Capping micas will help them reach higher
temperatures than 1500F, but even capped micas can become lighter if
soaked for a long time at 1500F or fired to higher temperatures.
Stay tuned for future tips,
which will discuss more ways to use mica in fused glass.
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Copyright 2005 Brad Walker.
All rights reserved.
Thanks to Avery Anderson and
other board posters for many of the mica tips.
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