It
is worth thinking about how fast you fire pieces, especially where your current
working temperature and rates of advance are giving difficulties. One common difficulty is where opalescent
glass picks up kiln wash or fibre paper and partially incorporates it,
requiring a lot of work to remove it.
At
higher temperatures opalescent glass seems to incorporate some of the
separator, especially near the edges. It
does not seem to matter whether kiln wash or fibre papers are used – there is frequently
a little pick up.
The
difficulty is achieving the profile you want without the higher
temperatures. This is where heat work concepts can assist. Glass reacts to the heat applied, rather than
simply the temperature. Heat is a
combination of time and temperature.
Rapid rates of advance require higher temperatures than slow rates of
advance to achieve the same effect.
These
facts should make you consider slower rates of advance to achieve the work at a
lower temperature and so pick up less of the separators. Perhaps you could consider a rate of advance
of 150°C or 200°C instead of 330°C once you have passed the bubble squeeze
temperature. This would allow you to
have a full fuse at ca. 800°C or even a little lower instead of 816°C (for Bullseye). You will need to observe to find what is the
appropriate temperature for the effect you want. This will apply both with different rates of
advance and with different lay-ups.
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