Ivor and Olive Lewis on sun 2 nov 08
Dear Deborah Thuman,
If your clay is being made from dry stock and a variety of ingredients
(...made from scratch...) it is possible one of the substances
contains residues of organic contamination. It may be that the rate
of firing is inadequate to allow this to burn away and should be
reduced to allow time for the reaction to be completed.
My suggestion would be to reduce the rate of heating between 500 deg C
(932 F) and 900 deg C (1650 F).
Graduate students should have sufficient experience to sort this
problem.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
In class, we're using the same ^04 clay, and the same commercial ^04
clear glaze as in past years. The clay is made from scratch. The
firing is to ^03 as in past years. In past years, there was no problem
with the glaze. This year, we've got bubbles in everything. Nasty,
ugly bubbles.
What would cause bubbles to form? There are new kilns and some of the
grad students are using rapid firing. I've been doing my own glaze
firing, ^04 and a slow firing. Even in my firings there are bubbles
although not as many and the bubbles are smaller.
| |
|
