"Rafael Molina-Rodriguez (Rafael Molina-Rodriguez)" on sun 26 jan 97
Jennifer :
The glazes may not be the problem. Two possibilities for the cracking
may be the claybody and/or the firing cycle. If you are using a dark
stoneware and reducing too early and too long your work may be getting
carbon core also known as black core. This results in extreme
brittleness and cracking.
Check your claybody recipe. Stoneware clays that have iron added in
the form of iron oxide, redart, etc.,... are susceptible to this problem.
What kind of ball clay are you using? In my experience, OM4 was the
type of ball clay, for a claybody, that gave me the most problems.
Apparently, there is more iron present in this ball clay than others. Try
other ball clays i.e. #1sgp or spinks.
The firing cycle is another area you should examine. Specifically, the
reducing part of the cycle. When, how much, and for how long you
reduce can encourage black coring and the subsequent problems of
brittleness and cracking.
If you're using a dark stoneware don't reduce below ^ 05. I got this info
from an article in Studio Potter written by Michael Cardew.
When placing the kiln in reduction, do so moderately. It's not necessary
to have lots of back pressure, yellow flames, and smoke/soot coming off
of the flame tips. After approximately 30 minutes adjust kiln for a light
reduction and fire to maturing temperature.
Good luck.
Rafael Molina-Rodriguez
Cedar Valley College
RMR3431@DCCCD.EDU
(972) 860-8046
>>> Jennifer Rhinesmith 01/25/97 11:08am
>>>
----------------------------Original message----------------------------
HELP!!! I do cone 9-10 reduction firing and there have been some
problems. I have been experimenting with some different glaze recipies
and have had little sucsess. I have been using V.C.'s Wild Wonder and
Ned Coleman's Purple, two glazes that I really love. Everything that I
put them on comes out broken. I mix up my own clay body, for the most
part. Does anyone use these glazes on a basic stoneware body and if
so do
you have these problems? I have been told that there is a glaze fit
problem, so can anyone tell me how to remedy this problem. Last
semester
I had a 30% loss, and that really hurt. Any info. on this would be
greatly appreciated. Thank You Jennifer in Alpine
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