J Adams on tue 27 aug 96
I have a glaze that I really love, but it craters on certain clays. It
looks like overfiring and when I reduce the temperature, it seems to
eliminate the problem, but only on certain clays. I use several types of
clay, but they are all stoneware that are advertised as maturing at Cone 4
- 8.
I realize glazes react differently on different clays, but why would the
glaze seem overfired on one type of clay and be fine on another in the same
firing? In the future I plan to just use the clay that glaze seems to
"like", but I am curious. TIA
J. Adams
William R McKinney on wed 28 aug 96
I have recently tried to connect to the SDSU Glazebase glaze database
available on the internet. However, when I tried to search for some
glazes, few or none came up. Finally, I did a global search, which
resulted in about 10 cone 10 glaze recipes, all dating from June, 1996.
Did I
dial into the wrong location, or is this database just beginning and very
thin? If the former, what is the correct address to this database? Is
there another online glaze database that would be more helpful? In
advance, thanks for any help.
Rick McKinney
Dept of History
University of Minnesota
Terrance Lazaroff on fri 30 aug 96
Could be your clay has a lot of material that burns our at higher
temperatures this in turn causes Gas that becomes trapped under your glaze.
Try soaking, or higher bisque temp. Also you did not mention if you fired
reduction. This could make a diff. I recently fired a glaze very well in
oxidation, but when I fired the same clay and glaze in a gas kiln in
oxidation I had blisters. I then remembered that the gas kiln never really
fires oxidation as when temps are being increased there is always a bit of
reduction going to happen.
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