Bill and Chris Gold on sat 14 sep 02
Learned sooooo much from that book, but a frustrating problem. I made a
test batch of bone and spearmint, fired and slow cooled as suggested. The
test cylinders turned out great, beautiful with no glaze faults. Made up
larger batches (3000 grams dry ingredients ea). Now, I'm applying the
glaze to the same thickness, using the same chemicals as the test batch,
firing to the same schedule on the same clay body bisqued to 04. The bone
and spearmint blistered badly, so the next glaze firing I applied them very
thin. The bone is ok, but the spearmint is still blistering and the color
is much more olive than the test batch. My other glazes in the same firing
are fine. I'm using standard 101 clay. Could I have made a mistake in
mixing my glaze? If so, should I chuck the whole batch, or try diluting
the batch with another mixed up batch? What could my mistake have
been? Too much Copper carbonate? Not enough or too much of something
else? Any suggestion would be appreciated.
Thanks!
Chris Gold in York, PA where everything is dry, dry, dry...
John Hesselberth on sat 14 sep 02
Hi Chris,
The "olive Spearmint" is probably from your rutile. There are lots of
different grades of rutile available to potters, unfortunately.
Substitute the same of amount of TiO2 and see if the color is closer.
I've never seen blistering on this glaze though. Are you sure of your
firing temperature? Are you using large witness cones in the kiln? If
it is not firing temperature then I would mix another (smaller) batch --
no sense making a large batch again until you are sure.
Regards,
John
On Saturday, September 14, 2002, at 12:23 PM, Bill and Chris Gold wrote:
> The bone is ok, but the spearmint is still blistering and the color
> is much more olive than the test batch.
Frog Pond Pottery
PO Box 88
Pocopson, PA 19366
Fax or phone: 610-388-1254
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