Cat Jarosz on tue 2 jan 01
Hi Sue .... alot of pin hole problems can be cured with correct
bisque... I do not know what temp a cone 5-6 bisque is but for cone 9-10
its generally 04 ... by soaking at 016 for 1 hr and at 04 for 1 hr at
the end it has cured alot of pin hole problems... Hope this helps some...
Cat
Cindy Strnad on tue 2 jan 01
Hi, Sue.
This isn't really a very good glaze--not unless you mean to use it for
purely decorative purposes. I'm sure it's very pretty, though. Perhaps you
should consider the "craters" as a part of the ambience of this particular
glaze. It's extremely low on both alumina and silica, and may not be able to
hold on to its colorants under the onslaught of a mild acid. Try storing a
bit of vinegar in a test piece for a couple of hours and see what happens.
Here's a nice red which I enjoy. It came from Clayart some time ago. If you
have Gerstley on hand and don't mind using it, you might like this glaze. It
won't have the interesting texture of your glaze, but it is stable and will
give you an excellent red. To get the red color, you'll want a medium-thick
application and a slow cool. If you can't control the cooling rate of your
kiln, try re-firing the pieces in your next bisque load--this will bring out
the redness.
Red Brown ^6
Cheryl Litman
SILICA 29
EPK KAOLIN 5
CUSTER FELDSPAR 20
TALC 15
GERSTLEY BORATE 32
IRON OXIDE RED 15
I hope this is of help to you.
Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
earthenv@gwtc.net
http://www.earthenvesselssd.com
Craig Martell on tue 2 jan 01
Sue sez:
>I am having lots of trouble with pin holes in an Iron Glaze I took from
>Ceramics Monthly. If there are any suggestions I would be grateful since the
>glaze is beautiful except for the planet Mercury type craters.
>Iron Red Glaze (cone 5-6) Ceramics Monthly, April 1990
>Gerstly Borate-54.88
>Talc-14.63
>Flint-30.49
Hi:
Sorry to put forth such a negative response about your glaze but it's way
outta whack. For a cone 5-6 glaze there's only one oxide out of 5 that is
within limits. There's virtually no alumina in the glaze and too little
silica. About 3 times the suggested amount of boron.
I think it would take a major overhaul to make this one trouble free. As
it stands now, this glaze is not a balanced, durable glass and definitely
shouldn't be used on food contact surfaces.
I think I would start over.
regards, Craig Martell in Oregon
Sue Rolf on tue 2 jan 01
I am having lots of trouble with pin holes in an Iron Glaze I took from
Ceramics Monthly. If there are any suggestions I would be grateful since the
glaze is beautiful except for the planet Mercury type craters.
Iron Red Glaze (cone 5-6) Ceramics Monthly, April 1990
Gerstly Borate-54.88
Talc-14.63
Flint-30.49
I have tried longer, hotter soaks, and three different base glazes (no holes
but uglee). I have added 5% Zinc Oxide and 10% Zinc Oxide(Bad idea!)
many thanks, Sue Rolf
James L Bowen on thu 4 jan 01
I have a bowl glazed with this glaze that gets
used everyday. It gets used with acidic foods
DAILY. Lots of tomatoes and chiles It shows no
signs of color change or loss of gloss. It is
very durable. I bought it two years ago at
Cherry Creek from Dave Yungner of Minnesota. See
page 26 Jan 2001 Ceramics monthly for a pot with
this glaze.
John Hesselberth on fri 5 jan 01
This thread is beginning to get interesting. I certainly agree with
Craig and Cindy that this glaze looks terrible by analysis. But daily
use with acidic foods is a hard data point to argue against. The
discrepancy could be caused by one of at least two things:
1. If you use the GB analysis from 9/97, that I think most of us use,
this glaze is very low in silica (1.77) and it has almost no alumina
(0.021). On the other hand, if you use the 1999 analysis for GB, the
composition looks entirely different. Silica is up to 2.4. Alumina is
still very low at 0.11, but at least there is some. Now the question is
which analysis is the appropriate one to use. No one knows. Thank
heavens GB is disappearing from the scene!
2. Another reason this glaze might be giving James the results he is
getting is that iron is pretty easy to keep in a glaze. If the Yunger
has some GB that meets the 1999 analysis he might get by with this. But
don't change batches of GB or watch out!!
A question for the original questioner, Sue Rolf. Why bother to try to
correct a glaze where the prime ingredient is no longer available (and if
it were still available is so variable in composition) ? I'd recommend
you give Cheryl's recipe (in Cindy's message) and try and see if it will
work for you.
Regards, John
James L Bowen wrote:
>I have a bowl glazed with this glaze that gets
>used everyday. It gets used with acidic foods
>DAILY. Lots of tomatoes and chiles It shows no
>signs of color change or loss of gloss. It is
>very durable. I bought it two years ago at
>Cherry Creek from Dave Yungner of Minnesota. See
>page 26 Jan 2001 Ceramics monthly for a pot with
>this glaze.
>
"The life so short, the craft so long to learn." Hippocrates, 5th cent.
B.C.
Sue Rolf on sat 6 jan 01
Hi Cindy,
Thanks for the glaze, I'll give it a try. I'm going to try to substitute
the Gerstly Borate. If I have any luck I'll let you know. If you have a
successful sub. please feel free to pass it on.
Thanks,
Sue Rolf
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