Gail Dapogny on tue 16 apr 02
I am perplexed by something that keeps happening to me. I am using a lot
of porcelain (grolleg) and the body seems pretty tolerant if I don't
mistreat it by drying too quickly, etc.
HOWEVER....I too often get very fine cracks here and there in the fired
glazes, maybe a couple of inches long. These minute cracks never go though
the body. I do a lot of sprayed overlapping glazes but the glaze cracking
does not seem to occur consistently in any one type of area such as in the
thicker areas. I sieve my glazes each time I use them, and finger-smooth
any areas that are not completely smooth.It does seem to happen in quite
glossy glazes.
The problem is driving me nuts, and I could not find any references in our
archives.
Sorry, don't happen to have the porcelain recipe at hand just now. If
anyone thinks it is a body problem, I will publish it. Any help
appreciated!!
---Gail
Gail Dapogny
1154 Olden Road
Ann Arbor, MI 48103-3005
(734) 665-9816
gdapogny@umich.edu
http://www.silverhawk.com/ex99/dapogny (single historical photo - no longer
registered with Silverhawk)
David Hewitt on wed 17 apr 02
Gail,
It sounds as if your glaze does not fit your porcelain body well enough.
Porcelain has a relatively low coefficient of expansion when compared
with that of stoneware so, while a glaze may not craze on stoneware it
may on porcelain.
For a general article on the problem you may like to look at my web site
under Pottery Techniques / Calculating Crazing.
http://www.dhpot.demon.co.uk
If I can help further please come back to me.
David
In message , Gail Dapogny writes
>I am perplexed by something that keeps happening to me. I am using a lot
>of porcelain (grolleg) and the body seems pretty tolerant if I don't
>mistreat it by drying too quickly, etc.
>HOWEVER....I too often get very fine cracks here and there in the fired
>glazes, maybe a couple of inches long. These minute cracks never go thoug=
>h
>the body. I do a lot of sprayed overlapping glazes but the glaze crackin=
>g
>does not seem to occur consistently in any one type of area such as in th=
>e
>thicker areas. I sieve my glazes each time I use them, and finger-smooth
>any areas that are not completely smooth.It does seem to happen in quite
>glossy glazes.
>The problem is driving me nuts, and I could not find any references in ou=
>r
>archives.
>
>Sorry, don't happen to have the porcelain recipe at hand just now. If
>anyone thinks it is a body problem, I will publish it. Any help
>appreciated!!
>---Gail
>
>Gail Dapogny
>1154 Olden Road
>Ann Arbor, MI 48103-3005
>(734) 665-9816
>gdapogny@umich.edu
>http://www.silverhawk.com/ex99/dapogny (single historical photo - no long=
>er
>registered with Silverhawk)
--
David Hewitt
David Hewitt Pottery ,
7 Fairfield Road, Caerleon, Newport,
South Wales, NP18 3DQ, UK. Tel:- +44 (0) 1633 420647
FAX:- +44 (0) 870 1617274
Web site http://www.dhpot.demon.co.uk
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