Paul B on sun 20 nov 05
Are there any known problems associated with hawthorne bond fireclay that
cause glaze defects such as blisters?
I get some large blisters and bubbles that show up from time to time on the
glaze surface that i never got with the commerical body i used up until
about 2 years ago (which was made by standard ceramics, the "153"
stoneware).
I have varied my stoneware formula a lot, taking out things like OM-4 and
goldart, both of which i have heard bad things about, but it did not have
much affect. I thought for sure it had to do with one of those two - i used
old hickory #5 instead of OM-4 for a while with no difference. The blisters
tend to come and go, showing up more in some glazes than others, especially
when applied thick, but i still see traces of them on other glazes that go
on thin sometimes.
I do a long electric bisque to cone 04, pots stacked loose enough for
ventilation; and during the glaze firing i soak as long as possible without
overfiring the glazes.
It looks like a large bubble burst on the surface of the glaze - sometimes
it smooths out and others leaves a sharp edge. I have tested the body and
know that it is not overfired.
If it has to do with the materials in the body it could only be the
hawthorne bond (35 mesh) since i have tried mixing it without the other
clays except EPK but i know that is not the problem.
Any ideas here?
thanks,
Paul
Linda Blossom on mon 21 nov 05
My clay body is 35% Hawthorn Bond and I single fire and have never had a
problem with blistering. I fire both electric and gas firings. I fire many
glazes, everywhere from cone 6 to 10 without problems.
Linda
Ithaca, NY
Are there any known problems associated with hawthorne bond fireclay that
cause glaze defects such as blisters?
I get some large blisters and bubbles that show up from time to time on the
glaze surface that i never got with the commerical body i used up until
about 2 years ago (which was made by standard ceramics, the "153"
stoneware).
I have varied my stoneware formula a lot, taking out things like OM-4 and
goldart, both of which i have heard bad things about, but it did not have
much affect. I thought for sure it had to do with one of those two - i used
old hickory #5 instead of OM-4 for a while with no difference. The blisters
tend to come and go, showing up more in some glazes than others, especially
when applied thick, but i still see traces of them on other glazes that go
on thin sometimes.
I do a long electric bisque to cone 04, pots stacked loose enough for
ventilation; and during the glaze firing i soak as long as possible without
overfiring the glazes.
It looks like a large bubble burst on the surface of the glaze - sometimes
it smooths out and others leaves a sharp edge. I have tested the body and
know that it is not overfired.
If it has to do with the materials in the body it could only be the
hawthorne bond (35 mesh) since i have tried mixing it without the other
clays except EPK but i know that is not the problem.
Any ideas here?
thanks,
Paul
Louis Katz on mon 21 nov 05
We have been having intermittent problems here as well. WE use a
mixture of hawbond and Greenstripe fireclay as our fireclay in our
stoneware. We also have been having a bit of trouble with things
burning out leaving holes. The Hawthorne is the main suspect right now.
I would first make sure you are oxidizing in your glaze kiln at least
until cone 012.
On the other hand.
If that does not help you might try a short period of reduction below
cone 012 followed by oxidation.
Some compounds do not volatize easily in in oxidation below cone 1 it
seems. This is a theory anyways. Some carbonates are given off later,
and some sulphur compounds hang on until right close to cone ten it
seems.
Years ago Richard Burkett told me that some sulphur compounds
volitalize sooner if you reduce them at red heat. This seemed born out
by things we tried.
I am considering going to a clay without any hawthorne next semester.
My good throwers prefer a little hawthorne in their clay but I am tire
of getting junk. I am also (horror) thinking of blunging the Haw Bond
and mixing it with the other ingredients after seiving wet ( What a
pain). This will require a complete change of tact in the studio, with
more selection happening before firing.
I have students blunging porcelain and drying it in frames. The are
much more careful with the labor intensive clay and changing the whole
studio to this sort of operation might make for better pots without me
resorting "you have to slake this" routine. If anyone knows of a good
filterpress for sale, I might be wiling to trade a dough mixer for it.
Louis
***Louisiana Mississippi Ceramics and Potters Information page*****
http://falcon.tamucc.edu/wiki/Katz/LAMIPotters
On Nov 20, 2005, at 7:44 PM, Paul B wrote:
> Are there any known problems associated with hawthorne bond fireclay
> that
> cause glaze defects such as blisters?
> I get some large blisters and bubbles that show up from time to time
> on the
> glaze surface that i never got with the commerical body i used up until
> about 2 years ago (which was made by standard ceramics, the "153"
> stoneware).
> I have varied my stoneware formula a lot, taking out things like OM-4
> and
> goldart, both of which i have heard bad things about, but it did not
> have
> much affect. I thought for sure it had to do with one of those two - i
> used
> old hickory #5 instead of OM-4 for a while with no difference. The
> blisters
> tend to come and go, showing up more in some glazes than others,
> especially
> when applied thick, but i still see traces of them on other glazes
> that go
> on thin sometimes.
> I do a long electric bisque to cone 04, pots stacked loose enough for
> ventilation; and during the glaze firing i soak as long as possible
> without
> overfiring the glazes.
> It looks like a large bubble burst on the surface of the glaze -
> sometimes
> it smooths out and others leaves a sharp edge. I have tested the body
> and
> know that it is not overfired.
> If it has to do with the materials in the body it could only be the
> hawthorne bond (35 mesh) since i have tried mixing it without the other
> clays except EPK but i know that is not the problem.
> Any ideas here?
> thanks,
> Paul
>
> _______________________________________________________________________
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> Send postings to clayart@lsv.ceramics.org
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>
Kathi LeSueur on mon 21 nov 05
Paul B wrote:
>Are there any known problems associated with hawthorne bond fireclay that
>cause glaze defects such as blisters?
>I get some large blisters and bubbles that show up from time to time on the
>glaze surface that i never got with the commerical body i used up until
>about 2 years ago (which was made by standard ceramics, the "153"
>stoneware).>>
>
My clay supplier substituted Hawthorne in an attempt to get rid of a
flaw with one of my glazes. I still had pitting, but worse, I had lots
of cracking. In the end I had him go back to the original formula and
use a totally different clay for that glaze.
Kathi
Joe Orosco on fri 25 nov 05
Try levigating the clay first that settles many of the impurities to the bottom of the container
-----Original Message-----
From: Kathi LeSueur
Sent: Nov 21, 2005 2:20 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: PROBLEMS ASSOCIATED WITH HAWTHORNE BOND FIRECLAY?
Paul B wrote:
>Are there any known problems associated with hawthorne bond fireclay that
>cause glaze defects such as blisters?
>I get some large blisters and bubbles that show up from time to time on the
>glaze surface that i never got with the commerical body i used up until
>about 2 years ago (which was made by standard ceramics, the "153"
>stoneware).>>
>
My clay supplier substituted Hawthorne in an attempt to get rid of a
flaw with one of my glazes. I still had pitting, but worse, I had lots
of cracking. In the end I had him go back to the original formula and
use a totally different clay for that glaze.
Kathi
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You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/
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Nancy Marenger on wed 30 nov 05
Linda,
I'm totally new to this site, but I've been told that you are the QUEEN of
sinks. Can you give me the best way to make a sink with the least amount
of waste, warpage, and the most success? What clay body is the best? What
is with "throwing a pot upside down"?9my mind only visualizes some pretty
bizare stuff!) I have a fine arts background from university, have my own
wheel and kiln, and after many years of just teaching at the primary
level, am trying to get back into my passion. How big should I make the
drain hole? Is there a good book or video you would suggest?
Thanks for letting me ramble on.
Nancy
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