Teresa Testa on sun 14 dec 03
I am at my wits end here. I am using a single fire glaze recipe that is
60%Custer Spar. I am having a lot of trouble with bloating and pinholing. Here
is the firing schedule I use.
150-185 hold 1 hr
30-215 hold 1 hr
150-1060 hold 1 hr
250-2100 hold 1 hr
108-2345 hold 20 minutes
9999-1900 hold 30 minutes
9999-110 hold 1 hr
Most of my single fire work comes out with bloating, pinholing and/or
craters. I fire my 04 bisque in the same firing and everything is fine. I used the
same clay for the bisque and the single fire, so it is not the clay. The colors
also seem to wash out of the single fire glazes. They are not consistent
when I try to reproduce them. I have measured the glazes very carefully so I
don't think it is that. My work is very thick in some areas and I need to fire
up slow and cool off slow. I am ready to give up on this single fire glaze
business and go back to bisqueing all my work before glazing.
Did I mention I use Coleman Porcelain?
All my glazes are sprayed on.
Thanks for any help.
Teresa
Windancer Studio
Las Vegas, NV
PS. When I try to refire my work the colors come out suo ugly. They don't
look anything like the colors from the first firing.
Tony Ferguson on sun 14 dec 03
Teresa,
You are firing too fast for sure. It appears you are not allowing the
gasses to get out of the clay body. The particular glaze you are using
could also, because of its make up, not handle such a fast firing. Your
temperature numbers are they accurate?
Let your kiln take 12-15 hours from start to finish and see what happens.
When I would fire a gas kiln, I would load, and pilot for 2 hours, close the
door, do a few turn ups that would nearly allow red heat by the next morning
(010 ish. I would set early reduction, and do turn ups through out the day
and fire it off in the early or sometimes late evening. From the time of
red heat, it would take 6 to 8 or even 10 hours to fire it off to cone 10.
I was firing reduction of course and a car kiln, so it shouldn't take you as
long with an electric and smaller load.
Send me your glaze recipe and I will try to comment based on what I have
experienced.
Crank that baby up! Go slower. I lost many many loads till I figured it
out. Perhaps I can save you some time, effort, and disappointment.
Thank you.
Tony Ferguson
On Lake Superior, where the sky meets the Lake
Custom & Manufactured Kiln Design
Stoneware, Porcelain, Raku and more
by Coleman, Ferguson, Winchester...
http://www.aquariusartgallery.com
218-727-6339
315 N. Lake Ave
Apt 312
Duluth, MN 55806
From: "Teresa Testa"
To:
Sent: Sunday, December 14, 2003 9:38 AM
Subject: Blaoting & Pinholing Single fire glazes
> I am at my wits end here. I am using a single fire glaze recipe that is
> 60%Custer Spar. I am having a lot of trouble with bloating and pinholing.
Here
> is the firing schedule I use.
> 150-185 hold 1 hr
>
> 30-215 hold 1 hr
>
> 150-1060 hold 1 hr
>
> 250-2100 hold 1 hr
>
> 108-2345 hold 20 minutes
>
> 9999-1900 hold 30 minutes
>
> 9999-110 hold 1 hr
>
>
> Most of my single fire work comes out with bloating, pinholing and/or
> craters. I fire my 04 bisque in the same firing and everything is fine. I
used the
> same clay for the bisque and the single fire, so it is not the clay. The
colors
> also seem to wash out of the single fire glazes. They are not consistent
> when I try to reproduce them. I have measured the glazes very carefully
so I
> don't think it is that. My work is very thick in some areas and I need to
fire
> up slow and cool off slow. I am ready to give up on this single fire
glaze
> business and go back to bisqueing all my work before glazing.
>
> Did I mention I use Coleman Porcelain?
>
> All my glazes are sprayed on.
>
> Thanks for any help.
>
> Teresa
>
> Windancer Studio
>
> Las Vegas, NV
>
> PS. When I try to refire my work the colors come out suo ugly. They
don't
> look anything like the colors from the first firing.
>
>
____________________________________________________________________________
__
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
>
william schran on sun 14 dec 03
Teresa wrote:>Most of my single fire work comes out with bloating,
pinholing and/or
craters. I fire my 04 bisque in the same firing and everything is
fine. I used the
same clay for the bisque and the single fire, so it is not the clay.<
Ahhh, but it might be the clay. Do you have these problems with
glazes on the pots that were bisque fired? The gases from organic
materials may not have an opportunity to burn out completely before
the glaze begins to sinter/melt, thus trapping the gases under the
glaze later in the firing, especially since the glaze & bisque are
both cone 04. You may also have problems with blistering if you don't
allow for a soak at the end of the firing.
Bill, Fredericksburg, Va where we got 3" of snow last night, followed
today with rain - just plain nasty weather.
Earl Brunner on sun 14 dec 03
Your problem may be in your second and third settings area. Basically
you have to treat single fired work, in the first part of the firing as
if it is a bisque. If you haven't burned out all of the organics before
the glaze begins to melt, then you are trapping carbon and possibly
other gases in the clay, this could be at the root of your pinholing,
and possibly the bloating and craters as well. By bloating, do you mean
large bubbles forming inside the wall of you piece?
Who is making your Coleman Porcelain? In the past a version has been
made by Laguna and one has been made by Aardvark. I'm a little confused
by part of your message, you indicate that you fire your 04 bisque in
the same firing and everything is fine. You fire your 04 bisque to
2345? And it's the same clay? If that's the case, It could still be
the same problem. Your bisque has no glaze on it the first firing and
the organics can outgas ok.
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Teresa
Testa
Sent: Sunday, December 14, 2003 7:38 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Blaoting & Pinholing Single fire glazes
I am at my wits end here. I am using a single fire glaze recipe that is
60%Custer Spar. I am having a lot of trouble with bloating and
pinholing. Here
is the firing schedule I use.
150-185 hold 1 hr
30-215 hold 1 hr
150-1060 hold 1 hr
250-2100 hold 1 hr
108-2345 hold 20 minutes
9999-1900 hold 30 minutes
9999-110 hold 1 hr
Most of my single fire work comes out with bloating, pinholing and/or
craters. I fire my 04 bisque in the same firing and everything is fine.
I used the
same clay for the bisque and the single fire, so it is not the clay. The
colors
also seem to wash out of the single fire glazes. They are not
consistent
when I try to reproduce them. I have measured the glazes very carefully
so I
don't think it is that. My work is very thick in some areas and I need
to fire
up slow and cool off slow. I am ready to give up on this single fire
glaze
business and go back to bisqueing all my work before glazing.
Did I mention I use Coleman Porcelain?
All my glazes are sprayed on.
Thanks for any help.
Teresa
Windancer Studio
Las Vegas, NV
PS. When I try to refire my work the colors come out suo ugly. They
don't
look anything like the colors from the first firing.
________________________________________________________________________
______
Send postings to clayart@lsv.ceramics.org
You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/
Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
Teresa Testa on sun 14 dec 03
Thanks for the tips. I forgot to mention I am firing a 12 cu ft electric.
Ron Roy on thu 18 dec 03
Hi Teresa,
If I could see the recipies of the glazes you are using I might be able to
find some reason - thick clay needs time to get the carbonous material out
and you glazes may be sealing them in - especiall if they work OK on bisque
fired work.
Stephen Hill did a couple of articles on high fire single fire in CM -
January 86 is the only one I can find - but there is another more recent I
think.
RR
>I am at my wits end here. I am using a single fire glaze recipe that is
>60%Custer Spar. I am having a lot of trouble with bloating and pinholing.
>Here
>is the firing schedule I use.
>150-185 hold 1 hr
>
>30-215 hold 1 hr
>
>150-1060 hold 1 hr
>
>250-2100 hold 1 hr
>
>108-2345 hold 20 minutes
>
>9999-1900 hold 30 minutes
>
>9999-110 hold 1 hr
>
>
>Most of my single fire work comes out with bloating, pinholing and/or
>craters. I fire my 04 bisque in the same firing and everything is fine. I
>used the
>same clay for the bisque and the single fire, so it is not the clay. The colors
>also seem to wash out of the single fire glazes. They are not consistent
>when I try to reproduce them. I have measured the glazes very carefully so I
>don't think it is that. My work is very thick in some areas and I need to fire
>up slow and cool off slow. I am ready to give up on this single fire glaze
>business and go back to bisqueing all my work before glazing.
>
> Did I mention I use Coleman Porcelain?
>
>All my glazes are sprayed on.
>
>Thanks for any help.
>
>Teresa
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Jon Pacini on fri 19 dec 03
Greeting All, Hi Teresa--- you wrote-----I am at my wits end here. I am
using a single fire glaze recipe that is
>60%Custer Spar. I am having a lot of trouble with bloating and pinholing.
There is an exellent Book By Dennis Parks on the subject of Once Firing---He
is a master of the technique --it is a great resource. It's titled --- A
Potters Guide to Raw Glazing and Oil Firing---ISBN 0684175630. Try Amazon.
Jon Pacini
Clay Manager
Laguna Clay Co
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