Joan & Tom Woodward on fri 10 sep 99
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Why do glazes react differently on different surfaces of the same pot? The =
pots
giving rise to this question at the moment are lovely on the inside and =
holey on
the outside. The clay is WMP cone 4-6 from Clay Art Center. Oxidation =
firing.
Looking forward to learning more=21
Joan
Dannon Rhudy on sat 11 sep 99
At 03:17 PM 9/10/99 EDT, you wrote:
>----------------------------Original message----------------------------
>-------------------
>Why do glazes react differently on different surfaces of the same pot?
....lovely on the inside and holey on the outside. ....
-------------------------------------------
The odds are good - VERY good- that the reasons for the smooth
interior is that it stays hot longer INSIDE the pot, and any bubbles
have more time to heal. Maybe you need to hold your kiln at temp
for a bit, to give the outsides time to do the same. And/or - perhaps
you are bisquing too quickly, which could leave various substances
in the clay, which then would have to exit THROUGH your glazes.
But I'm betting on the first possibility.
Regards,
Dannon Rhudy
potter@koyote.com
Frank M. Gaydos on sun 12 sep 99
Joan,
A glaze on the inside is flowing into itself and on the outside away from
itself if we are talking about a bowl form here. Also, the outside is more
subject to the kiln environment and might react differently or, if you trim
the pot and did not press the grog back into the clay, that could cause
pinholing also. Sometimes the way you glaze your pot (Pouring) might cause
it to be thicker inside.
Hope that helps...
Frank Gaydos
-------------------------------------Question-------------------------------
----------------------------------------
Why do glazes react differently on different surfaces of the same pot? The
pots
giving rise to this question at the moment are lovely on the inside and
holey on
the outside. The clay is WMP cone 4-6 from Clay Art Center. Oxidation
firing.
Looking forward to learning more!
Joan
Bill Williams on sun 12 sep 99
I don't know the scientific answer to that, but I'll tell you what I have
found in my own unscientific way. I was having a lot of trouble with pin
holes. I would also get a smooth surface on the inside, but not on the
outside. I started firing my greenware at cone 04 instead of 06. I also
started wetting my pieces before I put the glaze on. I always sort of
sponged them off before, but not I actually put them under the faucet and
run water inside and out. This has stopped my problem for the most part.
What I think happens is that the pot starts to absorb moisture when you
start applying the glaze and thus makes pin holes. If the pot is already
wet, the hole are already plugged up, so to speak. Anyway, for whatever
reason, it worked for me. Connie
-----Original Message-----
From: Joan & Tom Woodward
To: CLAYART@LSV.UKY.EDU
Date: Friday, September 10, 1999 2:18 PM
Subject: pin holes
----------------------------Original message----------------------------
-------------------
Why do glazes react differently on different surfaces of the same pot? The
pots
giving rise to this question at the moment are lovely on the inside and
holey on
the outside. The clay is WMP cone 4-6 from Clay Art Center. Oxidation
firing.
Looking forward to learning more!
Joan
Donn Buchfinck on sun 12 sep 99
OK people
this is why the inside of pots look better sometimes than the outside
it has to do with the firing atmosphere
if you reduce the kiln hard during firing it is a good bet that the outside
glaze will be reduced hard, but the interior will have a neutral atmosphere,
thus giving a beautiful glaze on the inside of the pot
even when firing the gasses flow through a kiln like a wind striking to pots
in different ways, but the inside always has protection
shinos and copper reds I have seen this happen to
mainly in the inside of lidded jars that have a lid
I think it is just too easy to overreduce at the end of the firing, drawing
gasses out of the glaze and clay and then shutting off the kiln, not giving
enough time for the glazes to heal.
Everyone needs to find out how to fire their own equipment, and glazes, I
cannot show you how to speak a language, but I can help you with concepts.
Good luck
Donn Buchfinck
San francisco
Ron Roy on tue 14 sep 99
It is usually the case that glazes are "better" looking inside pots. It
must be true that the glaze cools more slowley on the inside and perhaps
that is the reason.
There are ways to fix a a glaze to get rid of pinholes of course - the
simple way is to take out some clay so the glaze is less viscous - best to
do it using calclation - easier to keep the same look that way.
Soaking at the end of a firing is always a good idea as well.
I think the glaze is the problem here - not the clay - or the bisque firing.
RR
>----------------------------Original message----------------------------
>-------------------
>Why do glazes react differently on different surfaces of the same pot?
>The pots
>giving rise to this question at the moment are lovely on the inside and
>holey on
>the outside. The clay is WMP cone 4-6 from Clay Art Center. Oxidation firing.
>Looking forward to learning more!
>
>Joan
Ron Roy
93 Pegasus Trail
Scarborough
Ontario, Canada
M1G 3N8
Evenings 416-439-2621
Fax 416-438-7849
Gavin Stairs on wed 15 sep 99
At 04:43 PM 9/14/99 -0400, Ron Roy wrote:
>----------------------------Original message----------------------------
>It is usually the case that glazes are "better" looking inside pots. It
>must be true that the glaze cools more slowly on the inside and perhaps
>that is the reason.
It is always the case that a cavity will cool more slowly than an outside
surface. Simple thermodynamics: the cavity has to radiate heat out the
spout, so to speak, while the outside can radiate everywhere. Bottoms are
like cavities, and so are outsides which are shielded by an adjacent
surface, like another pot. So, in a close packed kiln, everything will
cool a bit slower, except the outsides of the pots on the outside, etc.
And the insides will cool slowest. So, if your pinholes come from fast
cooling, look for them to be on the outsides, near the wall, or near any
open vent, like a spyhole.
Gavin
GEORGE HILL on sat 25 sep 99
I would like to know the glaze you are using? Is it from Clay Art
Center, another source, or one you made yourself?
Joan & Tom Woodward wrote:
>
> ----------------------------Original message----------------------------
> -------------------
> Why do glazes react differently on different surfaces of the same pot? The po
> giving rise to this question at the moment are lovely on the inside and holey
> the outside. The clay is WMP cone 4-6 from Clay Art Center. Oxidation firing
> Looking forward to learning more!
>
> Joan
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