Edward D Cowell on fri 27 feb 98
What are your thoughts on refiring functional cone 10 reduction pots? Are
they weakened and thus more susceptible to cracking, etc.?
Laurie Cowell,
Waterloo, Ontario, Canada
Craig Martell on sun 1 mar 98
At 09:28 AM 2/27/98 EST, Laurie Cowell wrote:
>----------------------------Original message----------------------------
>What are your thoughts on refiring functional cone 10 reduction pots? Are
>they weakened and thus more susceptible to cracking, etc.?
Hi:
If you are talking about refiring to stoneware temps., one problem is the
potential development of cristobalite. This is ongoing and the more you
subject clay to high temps the more cristobalite you may develop. This can
cause the pots to fail due to thermal shock. Cristobalite changes volume at
around 437F. and it's never the same temp. It kinda does what it wants
somewhere around this temp range. Unlike the quartz inversion, which is
more gradual, the cristobalite squeeze is sudden and fast. In short, it's a
bad scene!! I would never refire ovenware, teapots, mugs, etc.
regards, Craig Martell-Oregon
Ron Roy on sun 1 mar 98
It depends - if it's porcelain they might just become over fired. If it is
a white stoneware clay there will probably be some cristobalite - if it's a
brown stoneware clay there will probably be lots more. Cristobalite
production increases with time over 1100C. The more cristobalite present
the more chance pots will crack during the cristobalite inversion which is
in oven temperature range. The other factor is the relative expansion of
each glaze you use.
Also keep in mind - when you refire a piece you are really firing it a cone
higher at least - all that heat work accumulates. You may be able to get
around the over firing part in a cooler part of the kiln - but if there is
cristobalite already in the ware you can expect quite a bit more due to the
2nd firing.
If you do it - at least freeze the pots afterwards to precipitate any
latent fit problems.
>----------------------------Original message----------------------------
>What are your thoughts on refiring functional cone 10 reduction pots? Are
>they weakened and thus more susceptible to cracking, etc.?
>
>Laurie Cowell,
>Waterloo, Ontario, Canada
Ron Roy
93 Pegasus trail
Scarborough Otario
Canada M1G 3N8
Phone: 416-439-2621
Fax: 416-438-7849
Web page: Home page http://digitalfire.com/education/people/ronroy.htm
Jim Bozeman on wed 4 mar 98
---Craig Martell wrote:
>
> ----------------------------Original
message----------------------------
> At 09:28 AM 2/27/98 EST, Laurie Cowell wrote:
> >----------------------------Original
message----------------------------
> >What are your thoughts on refiring functional cone 10 reduction
pots? Are
> >they weakened and thus more susceptible to cracking, etc.?
>
> Hi:
>
> If you are talking about refiring to stoneware temps., one problem
is the
> potential development of cristobalite. This is ongoing and the more
you
> subject clay to high temps the more cristobalite you may develop.
This can
> cause the pots to fail due to thermal shock. Cristobalite changes
volume at
> around 437F. and it's never the same temp. It kinda does what it
wants
> somewhere around this temp range. Unlike the quartz inversion,
which is
> more gradual, the cristobalite squeeze is sudden and fast. In
short, it's a
> bad scene!! I would never refire ovenware, teapots, mugs, etc.
>
> regards, Craig Martell-Oregon
>
I have reglazed and refired my stoneware pots numerous times and have
never had any problems. Jim in N.C.
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Wade Blocker on thu 1 mar 01
Yes, the underlying glaze melts again and can mingle with the glaze on top.
Mia in ABQ
Lizacat29@AOL.COM on thu 1 mar 01
If you glaze over a pot that doesn't come out well and refire, does the old
glaze underneath melt again, or has it already had whatever chemical reaction
and just stays the same?
Beth Christensen
David Hendley on fri 2 mar 01
In my experience, once you've fired a copper red glaze and
it didn't come out red, you can fire it from now 'till Christmas
and it will never turn red.
Now, I have never tried "striking" a failed copped red glaze,
and I guess that could conceivably work.
Striking means to reduce while the kiln is cooling, from about
1800 to 1500 degrees F.
As for the warping, you can reasonably expect a porcelain plate
to un-warp on re-firing, but you never know.....
--
David Hendley
Maydelle, Texas
hendley@tyler.net
http://www.farmpots.com/
----- Original Message -----
From: artimater
To:
Sent: Friday, March 02, 2001 7:15 AM
Subject: Re: refiring pots
I have a nice porcelain plate with an emotional attachment(not a handle)
that came out of the wood fire warped because of inadequate wadding......If
I refired in reduction could I reasonably expect it to unwarp?....Might even
the pete's copper come out red?......Would the ash glaze stay similar to
what it is?
I don't have much experience with refiring
artimator
artimator@earthlink.net
http://www.geocities.com/artimator/index.html
Dennis Mummert on fri 2 mar 01
Most of the time it just remelts. Some of the high metals glazes do weird
things around their eutectic points, but it's just glass.
-----Original Message-----
From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.CERAMICS.ORG]On
Behalf Of Lizacat29@AOL.COM
Sent: Thursday, March 01, 2001 5:58 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: refiring pots
If you glaze over a pot that doesn't come out well and refire, does the old
glaze underneath melt again, or has it already had whatever chemical
reaction
and just stays the same?
Beth Christensen
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__
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Dave Finkelnburg on fri 2 mar 01
Beth,
Just to add to what has been written, if you are firing to mid or high
range, you can produce bloating in your refired pot. The accumulated heat
work of refiring is hard on certain clay bodies, though some clay bodies
seem to stand it quite well.
If you look in the archives, there are a host of techniques for glazing
over fired, glazed pots. I have found that using a microwave to preheat a
pot to be reglazed helps the new coat of glaze set up.
Some clay artists use multiple reglazing/refirings as a decorative
technique with beautiful results, mainly because of the interaction of the
new glaze coat with the previously applied glaze.
Good luck with your work!
Dave Finkelnburg in snowy Idaho
Marcia Selsor on fri 2 mar 01
Beth,
Yes, the fired glaze will melt again. The tough part is getting the new
glaze to adhere to the fired glaze. You don't need the normal thickness
for the new glaze though because it will mix with the fired glaze during
the firing. There have been many suggstions of additives to mix with the
new glaze to get it to stick. Corn syrup is one.
Marcia
Lizacat29@AOL.COM wrote:
>
> If you glaze over a pot that doesn't come out well and refire, does the old
> glaze underneath melt again, or has it already had whatever chemical reaction
> and just stays the same?
> Beth Christensen
>
> ______________________________________________________________________________
> 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.
--
Marcia Selsor
selsor@imt.net
http://www.imt.net/~mjbmls
http://www.imt.net/~mjbmls/Tuscany2001.html
http://www.imt.net/~mjbmls/Gallery.html
artimater on fri 2 mar 01
I have a nice porcelain plate with an emotional attachment(not a =
handle) that came out of the wood fire warped because of inadequate =
wadding......If I refired in reduction could I reasonably expect it to =
unwarp?....Might even the pete's copper come out red?......Would the ash =
glaze stay similar to what it is?
I don't have much experience with refiring
artimator
artimator@earthlink.net=20
http://www.geocities.com/artimator/index.html=20
http://home.earthlink.net/~artimator/index.html
http://clubs.yahoo.com/clubs/texasceramics
"I only indulge when I've seen a snake, so I keep a supply of =
indulgences and snakes handy"
Cindy Strnad on fri 2 mar 01
Artimator,
It happens. Sometimes things will unwarp--rare, but maybe worth the try.
What have you got to lose, anyhow? Go for it.
Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
earthenv@gwtc.net
http://www.earthenvesselssd.com
Lili Krakowski on fri 2 mar 01
If you fire to same c.# it will melt again. The result may NOT be
identical to first firing. Also it may mature a bit earlier.
On Thu, 1 Mar 2001 Lizacat29@AOL.COM wrote:
> If you glaze over a pot that doesn't come out well and refire, does the old
> glaze underneath melt again, or has it already had whatever chemical reaction
> and just stays the same?
> Beth Christensen
>
> ______________________________________________________________________________
> 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.
>
Lili Krakowski
Paul Lewing on fri 2 mar 01
Beth,
As many people have said, the glaze will indeed remelt. And as Lili
said, it may change. This is because the first time around, you
essentially fritted the glaze. So the oxides are now more intimately
mixed together. A lot of heat-work has already been done on them, so
they don't need as much to melt again. So it's possible you may get some
running, especially if the glaze you apply on top is different from the
one already on there.
Paul Lewing, Seattle,
who found two pots, both delicate, small-footed vases by good friends,
on their sides, but still on the widow sill, after the earthquake.
Pretty lucky!
iandol on sat 3 mar 01
Dear Dennis Mummert,
You made the following comment in a recent posting: metals glazes do weird things around their eutectic points, but it's =
just glass.>
Which metals are you talking about?.
In addition, I understood that a substance which has frozen as a glass =
structure would not exhibit a eutectic composition. To achieve that a =
glaze has to be cooled slow enough for all of the materials to =
crystallise.
Rather, glazes remelt at their Glass transition temperature (see =
Barsoum). For sodium and potassium rich glazes this can be as low as 500 =
Celsius.
Best regards,
Ivor Lewis
Terrance Lazaroff on sat 3 mar 01
-----Original Message-----
From: David Hendley
To: CLAYART@LSV.CERAMICS.ORG
Date: Saturday, March 03, 2001 5:43 AM
Subject: Re: refiring pots
I beg to differ. It depends on the reason the red did not arrive. Our kiln
has cool spots in it and as such some reds do not mature. They come out
pink with snow crystaline areas. I have a transparent carbon trap glaze
that holds onto a glazed surface like glue. I just redip in this glaze and
refire. I still have to be careful with the amount of reduction as this
glaze will even encourage carbon trapping on a third firing. If the glaze
is white due to loosing the copper to the fire then there is little that can
be done.
One great advantage of being able to third fire with copper base is to fire
odixation then reglaze with my carbon trap and fire reduction. I get a
great mottled purple,blue red. I have just started this experience the last
kiln load and I will expand the trials the next firing.
Terrance
>In my experience, once you've fired a copper red glaze and
>it didn't come out red, you can fire it from now 'till Christmas
>and it will never turn red.
>Now, I have never tried "striking" a failed copped red glaze,
>and I guess that could conceivably work.
>Striking means to reduce while the kiln is cooling, from about
>1800 to 1500 degrees F.
>
>As for the warping, you can reasonably expect a porcelain plate
>to un-warp on re-firing, but you never know.....
>--
>David Hendley
>Maydelle, Texas
>hendley@tyler.net
>http://www.farmpots.com/
>
>
>
>----- Original Message -----
>From: artimater
>To:
>Sent: Friday, March 02, 2001 7:15 AM
>Subject: Re: refiring pots
>
>
> I have a nice porcelain plate with an emotional attachment(not a
handle)
>that came out of the wood fire warped because of inadequate wadding......If
>I refired in reduction could I reasonably expect it to unwarp?....Might
even
>the pete's copper come out red?......Would the ash glaze stay similar to
>what it is?
> I don't have much experience with refiring
>artimator
>artimator@earthlink.net
>http://www.geocities.com/artimator/index.html
>
>___________________________________________________________________________
___
>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.
Rhonda Oldland on mon 5 mar 01
I have refired tiles that have warped thinking that would fix the problem.
They cracked...Rhonda
At 07:15 3/2/01 -0600, you wrote:
> I have a nice porcelain plate with an emotional attachment(not a
handle) that came out of the wood fire warped because of inadequate
wadding......If I refired in reduction could I reasonably expect it to
unwarp?....Might even the pete's copper come out red?......Would the ash
glaze stay similar to what it is?
> I don't have much experience with refiring
>artimator
>artimator@earthlink.net
>http://www.geocities.com/artimator/index.html
>http://home.earthlink.net/~artimator/index.html
>http://clubs.yahoo.com/clubs/texasceramics
>"I only indulge when I've seen a snake, so I keep a supply of indulgences
and snakes handy"
>
>___________________________________________________________________________
___
>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.
>
>
McCroskey,Nancy on mon 5 mar 01
I refired large terra cotta tiles with cracking problems. When I
slowed the cooling cycle I was able to refire with little problem.
Nancy
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