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repairing stress cracks in fired pieces

updated wed 4 dec 02

 

Snail Scott on sat 30 nov 02


At 10:08 PM 11/30/02 -0500, you wrote:
>I have a few pieces (white stoneware) that came out of a wood firing
>with some stress cracks. Wondering if there is any way to repair
>these, either with some sort of filler that sets up without heat, or
>by filling with something and refiring in electric kiln? (Cone 6)


For non-functional (decorative/art) pieces ONLY,
paste epoxy and putty epoxy fillers will work.
If you will need to paint the patch to hide it,
I recommend Bondo, or any other auto-body repair
filler. Unlike most other epoxies (yes, they're
a type of epoxy) they accept paint well. They're
designed to, after all! Normal epoxies need to
be sanded to give 'tooth' before painting, and
even then, it's not as good a bond as I'd prefer.
(It's a bit trickier to mix Bondo in small
quantities, since it's not a 50/50 mix, but it's
pretty forgiving of variations in proportion.)

However, Bondo is a filler, NOT an adhesive. If
your cracks are such that they may compromise the
structural strength of the piece, fill them with
a standard paste epoxy forced into the cracks.
Keep the level below the surface of the work,
though, so you can fill it the rest of the way
with Bondo.

-Snail

Elizabeth Fisher on sat 30 nov 02


I have a few pieces (white stoneware) that came out of a wood firing
with some stress cracks. Wondering if there is any way to repair
these, either with some sort of filler that sets up without heat, or
by filling with something and refiring in electric kiln? (Cone 6)


I noticed the mention of a clay expoxy below, and wondered if this could work?



thanks in advance, Liz Fisher



>. . . Also I bought the
>clay epoxy that Stephanie recommended and have found MANY uses for it
>already, including beefing up some of the skinny toes that I had made
>previously. Elizabeth
>

Elizabeth Fisher on mon 2 dec 02


Snail:


Appreciate that advice. Next question - In non-functional work, do
folks just leave (non-structural) cracks in as part of process? With
explanation to end owner/buyer or no? Not sure if better just to
leave cracks as evidence of (admittedly not perfect) process, or try
to fill and match finish?



Liz Fisher








>At 10:08 PM 11/30/02 -0500, you wrote:
>>I have a few pieces (white stoneware) that came out of a wood firing
>>with some stress cracks. Wondering if there is any way to repair
>>these, either with some sort of filler that sets up without heat, or
>>by filling with something and refiring in electric kiln? (Cone 6)
>
>
>For non-functional (decorative/art) pieces ONLY,
>paste epoxy and putty epoxy fillers will work.
>If you will need to paint the patch to hide it,
>I recommend Bondo, or any other auto-body repair
>filler. Unlike most other epoxies (yes, they're
>a type of epoxy) they accept paint well. They're
>designed to, after all! Normal epoxies need to
>be sanded to give 'tooth' before painting, and
>even then, it's not as good a bond as I'd prefer.
>(It's a bit trickier to mix Bondo in small
>quantities, since it's not a 50/50 mix, but it's
>pretty forgiving of variations in proportion.)
>
>However, Bondo is a filler, NOT an adhesive. If
>your cracks are such that they may compromise the
>structural strength of the piece, fill them with
>a standard paste epoxy forced into the cracks.
>Keep the level below the surface of the work,
>though, so you can fill it the rest of the way
>with Bondo.
>
> -Snail
>
>______________________________________________________________________________
>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.

Snail Scott on mon 2 dec 02


At 10:06 AM 12/2/02 -0500, you wrote:
>Snail:
>...In non-functional work, do
>folks just leave (non-structural) cracks in as part of process? With
>explanation to end owner/buyer or no?


If it looks OK, and 'process' is consistent with the style
of the work, then maybe you can leave it. If it just
looks broken, then no. 'Rough and loose' is a legimate
look, but only if it's the one that suits that piece. (A
Voulkos aesthetic? Or a Duckworth aesthetic?) And don't
'explain' to the buyer. If it's a good piece of work as it
stands, then it's a good piece of work. If you think it
needs an explanation or an excuse, then it's probably not
something you should be presenting to the buyer anyway.
If you're afraid the buyer will think it looks defective,
then maybe you're right. So fix it if you need to and
can. If you need to and can't, then don't offer it for
sale. (Maybe as a 'second' in a studio sale, but never in
a gallery or show.)

The 'functionality' of sculpture is judged by different
standards than for pottery. Its function lies primarily in
its appearance. But, it must, (IMHO) still be 'as sturdy
as it looks'. Someone buying a work of art made of paper
and string will assume its fragility and treat it
accordingly. A work of clay is assumed to be breakable if
dropped, but should sustain reasonable handling, and be
reasonably archival in its execution. If it looks like an
outdoor piece, it should be weatherproof, etc. And even
if its structural properties are unaffected, the 'function'
of appearance is still a consideration. Does it REALLY
look good? Or does it look patched?

I know that the 'fix it' philosophy sits badly with the
functional potters out there, and they're right - for
their work. For a sculptor, losing a single piece can be
like losing a kilnload for a potter. A piece that takes
an hour to make...make a new one! If it takes a month to
make...fix it. It's not hard to do the math...will it take
longer to repair or to replace? And will it be AS GOOD FOR
ITS INTENDED USE as it would have been otherwise? IF the
net result will be substandard, just let it go to the
boneyard. If not, there is no moral or ethical deficiency
in repair. But be strict in your standards - is it REALLY
as good as it should be? Questionable craftsmanship is
not acceptable in sculpture any more than it is in pottery.

Potters have it tough...finding that perfect personal
intersection of form and function, executed to meet the
high demands of daily use in a mass-production culture.
No room for error there. A scupltor's standards are
different and yes, lower, in some senses. No need for
testing glaze safety, no requirement to avoid sharp edges
or thick walls. Stackability? Phooey! But sculpture does
have standards, and work that needs an apology is work
that shouldn't leave the studio.

I often make work in segments which are fired separately
and attached after firing. Under these conditions, it
seems silly to distinguish between an epoxy attachment
made by design, and one necessitated by circumstances.
But ONLY if the net outcome is still a first-class piece.
If the work doesn't stand on its own as a fine example of
your work, don't show it. No excuses.

-Snail

Elizabeth Fisher on mon 2 dec 02


Whoa! I am with you. Points taken. I'm figuring to use the pieces
that cracked as a learning experience. I'll just put them in front of
me as a reminder to be more careful (think I may not have compressed
clay enough in some stress prone areas and may not have let moisture
content stabilize)! Appreciate your advice, as always.




>At 10:06 AM 12/2/02 -0500, you wrote:
>>Snail:
>>...In non-functional work, do
>>folks just leave (non-structural) cracks in as part of process? With
>>explanation to end owner/buyer or no?
>
>
>If it looks OK, and 'process' is consistent with the style
>of the work, then maybe you can leave it. If it just
>looks broken, then no. 'Rough and loose' is a legimate
>look, but only if it's the one that suits that piece. (A
>Voulkos aesthetic? Or a Duckworth aesthetic?) And don't
>'explain' to the buyer. If it's a good piece of work as it
>stands, then it's a good piece of work. If you think it
>needs an explanation or an excuse, then it's probably not
>something you should be presenting to the buyer anyway.
>If you're afraid the buyer will think it looks defective,
>then maybe you're right. So fix it if you need to and
>can. If you need to and can't, then don't offer it for
>sale. (Maybe as a 'second' in a studio sale, but never in
>a gallery or show.)
>
>The 'functionality' of sculpture is judged by different
>standards than for pottery. Its function lies primarily in
>its appearance. But, it must, (IMHO) still be 'as sturdy
>as it looks'. Someone buying a work of art made of paper
>and string will assume its fragility and treat it
>accordingly. A work of clay is assumed to be breakable if
>dropped, but should sustain reasonable handling, and be
>reasonably archival in its execution. If it looks like an
>outdoor piece, it should be weatherproof, etc. And even
>if its structural properties are unaffected, the 'function'
>of appearance is still a consideration. Does it REALLY
>look good? Or does it look patched?
>
>I know that the 'fix it' philosophy sits badly with the
>functional potters out there, and they're right - for
>their work. For a sculptor, losing a single piece can be
>like losing a kilnload for a potter. A piece that takes
>an hour to make...make a new one! If it takes a month to
>make...fix it. It's not hard to do the math...will it take
>longer to repair or to replace? And will it be AS GOOD FOR
>ITS INTENDED USE as it would have been otherwise? IF the
>net result will be substandard, just let it go to the
>boneyard. If not, there is no moral or ethical deficiency
>in repair. But be strict in your standards - is it REALLY
>as good as it should be? Questionable craftsmanship is
>not acceptable in sculpture any more than it is in pottery.
>
>Potters have it tough...finding that perfect personal
>intersection of form and function, executed to meet the
>high demands of daily use in a mass-production culture.
>No room for error there. A scupltor's standards are
>different and yes, lower, in some senses. No need for
>testing glaze safety, no requirement to avoid sharp edges
>or thick walls. Stackability? Phooey! But sculpture does
>have standards, and work that needs an apology is work
>that shouldn't leave the studio.
>
>I often make work in segments which are fired separately
>and attached after firing. Under these conditions, it
>seems silly to distinguish between an epoxy attachment
>made by design, and one necessitated by circumstances.
>But ONLY if the net outcome is still a first-class piece.
>If the work doesn't stand on its own as a fine example of
>your work, don't show it. No excuses.
>
> -Snail
>
>______________________________________________________________________________
>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.

Snail Scott on tue 3 dec 02


At 09:23 PM 12/2/02 -0500, you wrote:
>>If the work doesn't stand on its own as a fine example of
>>your work, don't show it. No excuses.

>Whoa! I am with you. Points taken...


Sorry; shouldn't have used your personal circumstance
as an opportunity to wear my soapbox out! It was a
topic that had some up recently with a student,
though, and I was on a roll...nothing personal!

-Snail