How dose one "fill in" the cracks on a crackle glaze?

Bob Masta wrote:
On Tue, 21 Nov 2006 16:07:08 +0000, Eddie Daughton
wrote:

There be a man in this area caaleed Rupert Andrews and he makes the most
incredible crackle glazed pots.... Don't know how he does it but it
seems to entail firing below matureing temp and then using another glaze
and going all the way....
Hope this helps
look him up on Google...
Hugs
Eddie

Wow! I especially liked this pot:
http://www.themousehole.com/images/andrews01.jpg

This concept of being able to refire after filling the craze lines
with oxide (if that is in fact what Rupert Andrews is doing)
seems to call for some serious experimenting.
First of all, we should note that this has nothing to do with
the shrinkage that the body goes through at maturation, as such
Crazing happens on cool-down due to a difference in
coefficients of expansion between body and glaze.
However, the question is whether maturation causes a change
in body COE. I suggested this on Clayart a couple of years ago,
based on some crazing issues I had that were cured by moving
up to a higher cone, and Ron Roy pointed out that the more
likely explanation was that the changes I had made to the glaze
to get it to not run off the pot were also changing the COE. I
never followed up on that at the time... maybe now is the time!

The other thing is that if we fire at a low temperature and get
crazing, then fill in the lines with oxides and refire to a higher
temperature, that means the original glaze had to be able to
melt at the low temp, so that it could craze on the
initial cooling. Then the *same glaze* has to stay on the pot
when fired to a higher temp that matures the body. Seems
like a delicate balancing act. Actually, if there is any merit to
the idea of the body COE changing so that the second firing
doesn't craze, then maybe the oxide-filled craze lines will
run a bit... could be a nice effect on its own.

What I have heard of is simply using a normal crazing glaze,
filling the lines with oxide, and refiring the same way. Of
course, on the second firing you will get additional craze lines,
but they won't have the oxide accent.

How about instead of filling with a pure oxide, we find some
mix that melts easily at a much lower temperature than the
original glaze? That way the colors could melt into the pot before
the original glaze softened enough to move, and hence to re-craze
on cool-down. I suspect that this may be tricky, since I think that
it will take very little temperature to soften the original glaze
enough to re-craze.

Just some thoughts...




Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator
Ball milling the oxide to ever so small helps as well....

could he be using a RAKU process which can cause that effect... guy
"Eddie Daughton" wrote in message
...
Bob Masta wrote:
On Tue, 21 Nov 2006 16:07:08 +0000, Eddie Daughton
wrote:

There be a man in this area caaleed Rupert Andrews and he makes the most
incredible crackle glazed pots.... Don't know how he does it but it
seems to entail firing below matureing temp and then using another glaze
and going all the way....
Hope this helps
look him up on Google...
Hugs
Eddie

Wow! I especially liked this pot:
http://www.themousehole.com/images/andrews01.jpg

This concept of being able to refire after filling the craze lines
with oxide (if that is in fact what Rupert Andrews is doing)
seems to call for some serious experimenting.
First of all, we should note that this has nothing to do with the
shrinkage that the body goes through at maturation, as such
Crazing happens on cool-down due to a difference in
coefficients of expansion between body and glaze.
However, the question is whether maturation causes a change
in body COE. I suggested this on Clayart a couple of years ago,
based on some crazing issues I had that were cured by moving
up to a higher cone, and Ron Roy pointed out that the more
likely explanation was that the changes I had made to the glaze
to get it to not run off the pot were also changing the COE. I
never followed up on that at the time... maybe now is the time!

The other thing is that if we fire at a low temperature and get
crazing, then fill in the lines with oxides and refire to a higher
temperature, that means the original glaze had to be able to
melt at the low temp, so that it could craze on the
initial cooling. Then the *same glaze* has to stay on the pot
when fired to a higher temp that matures the body. Seems like a delicate
balancing act. Actually, if there is any merit to the idea of the body
COE changing so that the second firing
doesn't craze, then maybe the oxide-filled craze lines will
run a bit... could be a nice effect on its own.

What I have heard of is simply using a normal crazing glaze,
filling the lines with oxide, and refiring the same way. Of
course, on the second firing you will get additional craze lines,
but they won't have the oxide accent.

How about instead of filling with a pure oxide, we find some
mix that melts easily at a much lower temperature than the
original glaze? That way the colors could melt into the pot before
the original glaze softened enough to move, and hence to re-craze
on cool-down. I suspect that this may be tricky, since I think that
it will take very little temperature to soften the original glaze
enough to re-craze.

Just some thoughts...




Bob Masta
dqatechATdaqartaDOTcom
D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator
Ball milling the oxide to ever so small helps as well....