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

i've heard of this too, but never wanted to do any myself. i think tea is used sometimes. as with an old tea cup. the cracks start to show up in time.

see ya

steve

Mike.

snipped-for-privacy@yahoo.com wrote:

I've also heard India ink recommended. When I wanted to try this technique, I didn't have any India ink so I used what I had, which was ink for a stamp pad. Seemed to work OK. Also tried black artist's acrylic paint, suitably thinned with water, and it worked also. Indelible flet-tip ("Sharpie", etc) works as well.

I was trying this on Egyptian paste beads, so you may get different results on stoneware, etc. But I suspect that just about anything that is dark and relatively permanent will work.

Best regards,

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

Home of DaqGen, the FREEWARE signal generator

There's a technique I've read about, but never tried, that is a more permanent way of retaining the crackle lines but still ending up with a watertight glaze surface. It involves firing the object to a temperature lower than the final maturation point of the clay body, at which point there is a mismatch in the coefficient of expansion of the clay versus the glaze, causing a crackle pattern. Oxide is rubbed into the cracks, then the piece is refired to a higher temperature. At that point, the COEs match, so the glaze reflows but doesn't crack - but the oxide is still there, as color only. Needless to say, there's probably a lot of experimentation required to get this to actually work...

Andrew Werby

----- Original Message ----- From: Newsgroups: rec.crafts.pottery Sent: Saturday, November 18, 2006 5:29 PM Subject: How dose one "fill in" the cracks on a crackle glaze?

I'd love to find an all-ceramic method like you mention, but I don't understand the theroy behind this. The cracks appear on cooling, so what prevents new cracks from forming after the final firing? I think you'd get the effect you wanted on the cracks you filled with oxide, but then there would always be other unfilled cracks as well, from the final cool-down.

Or am I missing something?

Best regards,

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

Home of DaqGen, the FREEWARE signal generator

So if the pot has been fired and done all the shrinking it is going to do, and the glass (glaze) remelts and spreads out.... it seems to me that now there is not an issue of fit because there is no shrinkage of the body.... but then I'm not clear on what is going on in crazing. For instance, why does the crazing happen after the pot has already cooled down?

[Look guys, I never said I'd made this work; I'm just reporting about an approach I'd heard about. The idea is that a glaze that doesn't fit (and cracks) when underfired, due to mismatched coefficients of expansion, does fit (and doesn't crack) when it reaches maturity. I've never seen it happen, and it could be a potters' legend, for all I know. Is there anything about it on Clayart?]

Andrew

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

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

Wow! I especially liked this pot:

concept of being able to refire after filling the craze lineswith 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 suchCrazing happens on cool-down due to a difference incoefficients of expansion between body and glaze.However, the question is whether maturation causes a changein body COE. I suggested this on Clayart a couple of years ago,based on some crazing issues I had that were cured by movingup to a higher cone, and Ron Roy pointed out that the morelikely explanation was that the changes I had made to the glazeto get it to not run off the pot were also changing the COE. Inever 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

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 news:456613f7 snipped-for-privacy@mk-nntp-2.news.uk.tiscali.com...