A large 24" tall sculpture has some crazing. Is there anything I can do to save it? Sorry if this is wrong forum

[Dot]

I make rather large vertical sculptures, low-fire bisque 04, underglazes, and glaze, 04, and one of them has some crazing just in bright light, but I can't sell it with a good conscience.  Is there anything at all I can do to fix it?  It took many hours to make it.  It went through the glaze fire fine, also 04.  Any advice will be appreciated.  

[Hulk]

Hi Dot,

Welcome to the Forum!
Crazed wares, almost certainly weaker*, and liquids can be a concern, particularly where the fired clay's absorption rate is "high"...
For sculpture (and other non-food ware), however, crazing may be ok?

Reversing crazing, that may not be possible.
My understanding is that crazing occurs when the clay and glaze COE** are different enough, and that can only be corrected by changing the glaze and/or clay.
If the clay matures at a higher cone (than 04, in your case), the fit may change when fired higher, but not necessarily a better fit!

Check back for more responses...
 

*A well fitted glaze makes for stronger ware
**Coefficient Of Expansion
Co-efficient of Thermal Expansion (digitalfire.com)
see also Mr. Hansen's articles on glaze crazing, glaze fit, glaze compression 

[Dot]

Hi, Tom.  Thanks so much for the info.  The reason I was considering re-firing is I think my glaze, just a commercial clear, was a bit too thick, and maybe?? that had something to do with the crazing.  So, since it's a fit problem, perhaps firing at a higher temperature might work?   That's an uneducated guess, but I'm willing to risk it all rather than just toss it -- or give it to a relative, and they're not at all discriminating and will take anything that I've made that has a flaw in it.  I've done these pieces for years and have only had one other problem with them:  During Covid,  for some reason I had a terrible shivering problem; and, of course, there's absolutely no solution for that.  I lost around 4-5 pieces and never did find out what my problem was.  I got rid of all my clay and glaze and just started over in that situation.

Again, thanks for your help.

Dottie

[Hulk]

A glaze that is close to crazing, or crazes only a little - the crazing will be worse by putting the glaze on thickly.
That's my understanding and experience but putting on a thin layer mostly masks the problem, where the crazing will come along later, starting in the thicker parts and spreading as time marches on.

When I was re-formulating to eliminate crazing, several times I thought we had done it, but crazing began to appear ...the next day, after a few days, after a week!
With a good fit, the thick parts don't craze, the glaze withstands temperature extremes and months - years - of daily use.

Firing higher, I don't know, good question.
Would the glaze and/or clay COE change from having more heat work?
Perhaps some others have experience/knowledge and will weigh in.

Crazing can look nice! When it's not a functional flaw, isn't it "crackle" glaze?

Edited May 6 by Hulk
+1 of

[Dot]

I have a very long-time, very picky gallery owner, so that's why I'm anxious about sending it as is.  His gallery is my "bread-and-butter," so I don't want to upset things.  Yes, the crazing doesn't bother me, but . . . .   Plus, it's only about 8 hours to get another one built, fired, etc.  

Thanks again.  I agree with what you said about the crazing's coming back slowly even with a fix, (bad fit is bad fit) and I really don't think the higher fire will solve the problem. (I think I'm going to have another happy relative pretty soon.) 

I know from experience, too, that spending too much time on a piece that has a problem is usually a waste of time and that I could have made another one in the time I've fussed over the bad piece -- which probably wouldn't have turned out right anyway.  Oh, well, it's only work -- and experience.  

Thanks.

[Min]

2 hours ago, Hulk said:

Firing higher, I don't know, good question.
Would the glaze and/or clay COE change from having more heat work?

Underfired glazes can craze for sure.

I always stress test glazes for fit before putting them into production. 

[Dot]

Yes, I should have.  I had been away from clay for over a year and just dived back in without testing anything.  Bad choice.  From what you say about underfired can craze, I guess it won't hurt to give it a try.  Thanks so much.

[Callie Beller Diesel]

While I’m one of the first people who will usually say it’s a bad idea to sell crazed functional ware, why are concerned about crazing on sculptural work? Sculptures don’t have the same durability demands placed on them as dishes. They might have their own durability demands if they’re outside, but I digress.

[Dot]

I know my customer, and he's a picky gallery owner.  And, I have an exclusive contract with him, so selling it retail is not an option.  My decision is to give the higher-fire a try; and if it doesn't work, give it to one of my relatives, who won't care if it isn't perfect.   Thanks to all of you who responded; you helped me make my decision.

[Rae Reich]

Rub ink into the crackles and say, “I meant to do that”?

[Dot]

Thanks!  If the second firing doesn't work, I'll try that.

[Hulk]

Please do post an update on the re-fire...

[Dot]

will do

[Piedmont Pottery]

17 hours ago, Rae Reich said:

Rub ink into the crackles and say, “I meant to do that”?

I agree strongly.  India ink enhanced crazing can be very dramatic and beautiful.  If you or the gallery owner can't live with the result, the ink will burn off if you refire the piece.

[PeterH]

5 hours ago, Piedmont Pottery said:

I agree strongly.  India ink enhanced crazing can be very dramatic and beautiful.  If you or the gallery owner can't live with the result, the ink will burn off if you refire the piece.

If the crackle was pretty dense and it does re-craze it might be worth considering an "iron wire and golden thread" effect.

 

[Dot]

Thanks so much; I'll consider that.  I've heard of gold in cracks but never thought of it in crazing.  I'll look into it.  I have some very low-fire gold "over-fire" (probably not the correct word, but that's the best I can do at this moment) that might be interesting.  Might as well play with it.  I'll refire it once at a slightly higher temp; and if that doesn't work at all, I'll give some of the other options, especially the gold, a try.  Thanks.