ABlanc Posted August 24, 2022 Author Report Share Posted August 24, 2022 1 hour ago, Babs said: How are you drying this multi layered slab? What is your firing schedule? Had a teacher who said many times, to non listening teenagers, " It is not the material but the operator", i.e. the process, design etc being applied so before troting down to the store, check your steps, or it could be Murphy.... Happening all over your kiln? Happening all over the kiln: in a word yes. We are getting massive dunting cracks (or more accurately gaping fissures of doom) in work that is larger scale hand built lamps using same B mix. We have tried everything - slow drying, slow firing schedule, glazing insides, etc all to no avail so perhaps perhaps we are the common denominator and not the clay. Pic attached of example of these pieces that we salvaged through repairing the cracks in the end but it’s rare we get one without cracks completely. I figured it was the B mix clay given how widely different these two designs (the flat slab light versus these big organic coil pieces) are and each are having problems but perhaps not. Quote Link to comment Share on other sites More sharing options...
Babs Posted August 24, 2022 Report Share Posted August 24, 2022 That is so frustrating indeed. Have you fellow potters working with a different body that also hand build? Maybe get a bag or two of clay from them to try? How does it perform for thrown pots? Quote Link to comment Share on other sites More sharing options...
Kelly in AK Posted August 24, 2022 Report Share Posted August 24, 2022 (edited) I see rounded edges on the glaze along the crack. It’s not a dunt, it was there before the glaze melted. This is a complex form, if the walls are attached at a different consistency than the slab it’s going to set up big tension. I also notice a lot of sponge marks on the exposed clay surfaces. It suggests some re-wetting/overworking happened, complicated shapes in tension don’t like that. The crack was either already there (happened in the greenware stage but wasn’t evident), or it happened on the way up. At the risk of sounding like a parrot, there are bodies much better suited to this kind of work than B-mix. That said, it’s always good to re-evaluate technique when unexpected things like this happen. This article by Vince Pitelka may also be helpful: https://www.vincepitelka.com/wp-content/uploads/2021/06/Rolling-Slabs-Platelet-Grain-Structure-and-Clay-Memory.pdf Edited August 24, 2022 by Kelly in AK Babs 1 Quote Link to comment Share on other sites More sharing options...
Phil0110 Posted August 31, 2022 Report Share Posted August 31, 2022 maybe the temperature in the oven has risen Quote Link to comment Share on other sites More sharing options...
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