Ben xyz Posted October 18, 2022 Report Share Posted October 18, 2022 Apologies before for this newbie question. Have read that it is the trapped water that actually causes an explosion of a clay piece when firing vs trapped air. Now considering firing an enclosed (hollow) form (5”x7”x4”). Will this be alright or is it important to have a hole somewhere in the form to avoid an explosion. It is a public kiln. Thanks! Quote Link to comment Share on other sites More sharing options...
Kelly in AK Posted October 18, 2022 Report Share Posted October 18, 2022 I know a lady who puts hollow pillow like feet on her pots. She said if she doesn’t put a pinhole in them they crack off at the attachment point. It’s certainly water to steam that causes explosions, but there are other consequences to sealing off a volume of air in clay. A pinhole in a place that doesn’t get sealed by glaze eliminates those. Bill Kielb and Rae Reich 2 Quote Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted October 20, 2022 Report Share Posted October 20, 2022 I used to make all kinds of hollow knobs on lids. I would put a pinhole in the bottom of them, and it was never a problem to seal it over with glaze, but maybe it’s an issue with larger forms? I think it’s one of those things that if you want to be able to do it, test to find where the limits are with your materials and your own practice. Rae Reich 1 Quote Link to comment Share on other sites More sharing options...
Kelly in AK Posted October 20, 2022 Report Share Posted October 20, 2022 Thank you @Callie Beller Diesel, perfectly said! That “sealed over by glaze” bit was totally an assumption on my part. I tend to figure if it can go wrong it will and wind up extrapolating in a careful direction. Personal, first hand experience in ceramics is what you can count on most. If you did it and it works, you know it works. I’m reminded of Josh DeWeese, who told me “You don’t have to score, just use slip and really stick that handle on.” I have some of his pots, use them regularly, the handles don’t pop off. Do I still score attachments? Yeah. Can’t help it. Rae Reich and Callie Beller Diesel 2 Quote Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted October 21, 2022 Report Share Posted October 21, 2022 My working theory on why you get so many different instructions about slip/score/water/no water is that it varies by clay body. When I switched from a white high fire stoneware to a mid fire red, the handle attaching method I’d been using resulted in more cracked handles than I’d ever had in my life! The white one wanted slip and score, but if I do that with my red stoneware, they take forever to grab and the slip shrinks too much and I get those nuisance edge cracks. The red one wants score plus a dab of water only. Min, Kelly in AK and LeeU 3 Quote Link to comment Share on other sites More sharing options...
Min Posted October 21, 2022 Report Share Posted October 21, 2022 2 hours ago, Callie Beller Diesel said: My working theory on why you get so many different instructions about slip/score/water/no water is that it varies by clay body. +1 for this! I think it goes far beyond attaching handles and that is perhaps why it takes so long to get processes nailed down when starting out. Ask 5 different potters how they throw / slab build / dry / make attachments / which batts work best / bisque fire/ glaze fit / glaze firing and so forth and you could very likely get at least 5 different answers for each process. Type of clay, working environment (humidity etc), work style, clay thickness, material chemistry etc all come into play. Definitely not a one size fits all scenario for much of what we do. Callie Beller Diesel and oldlady 2 Quote Link to comment Share on other sites More sharing options...
Ben xyz Posted October 21, 2022 Author Report Share Posted October 21, 2022 Thanks for all the responses - appreciate it. Spoke with the studio manager who said it would not be an issue with the clay they’re selling and the temps they’re firing at. Since it’s a community studio, I didn’t want to wipe out other peoples’ work if mine decided to self-destruct. Will report back in if any of my sealed forms decide to misbehave. Quote Link to comment Share on other sites More sharing options...
neilestrick Posted October 23, 2022 Report Share Posted October 23, 2022 20 hours ago, Rockhopper said: A sealed (or nearly sealed) form will take longer to dry than an open one This. It takes forever for sealed forms to dry completely. The outside can be bone dry but the inside will still be leather hard. It also takes longer for the heat of the kiln to penetrate and drive off the last bit of moisture, so do a good long preheat and ramp slowly at first. Ben xyz 1 Quote Link to comment Share on other sites More sharing options...
Pres Posted October 23, 2022 Report Share Posted October 23, 2022 Over the years I have made several hollow pieces in my pots for one reason or another, The honey jars I make have hollow round or beehive shaped handles hollow inside, with a hole in the underside of the lid where the honey scoop stem is attached with an open end at the attachment point to the lid, Years ago I was making whistles hollow with open areas. At the same time I made rattles, clay balls dried or bisqued, placed inside of a thrown hollow form with a handle area trimmed for gluing a wooden dowel into. Many times I would put pin holes in pieces, but often not. I think in the long run it is about the joins and the dryness. If you have wet areas inside the void, the steam and the air expansion will stress join areas. I you make certain to have no wet areas and fire slowly your joins should not stress. All of course IMHO. best, Pres Ben xyz 1 Quote Link to comment Share on other sites More sharing options...
Ben xyz Posted October 23, 2022 Author Report Share Posted October 23, 2022 The key sounds like it’s making sure the piece completely dry before firing (which takes longer than usual, due to the enclosed area). Thanks for the responses. Pres 1 Quote Link to comment Share on other sites More sharing options...
Babs Posted October 23, 2022 Report Share Posted October 23, 2022 2 hours ago, Ben xyz said: The key sounds like it’s making sure the piece completely dry before firing (which takes longer than usual, due to the enclosed area). Thanks for the responses. And a slow candling and slower ramps at start of bisque firing Pres 1 Quote Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted October 24, 2022 Report Share Posted October 24, 2022 On the plus side, when you make hollow knobs, you don’t have to worry about small extending bits drying faster than the rest of the pot. Ben xyz 1 Quote Link to comment Share on other sites More sharing options...
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