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Stoneware Touching

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okay. I was wondering can unglazed stoneware touch in a glaze firing? lets say for example you had a bunch of vases that were unglazed on the outside, can they touch one another for maximum space usage in the kiln? also if you had a 50/50 blend of a porcelain and stoneware could they touch or would the amount of porcelain in the blend weld the peices together? Thank you all :D

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simon leach often stacks his GP bowls rim to rim when he glaze fires.   He will often just glaze the inside and leave the rims unglazed.

 

 

 

at about 14 min he shows a small lidded cup? (dont know what you call it) glazed on the outside,  were the lid sits on the body is unglazed as well as the underside of the lid.   He often uses the handle of a hammer to give items like this a slight tap to "release" them.    (you'll often see him do it to his rim-rim GP bowls also) see 15.20 ish

Karen B likes this

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If you think about it, the unglazed stoneware is touching significantly when you fire a lid in place to minimize warping of the vessel.  Many times the lid will need a rap to get it loose, so something is going on, but not so much it welds the lid.

 

John

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That is a great video thank you for posting it. I fire boxes quite frequently and have been struggling a bit getting them apart after firing even when there isn't any glaze to be seen once I get them apart. Watching how he raps the pieces with a WOODEN handle I went AhA! Today when I opened my kiln containing 30 boxes I grabbed a hearty dowel and just tapped around the top and pop they came off. I lost NO boxes due to sticky lids. I am continuously reminded of how great this forum and the people on it are. Thank you once again.

 

Terry

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It depends on the clay and what temperature it is fired to. I use a dark red ^6 stoneware. The high iron content may make it a little fluxier when it reaches maturity, increasing the chances of sticking. I do fire jar lids on the jar and they need to be rapped to loosen, as said above. Occasionally there will be a small chip out of one, especially if I have fired all the way to ^6, or close to that. I usually fire to a solid ^5, large witness cone touching the shelf, or close to that. That minimizes the problem. And for these reasons I probably wouldn't fire unglazed rims touching, and I always use kiln wash even if the glazes don't run, as pots can stick to bare shelves.

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Terry, I learned the "wooden handle" trick in college, when one of my lids stuck. I was a little concerned, when my instructor went to do it, but I trusted him. I don't think my students trust me quite as much, but they are teenagers, they don't trust anybody,

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I tell my students if they ever have glaze run to my shelves i will take a 2x4 to their pot...it sounds like a threat but i go on to explain that their pot is more likely to survive being tapped of by a wooden 2x4 than a hammer. So tapping lids with wood is also safer than prying lids off.

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I am a scaredy cat. I put the casserole in a sink full of warm water and sit an icepack on the lid. It takes ten minutes or so, because ceramic materials do not transmit heat well, but eventually, the difference in expansion breaks the  'stick'.

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