Anna M Posted October 18, 2022 Report Share Posted October 18, 2022 I have a number of pieces which leak. So I need to increase firing temp for this clay. The bowls and cups I tested for leaking (I put water in them overnight) can I put these items back into the kiln and refire at higher temp? Or because they have had water in them they will explode? Thanks Quote Link to comment Share on other sites More sharing options...
Babs Posted October 18, 2022 Report Share Posted October 18, 2022 What cone did you fire to? What cone does your glaze mature at? What does it say on your bag of clay re cone that clay requires for vitrification? Just that if glaze already on pot is a lowfire glaze and you need to go to a higher cone, your glaze may run off pot onto shelf. Re drying pot not necessary , justlike you can put pots just glazed straight into kiln for glaze firing. Quote Link to comment Share on other sites More sharing options...
Anna M Posted October 19, 2022 Author Report Share Posted October 19, 2022 Hi Babs, I fired to a hot cone6, (witness cone also showed cone 7 half bent) the clay had a firing range of 1180-1250 degrees, and I used a range of glazes amaco cone 5-6 glazes, and some terra colour which are 1200-1280 degrees. the clay company are sending me a replacement bag, they think it should be vitrified at the temp I fired at. however I’m just wondering all the pottery I have that leaks can I try to go higher - maybe by 10degrees to try find vitrification point. Can I put amaco cone 6 glazes to cone 7? thanks so much for your help Quote Link to comment Share on other sites More sharing options...
Babs Posted October 20, 2022 Report Share Posted October 20, 2022 I'd wait for your new bag of clay and when you get to glazing the new pots, put one of your unvitrified pots on a waster piece of clay, no need to pre bisque but could to feel safe. Put in hot spot in kiln The extra heatwork from refiring may nudge it over the line or may need to get that cone 7 over What glazes on pots which leaked ?variety or the higher maturing? Might save you an unsuccessful firing. Could put all on waster saucers and risk a melt and run of glazes. Would be a midfire clay which would be better I am sure. Quote Link to comment Share on other sites More sharing options...
Rae Reich Posted October 20, 2022 Report Share Posted October 20, 2022 Does anyone else think that a leaky, glazed low-fire piece that has been wetted will not suffer in a refire? I think there might be some glaze popping off, possibly some cracking or breakage, even if refired to the same temp. One way to tell … Quote Link to comment Share on other sites More sharing options...
Babs Posted October 20, 2022 Report Share Posted October 20, 2022 4 hours ago, Rae Reich said: Does anyone else think that a leaky, glazed low-fire piece that has been wetted will not suffer in a refire? I think there might be some glaze popping off, possibly some cracking or breakage, even if refired to the same temp. One way to tell … OP firing to cone 6 with cone 7 half way down. CKay maturing at 1250 d C so not a low fire imo. @Anna M are your pots glazed all over? Which pots did not leak? Could weigh totally dry pot, soak totallly overnight and weigh to test absorbency % Quote Link to comment Share on other sites More sharing options...
Kelly in AK Posted October 21, 2022 Report Share Posted October 21, 2022 The local clay I use has a very narrow firing range. Cooler spots in the kiln yield porous pots and unsatisfactory glazes. I don’t hesitate to refire those. Sometimes I apply additional glaze. I also fire cone 6 soda using commercial clays and those don’t always come out as nice as I’d like. They get refired too. I don’t put the refires anywhere near the direct flame path. Haven’t had problems with cracking or shivering on those and saved quite a few pots I was considering throwing out. I was taught that refiring glazed ware rarely made anything better and was risky, so I resisted it for many years. Quote Link to comment Share on other sites More sharing options...
Rae Reich Posted October 21, 2022 Report Share Posted October 21, 2022 For clarification, my concern is about the fact that a vessel with known porosity - leaking - has been thoroughly soaked. Water has infiltrated. Another firing might cause the residual water to leave the pot expeditiously, possibly causing damage. Quote Link to comment Share on other sites More sharing options...
Babs Posted October 21, 2022 Report Share Posted October 21, 2022 Yeh, I haven't witnessed that. Water would be out of it before glaze melt and sealed off escape routes? Test and see I guess Quote Link to comment Share on other sites More sharing options...
Kelly in AK Posted October 21, 2022 Report Share Posted October 21, 2022 Ah, yes, I see. Putting a waterlogged glazed pot back into the kiln right away could be cause for concern. Unusual situation. I haven’t tried that, so I don’t know. One big surprise I did have was a piece of bisque exploding. It was freshly glazed and right into the kiln. A very tight grained porcelain. The ramp up to 1000° was pretty fast, wood kiln, unequal heat paths. This one pot and no others blew to bits. I know it was bisque because I glazed it. Never seen it before or since. On the other hand I’ve seen loads of freshly glazed work go right into a kiln that started the minute it was loaded, without incident. A totally soaked, already glazed, almost vitreous (?) pot right into the kiln...yep, try it. Or just dry the pot a few days. My concerns have only been thermal shock cracks, dunting, and overfiring (as mentioned-each firing adds a little heat work to the pot). Rae Reich 1 Quote Link to comment Share on other sites More sharing options...
Chilly Posted October 30, 2022 Report Share Posted October 30, 2022 On 10/20/2022 at 4:50 PM, Rae Reich said: Does anyone else think that a leaky, glazed low-fire piece that has been wetted will not suffer in a refire? I think there might be some glaze popping off, possibly some cracking or breakage, even if refired to the same temp. One way to tell … I've re-fired some almost identical pots and had one succeed and one fail. My thought is, "if it's no use as it is, what is there to lose by re-firing". But always use waster cookies and think about what else is on the same shelf. Rae Reich 1 Quote Link to comment Share on other sites More sharing options...
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