Chilly Posted November 11, 2015 Report Share Posted November 11, 2015 Hummmmm. I've often re-fired ^6 stuff and the crawling has reduced, not got worse. You said the glazes looked "unfired" or "un-matured" from big kiln. My best suggestion is to re-fire, for less time/soak and slightly lower temperature than the first half. I've also glazed stuff that got (inadvertantly) bisqued to ^6. Have you tried removing the glaze? I'm guessing it may have started to harden and will not remove anyway. What have you got to lose from trying it again, apart from £5.00 of electricity? Link to comment Share on other sites More sharing options...
Babs Posted November 11, 2015 Report Share Posted November 11, 2015 Think the glaze would have sintered by the first firing. Try gently up , don't know your firing schedule,nothing to lose......hmmm Don't think you'll be able to remove the glaze Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted November 12, 2015 Report Share Posted November 12, 2015 sorry for your pots Can't seem to come up with many reasons why a 12 hour 880 firing would crawl a glaze. Not sure what is the actual mechanism that makes a glaze crawl. Too high surface tension? If you are sure that no mistakes made in mixing glaze and making pots then I am stumped. Link to comment Share on other sites More sharing options...
Celia UK Posted November 15, 2015 Author Report Share Posted November 15, 2015 After showing a glaze expert my test tiles, cone packs and both the twice-fired and once-fired pieces, the view is that the long firing at 880oC will have caused significant chemical changes to the clay and also possibly the clay content of the glaze. This in combination with a thicker than necessary glaze layer probably caused the dramatic crawling of the glaze. Made the decision to get out the hammer and bin the 2nd half of the load, rather than risk a similar very messy firing. Probably need to replace the elements in the kiln that failed to get past 900oC - having the definitive check on Wednesday. Many thanks for all your comments and suggestions. Link to comment Share on other sites More sharing options...
oldlady Posted November 16, 2015 Report Share Posted November 16, 2015 celia, just FYI, if you are going to fire pieces shaped like the ones you pictured, move the smaller ones closer to the edge so the large one can be closer to the center and not touching the wall. Link to comment Share on other sites More sharing options...
Mark C. Posted November 16, 2015 Report Share Posted November 16, 2015 I see a peep hole in your kiln photo-next fire put the cones in front of it. They are on wrong side away from peep hole in your photo. Mark Link to comment Share on other sites More sharing options...
Celia UK Posted November 16, 2015 Author Report Share Posted November 16, 2015 Thanks old lady - there's me thinking the smaller pieces are more vulnerable near the elements - you live and learn! Mark - yes I understand the theory but this hole takes my thermocouple, which I'd have to remove to look in. I did think about that when I did the second glaze firing in this kiln, but thought that taking out might mess things up and even then, am not sure what I would do as a result of what I could see the cones doing! I've been using the cones more as a check on how they relate to the temperature I've set on the controller. Thank you both! Link to comment Share on other sites More sharing options...
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