Last week we did a 1280º firing mainly for tile tests. The kiln has had
14 firings so it should be at its optimum. I use a fairly good controller which, the suppliers tell me, is very accurate. On this occasion we also used cones 8,9 & 10 to test heatwork. The result was that all three cones were all the way down and there was warping amongst the tiles which should have been good for the temperature. The controller has a automatic cutout and will flash a retrospective warning if the kiln overfires - this didn't happen. The cycle used was 100ºC/hr to 200º then full power to 1280º then a 15min soak. My supplier told me to try aiming for a lower temp with a longer soak. The next planned firing was a 1250º so I programmed 100º/hr to 600º then full power to 1240º (10º lower) then a 30 min soak. I put cones 8 and 9 on the middle shelf to test heatwork and the result was that both cones were, again, all the way down. The ware, on this occasion, including a terracotta with a firing range up to 1250º, stayed stable with no visible distortion. Is it plausible that 9+ can equate to a 1240º firing, as in the above example or is there something wrong with the controller? We're getting a bit desperate here as we've got our first market at the end of November and without an accurate kiln we're up a goat's ass without a paddle! Helpthanks again pete
(For those of you in the UK who know Potterycrafts we are using a P5976
4cub.ft Topworker with an Ipco 3000 controller.)