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#1
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Opinion - Bisque Firing Cone 06 or 04
We have always bisque fired to cone 06. One of the potters has suggested
firing to cone 04 to help eliminate various glaze problems. Any opinions on this? |
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#2
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Not sure what glaze problems you were experiencing, but for most of my
stuff 06 has worked fine. I used to bisque at 04 until one time I think I over-fired a little and the clay lost so much of its porosity that it was difficult getting glaze to adhere to it; that's why I only go to 06 now and it is fine for my high fire and raku. Two exceptions come to mind. Some teachers I've known (like my high school teacher) bisqure students' pots at 04 so that it is less vulnerable to breakage while glazing. Another exception is low-fire ware. If you look at the label of many commercial low-fire glazes they say to bisque at 04, even though the subsequent glaze-fire is only to 05 or 06. |
#3
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"Eric" wrote in message oups.com... Not sure what glaze problems you were experiencing, but for most of my stuff 06 has worked fine. I used to bisque at 04 until one time I think I over-fired a little and the clay lost so much of its porosity that it was difficult getting glaze to adhere to it; that's why I only go to 06 now and it is fine for my high fire and raku. Two exceptions come to mind. Some teachers I've known (like my high school teacher) bisqure students' pots at 04 so that it is less vulnerable to breakage while glazing. Another exception is low-fire ware. If you look at the label of many commercial low-fire glazes they say to bisque at 04, even though the subsequent glaze-fire is only to 05 or 06. We were getting bubbling in a Gerstley based glazed (Erin's base) that had been acting fine. I suspect that the Gerstley is changing with each order. One potter suggested that we try firing at a higher bisque. The studio is meant for students at the University and they have little or no experience so I was not sure if the decreased porousity would be harder or easier on them. It is interesting to hear that the higher bisque can benefit them. We have actually been trying to replace our glazes that have Gerstley which is what I think is probably the issue. //************************************************** ********* Erin's White - BaseHM = 35 Bentonite 100 Gerstley B 3200 Flint 3000 Talc 2000 Soda Spar F4 1400 EPK (Kaolin) 500 10100 Green Copper Carb 200 |
#4
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"DKat" wrote in message ... We have always bisque fired to cone 06. One of the potters has suggested firing to cone 04 to help eliminate various glaze problems. Any opinions on this? [We were having pinholing problems in low-fire ware (not just Gerstly Borate glazes). Firing the bisque to a maturity as high or higher than the glaze helped eliminate the holes. I think these clays contain something volatile that outgasses at peak temperatures, and makes its way out through the molten glaze. On the other hand, the body was marginally less absorbant of glaze, if that's an issue.] Andrew Werby www.computersculpture.com |
#5
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"DKat" wrote in message ...
We have always bisque fired to cone 06. One of the potters has suggested firing to cone 04 to help eliminate various glaze problems. Any opinions on this? 04 fires it to maturity (or should if your kiln reaches the proper temp.) for best results the bisque firing should be done 2 cones higher than the glaze firing. the extra time and cost is minimal but the result is a whole lot better, eliminating some of the blips that can happen otherwise. |
#6
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Jedi wrote: We were getting bubbling in a Gerstley based glazed (Erin's base) that had been acting fine. I suspect that the Gerstley is changing with each order. One potter suggested that we try firing at a higher bisque. The studio is meant for students at the University and they have little or no experience so I was not sure if the decreased porousity would be harder or easier on them. It is interesting to hear that the higher bisque can benefit them. We have actually been trying to replace our glazes that have Gerstley which is what I think is probably the issue. //************************************************** ********* Ah ha! Gertley Borate (aka "colemanite" I think?) I've been hearing for a few years to start watching out for inconsistent gerstley coming from the mine, which I think is somewhere in California. I continued using it with no bad results so I started thinking it might be a "Paul is dead" sorta thing. I guess they were right, whoever "they" are. I'll bet you are right in thinking its the gerstley. But I am no glaze chemist. BTW -- the 06 bisqueware that took the gerstley fine often had a glaze on it that was almost all gerstley: the 80/20 clear crackle raku glaze that you see everywhere. Good luck! Eric SpunMud |
#7
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P.S.: by the way, when i mentioned that some people i know have
bisqued students' pottery a little higher, to cone 04, in order to reduce breakage during "glazing," i just meant the process where the bisqueware is touched, decorated, dipped and generally handled during the glazing process -- not the glaze firing itself. the higher bisque fire results in a more stout piece of ware that can better withstand "rough" handling. sorry for being a bit vague there. |
#8
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"Eric" wrote in message oups.com... P.S.: by the way, when i mentioned that some people i know have bisqued students' pottery a little higher, to cone 04, in order to reduce breakage during "glazing," i just meant the process where the bisqueware is touched, decorated, dipped and generally handled during the glazing process -- not the glaze firing itself. the higher bisque fire results in a more stout piece of ware that can better withstand "rough" handling. sorry for being a bit vague there. I thought that was pretty clear. We have on occasion had the kiln underfired due to error and had a lot of breakage because the person unloading did not know the difference or didn't care. A sore point with me since I feel protective of the students. |
#10
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I agree Particularly for Earthenware
"DKat" wrote in message ... We have always bisque fired to cone 06. One of the potters has suggested firing to cone 04 to help eliminate various glaze problems. Any opinions on this? |
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