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Overfired glaze


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#1 bciancio

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Posted 06 June 2012 - 10:56 AM

The cone on my kiln sitter cone did not melt, and I toasted everything. Can it be saved?

#2 icyone

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Posted 06 June 2012 - 01:56 PM

We need some more info, maybe even photos to be able to help

#3 Marcia Selsor

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Posted 06 June 2012 - 02:32 PM

Are you sure you used the correct cone?
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#4 bciancio

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Posted 06 June 2012 - 02:58 PM

Yes, I'm positive. I only have cones for 4, 5, and 6, and the glaze would have been ok for cone 5 or 6.

Anyway, the pieces that survived in an acceptable form are just really brittle, crusty, dry. I was firing Amoco Ancient Jasper, Firebrick, Indigo Blue, Paladium, a Great lakes Speckled Blue, and I think it is Spectrum Textured Navy. I also had a Vert Lustre jar in the bottom that is fine, except its a little dark and has a real even tone. One bowl with Ancient Jasper looks interesting and I wonder if I can salvage it. It came out evenly toned deep dark red, but it has a charred texture. Do you think I could fire it again (with a witness cone) using a clear glaze over it?

The Speckled Blue came out in similar condition, but the Textured Navy I put over it just looks like smears of burnt dark grey carbon. Paladium and Indigo Blue are pretty hopeless looking. The piece is oK, but the glaze also looks like burnt dark grey carbon, and the Paladium also kind of bubbled.

I'm just wondering if I can turn this into a happy mistake or am I wasting my time?

#5 neilestrick

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Posted 06 June 2012 - 04:18 PM

Sounds more like it underfired, especially if the cone didn't melt. If it overfired everything would have puddled. Fire them again. Maybe you didn't have the timer set high enough?

Putting a clear over a glaze will not seal it off. It will likely make it run more and totally change the appearance. It's not like putting a clear glaze over underglazes, which do not melt and flow.
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#6 bciancio

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Posted 06 June 2012 - 04:28 PM

Sounds more like it underfired, especially if the cone didn't melt. If it overfired everything would have puddled. Fire them again. Maybe you didn't have the timer set high enough?

Putting a clear over a glaze will not seal it off. It will likely make it run more and totally change the appearance. It's not like putting a clear glaze over underglazes, which do not melt and flow.



#7 bciancio

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Posted 06 June 2012 - 04:33 PM

Sounds more like it underfired, especially if the cone didn't melt. If it overfired everything would have puddled. Fire them again. Maybe you didn't have the timer set high enough?

Putting a clear over a glaze will not seal it off. It will likely make it run more and totally change the appearance. It's not like putting a clear glaze over underglazes, which do not melt and flow.



#8 bciancio

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Posted 06 June 2012 - 04:35 PM

Well, that makes sense . . . It just seemed to take longer than usual. I will try it again tomorrow morning and report back! Thank you soooooo much for your responses!

#9 neilestrick

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Posted 06 June 2012 - 04:59 PM

Well, that makes sense . . . It just seemed to take longer than usual. I will try it again tomorrow morning and report back! Thank you soooooo much for your responses!


Could be the elements are wearing out, or one is burned out, or a connection has gone bad. With the kiln empty, put it on high and let it run until the elements start to glow. Very carefully open the lid just enough to see if all the elements are glowing. If all are glowing, and the firing is slower than usual, then they are probably worn out.
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