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Bisque & Glaze Firing at the Same Time


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#1 Mossyrock

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Posted 01 February 2013 - 01:34 PM

I generally work with low-fire clay (Highwater's Stans Red). I currently bisque-fire to cone 04, then glaze-fire (majolica mostly) to cone 05. However, some pieces are decorated with a wash of Velvet Underglazes with no glaze. Can I fire bisque fire to cone 05 instead of cone 04 and have some of the velvet washed bisqued pieces in the same firing? What about bisque firing to cone 05 and having some bisqued majolica-glazed pieces in the same firing?
Brenda Moore
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#2 neilestrick

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Posted 01 February 2013 - 05:55 PM

You can fire everything to your glaze firing cone all at once. The only danger is if a piece getting bisqued blows up and gets on your glazed pieces. Best to put bisque pots on bottom shelves, glaze pots up top.
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#3 JBaymore

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Posted 01 February 2013 - 06:01 PM

Certain colors are sensitive to stuff like sulphur dioxide often generated by bisquing operations of high sulphur raw clays or by slight levels of reduction cause by the burning of organics from "dirty" raw clay bodies. So if you happen to be using those and don't have great local pickup airflow.... you could see some color shifts.

The most problematic are cadmium/selenium reds. (un-encapsulated)

best,

...............john
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#4 Benzine

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Posted 01 February 2013 - 07:42 PM

Yeah, as Neil said, the biggest problem, would be the bisque fired wares exploding, and sticking to the glaze fired wares.

That is why, I try to avoid combining loads of my student works. I swear, every time I try and toss a couple greenware projects in with some glaze, they end up exploding, getting small pieces on some of the glazeware. This is even if, I try to be cautious and put them on different levels. I apparently haven't paid enough tribute to the Kiln Gods.
"Anything worth believing, is worth questioning"

#5 Marcia Selsor

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Posted 02 February 2013 - 09:53 AM

Sometimes the fumes or gases from the raw clay can muddy the colors of glazes as John mentioned.
Possibly a vent may help avoid this, but I can't say for sure. I never had a vent when I fired the combined bisque and glaze firings.


Marcia

#6 Mossyrock

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Posted 02 February 2013 - 07:05 PM

Thanks for the info. My kiln is vented and to date, I've not had anything blow up during a bisque firing (knock on clay) so I'm going to give it a try at my next firing. I'm not a high production potter so being able to fire both glazed and greenware together should help me get finished work out quicker.
Brenda Moore
Mossy Rock Creations
High Point, NC

#7 TJR

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Posted 02 February 2013 - 07:19 PM

Mossyrock;
The only colours of glaze that I have noticed are affected by being next to greenware are commercial red glazes. They come out a nasty liver coloured brown. When I am firing my class work, I try to separate glaze from bisque, but it's often unavoidable to have two half loads, one of bisque and one of glaze. I now use commercial glazes which mature at cone 06, so I put the greenware in the bottom of the kiln, then the glaze stuff higher up. I have rarely had anything blow up, but when it does, man, those shards go EVERYWHERE! I say, "Go for it!", and I NEVER say that. Good luck.
TJR.




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