Ron Roy on mon 1 jun 98
Hi Kathy,
Reduction is to be avoided with all bisque because - as the organics are
burning out (700C to 900C) they need to have access to oxygen (fresh air)
so any iron in the body will not be reduced to FeO with is a strong flux
and will help to over mature you clay at it's recommended top temp. Don't
go to fast during this stage - especially with a tight kiln and/or when
it's tightly stacked.
I think the recommended speed should be well under 100C per hour but again
- some clays have more carbon and other contaminants so they may need a
slower treatment. On the other hand - because there is little iron
porcelain type bodies - you will be able to go faster.
You can some times tell when there is reduction during the bisque because
the red lower firing cones will look reduced and will drop faster than
usual - you are all firing with large cones aren't you?
No - I am not working for Orton - but cones are basic for firing - at any temp.
>----------------------------Original message----------------------------
>
>Hi All--
>
>Thanks to everyone who was so nice about answering my obviously dumb
>question about if you could bisque in ox and glaze in reduct. I have done
>pottery for quite awhile, but unfortunately was never exposed to reduction
>firing. It just made sense to me that if you have a gas kiln you would do
>both bisque and glaze in it. Why have one just to do bisque---guess
>there's still alot to learn!! Another thing that perplexed me and led to
>my question is that if almost everyone bisques in ox (except the weird
>ones!) why would clay supply companies show bisqued chips in both
>reduction and oxidation? Now you can see my confusion---do potters ever
>bisque fire in reduction and then glaze in ox???? Since I have always
>done both firings in ox--well except for raku--this is all virgin
>territory to me!!
Ron Roy
93 Pegasus Trail
Scarborough, Ontario
Canada M1G 3N8
Tel: 416-439-2621
Fax: 416-438-7849
Web page: http://digitalfire.com/education/people/ronroy.htm
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