Scott Paulding on sun 12 sep 04
Hello,
I've heard rumors about glazes that are so called self-reducing glazes,
that will reduce even in an electric kiln. I was wondeing if there was
validity to any of this, or I was listening to someone who likes to tell
fish stories.
I beleive they said it involved silicon carbide in the glaze, but other
than that I don't know...
Thanks,
-scott
=====
"I should have been a plumber."
-Albert Einstein
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Ama Menec on sun 12 sep 04
Hi Scott,
I've used a 'self-reducing' glaze in the past, from Emmanuel Coopers book,
using silicon carbide. It was supposed to be a copper red, but in fact looks
rather like lumpy raspberry sorbet. It's on a small porcelain tea bowl I
made as a student, and it's so sweet I still have it. The main problem was
getting the silicon fine enough, even the stuff that's sold as fine silicon
carbide is too coarse. I spent 1/2 a day just grinding it up in a mortar and
pestle, and it still wasn't fine enough. I think this is why I got the
raspberry sorbet effect. Fun to try 'tho.
Ama Menec, Totnes, Devon.
----- Original Message -----
From: "Scott Paulding"
To:
Sent: Sunday, September 12, 2004 9:28 PM
Subject: self reducing glazes
> Hello,
>
> I've heard rumors about glazes that are so called self-reducing glazes,
> that will reduce even in an electric kiln. I was wondeing if there was
> validity to any of this, or I was listening to someone who likes to tell
> fish stories.
>
> I beleive they said it involved silicon carbide in the glaze, but other
> than that I don't know...
>
> Thanks,
>
> -scott
>
> =====
> "I should have been a plumber."
> -Albert Einstein
>
>
>
> __________________________________
> Do you Yahoo!?
> Yahoo! Mail - 50x more storage than other providers!
> http://promotions.yahoo.com/new_mail
>
>
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daniel on sun 12 sep 04
Hi Scott,
Certainly this can be done. SiC has two effects that I know of in glazes.
One is reduction of the type you describe, for which it needs to be ground
very finely. The other is that it will cause cratering, a useful effect for
crater/volcano glazes.
I have no real experience with it except one very unreliable copper red. I
wouldn't blame that on the SiC though.
Robin Hopper mentions it in The Ceramic Spectrum. Hamer and Hamer describe
its use in more detail. They state that SiC breaks down into Si and C at
about 1000 C (1832 F) and the C goes after the O in the glaze releasing CO
and CO2. The gases bubble through the glaze and head for the flue. They call
the process autoreduction.
It seems 200 mesh or finer for autoredux(and very little of it) and 50 to
150 mesh for craters.
Thanx
D
Bonnie Staffel on mon 13 sep 04
Hi Scott,
You probably will get a lot of responses to this. Yes, silicon carbide is
commonly used as a reducing agent. I have made some beautiful copper red
glazes on porcelain with this method. You might search the archives of
Clayart for some recipes, or look in your glaze books.
I show a bowl that I made at Cranbrook with the copper red and purple glazes
on my website http://webpages.charter.net/bstaffel/potterygallery.htm The
other copper red glazes shown in that photograph were low fire smoke
reduction in an electric kiln. If I get to working in porcelain again, I am
sure I will make these glazes.
Warm regards,
Bonnie Staffel
http://webpages.charter.net/bstaffel
http://www.vasefinder.com/
Potters Council member
Tig Dupre on tue 14 sep 04
-------------------------<>-------------------------------I've heard rumors about glazes that are so called self-reducing glazes,
that will reduce even in an electric kiln. I was wondeing if there was
validity to any of this, or I was listening to someone who likes to tell
fish stories.
I beleive they said it involved silicon carbide in the glaze, but other
than that I don't know...
-------------------------<>-------------------------------
Scott,
Not a fish story at all! The use of small amounts of silicon carbide in electric fire, neutral atmosphere glazes provides a "local reduction." I have not yet achieved a really good copper red using this method, but I am working hard at it.
As usual, check the archives for recipes.
Tig Dupre
in Port Orchard, Washington
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