Michael Plein on wed 28 feb 01
I resend this message, because until now no-one has found an answer to my
question.
Hello,
>
> Has someone expirience with "self-reduction" glazes? Is it possible to
> achieve local reduction effects in glazes and engobes for simulating a wood
> fire in electric kilns under oxidation atmosphere?
> My aim is to rebuild 11th century german ceramic. The old german used an
> engobe, made of red clay with flux (I think beechwood-ash) or a simplyfied
> terra sigillata (red clay with deflocculant leaved undisturbed for one day).
> Both works well at Segers cone 6a (1200 deg Cel) building a semimatt
> surface.
> At the moment I experiment with adding amounts of Carbon or SiC to an
> engobe.
>
> Perhaps someone can give me usefull hints.
>
> Thanks
>
> Michael
> Germany
Ababi on wed 28 feb 01
Hello Michael!
I sent you a letter off list because I had sent some letters to the list and
did not think I should repeat.
You can buy Lana Wilson's book and there you will find answer for both
questions.I do not copy from books, especially when they are available.
In my site you can see exercises I made of both subjects.
I offered you my glaze, because most of my materials and frit are coming
from Germany and probably you can find them. Perhaps you do not get answer
because the local reduction is very tricky story.
Ababi in Israel
ababisha@shoval.ardom.co.il
http://members4.clubphoto.com/ababi306910/
----- Original Message -----
From: "Michael Plein"
To:
Sent: Wednesday, February 28, 2001 8:54 PM
Subject: reduction effects under oxid. conditions
> I resend this message, because until now no-one has found an answer to my
> question.
>
>
>
> Hello,
> >
> > Has someone expirience with "self-reduction" glazes? Is it possible to
> > achieve local reduction effects in glazes and engobes for simulating a
wood
> > fire in electric kilns under oxidation atmosphere?
> > My aim is to rebuild 11th century german ceramic. The old german used an
> > engobe, made of red clay with flux (I think beechwood-ash) or a
simplyfied
> > terra sigillata (red clay with deflocculant leaved undisturbed for one
day).
> > Both works well at Segers cone 6a (1200 deg Cel) building a semimatt
> > surface.
> > At the moment I experiment with adding amounts of Carbon or SiC to an
> > engobe.
> >
> > Perhaps someone can give me usefull hints.
> >
> > Thanks
> >
> > Michael
> > Germany
>
>
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iandol on thu 1 mar 01
Dear Michael Plein,
When I saw your first posting I wondered whether or not this referred to =
Salt Glaze although your historic time frame seemed to refer to an =
earlier period.
I have no direct answer to your question. However, reduction is not well =
understood by potters who insist that it must take place within a =
atmosphere of carbon monoxide or free carbon, or in the presence of =
hydrogen. The only exception they allow is where Silicon carbide is one =
of the additives put in the glaze to cause local reduction.
A second problem concerns the idea of simulating wood fire. This can =
infer many things. Ash which floats through a kiln and is deposited to =
melt as temperature reaches extreme heat, flame marks due to tunnelling =
and restricted flow of flames and hot gas, local effects of reduction =
where additional wood is pushed through ports to rest against the pots =
are just a few of the alternatives which might be inferred from your =
post.
Although the idea of introducing carbon or silicon carbide seem =
attractive, may I suggest you try to find a source of elemental silicon =
powder which a fine grain size. Though not popularly recognised as such, =
this is a strong reducing agent at the temperatures you intend working. =
Another thought is to work in saggars and fill the bottom of each with a =
layer of graphite or activated charcoal. Since there is only nominal gas =
movement in an electric kiln the carbon will adsorb oxygen from air in =
the saggar and if this is not replace you will have a potentially =
reducing environment.
Best regards,
Ivor Lewis, Australia
Lili Krakowski on fri 2 mar 01
I would guess no one answered because Ceramics Monthly--and I would guess
Ceramic Review and lots of other magazines have had articles over the
years that discuss reduction in electric kilns. CM had one recently.
I certainly would consult Emanuel Cooper's book on electric kiln firing.
Then I would test test test. Using silicon carbide in a slip has worked
for me when I was testing this years and years ago.
However while there is debate on the topic, I stick with the notion that
silicon carbide is bad for electric kiln elements. T
alk to you dealer.
Lili Krakowski
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