Ivor and Olive Lewis on thu 20 may 04
Dear Friends,
In "Ceramics" on p 55 Philip Rawson discusses the attainment of reduced =
effects. He proposes that "...One form or another of organic carbon may =
be added to the glaze to absorb oxygen from any oxides incorporated in =
it "
Knowing that opinion expressed among Clayart subscribers supports a view =
that organic carbon in clay should be avoided or respected by =
lengthening the mid temperature burn to discharge Carbon monoxide or =
dioxide to prevent future problems such as pinholing through outgassing, =
does anyone know of examples of "Organic Carbon" (which excludes such =
materials as Carborundum or Silicon carbide) being deliberately used as =
a glaze ingredient.
Or could Rawson be interpreting or assuming that reduction effects can =
be attributed to cases where a clayworker will add an adhesive such as =
Gum Acacia, or CMC to a glaze slop.
Any experience of this? Anyone ever done anything with this concept ? =
Any additional references known ?=20
Since there are no references nor a bibliography in the text, is this =
information trustworthy?
By the way, this is about Glaze, not "On Glaze" Resinate Lustre.
Best regards,
Ivor Lewis. Redhill, South Australia
wayneinkeywest on thu 20 may 04
Correct me if I am wrong (it wouldn't be the first time 8>), but
isn't ash a form of "organic carbon"?
Regarding the comment "...view that carbon in clay should be avoided
or respected..."
don't some wood firing folk try for "carbon-trapping", such as in
shino style glazes. Yes, I know that has more to do with reduction
and the fuel used in the kiln, but still carbon, and deliberately
introduced?
David, Tony, Mel, Luc, Merrie?
Wayne Seidl
Key West, Florida, USA
North America, Terra
Latitude 81.45W, Longitude 24.33N
Elevation 3.1 feet (1m)
----- Original Message -----
From: "Ivor and Olive Lewis"
To:
Sent: Thursday, May 20, 2004 1:41 AM
Subject: Rawson on Reduction.
Dear Friends,
In "Ceramics" on p 55 Philip Rawson discusses the attainment of
reduced effects. He proposes that "...One form or another of organic
carbon may be added to the glaze to absorb oxygen from any oxides
incorporated in it "
Knowing that opinion expressed among Clayart subscribers supports a
view that organic carbon in clay should be avoided or respected by
lengthening the mid temperature burn to discharge Carbon monoxide or
dioxide to prevent future problems such as pinholing through
outgassing, does anyone know of examples of "Organic Carbon" (which
excludes such materials as Carborundum or Silicon carbide) being
deliberately used as a glaze ingredient.
Or could Rawson be interpreting or assuming that reduction effects
can be attributed to cases where a clayworker will add an adhesive
such as Gum Acacia, or CMC to a glaze slop.
Any experience of this? Anyone ever done anything with this concept
? Any additional references known ?
Since there are no references nor a bibliography in the text, is
this information trustworthy?
By the way, this is about Glaze, not "On Glaze" Resinate Lustre.
Best regards,
Ivor Lewis. Redhill, South Australia
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Lee Love on thu 20 may 04
wayneinkeywest wrote:
>Correct me if I am wrong (it wouldn't be the first time 8>), but
>isn't ash a form of "organic carbon"?
>
>
>
My woodstove ash is. Much of the carbon is not burnt up at wood
stove temps. When I wash it, some of it comes out, but I only screen
to 30 mesh, so I keep a lot of carbon. If you sieve a couple days
after mixing the glaze up, you can take off some of the carbon that
swells after soaking up water.
>don't some wood firing folk try for "carbon-trapping", such as in
>shino style glazes. Yes, I know that has more to do with reduction
>and the fuel used in the kiln, but still carbon, and deliberately
>introduced?
>
>
Usually, you don't put wood ash in a shino glaze because the calcium
bleaches the iron out that gives the red color. I am specifically
thinking about putting ashing in one of my new shinos (Neph sye
substitution) because it is too metallic (Edouard, I will put up photos
soon! Promise! The Hiratsu subsitiution is gorgeous!)
--
in Mashiko, Japan http://mashiko.org
http://potters.blogspot.com/ Commentary On Pottery
Ivor and Olive Lewis on fri 21 may 04
Dear Wayne in Key West,
You are trying to trip me up ! !
If it is an ash, then all of the carbon should have been burned away,
or should be one is to get the maximum returns from the raw materials.
Yes, there may be residuals but the way Rawson speaks this is a
deliberate introduction to the Glaze Recipe.
My note about avoiding carbon was as an inclusion in the raw clay.
Some contain traces of lignite, others coal and there is always the
possibility of roots and humus in clays of surface origin.
Regarding Shino, this is a function of making a low temperature
reduction, so the carbon comes from the gas or the wood fuel. It is
not a art of the glaze formulation in a formal sense.
Rawson says "One kind or another of Organic Carbon" this rules out
Soot, Graphite, Diamond and as I said Silicon Carbide.
So Wayne, have you any ideas to solve the problem?
Best regards,
Ivor Lewis. Redhill, South Australia
Earl Krueger on fri 21 may 04
On Wednesday, May 19, 2004, at 22:41 US/Pacific, Ivor and Olive Lewis
wrote:
> Rawson discusses the attainment of reduced effects. He proposes
> "...organic carbon may be added to the glaze to absorb oxygen from any
> oxides incorporated in it
Ivor,
No experience here, but I'll have a go at conjecture.
If for "organic carbon" we used sugar, or perhaps starch
for a non-soluble component, we would find that these
materials start decomposing at a relatively low temperature.
Certainly before the inorganic components began to fuse
and seal the surface to oxygen penetration.
In an oxygen rich environment I would expect the carbon
and hydrogen to preferentially combine with the free oxygen
as opposed to reducing the oxides. Or, the oxides may be
reduced but would be re-oxidized before the glaze sealed
over.
In a neutral atmosphere there may be insufficient free
oxygen to completely oxidize the carbon and hydrogen
therefore the inorganic oxides may give up their oxygen
and not be re-oxidized, thus the reduction effect.
Since electric kilns without vent systems are reputed to
be neutral in atmosphere it seems plausible that one
may be able to achieve some reduction effects by this
method.
Tantalizing enough thought for some experimentation.
Earl K...
Bothell, WA, USA
daniel on fri 21 may 04
Hi Ivor,
So I was thinking either crushed charcoal or sawdust in the glaze slop when
I saw yours and Wayne's posts yesterday. My problem is, wouldn't it burn all
the carbon out before the glaze components got hot enough to reduce locally
? I also wondered vaguely about "gluing" plant matter to the pot before
glazing over it. I guess the melting point of the glaze would have relevance
here. Higher firing glazes might not work so well. Raku afterall uses
organic carbon, doesn't it ?
Very interesting idea.
Thanx
D
> Dear Wayne in Key West,
> You are trying to trip me up ! !
> If it is an ash, then all of the carbon should have been burned away,
> or should be one is to get the maximum returns from the raw materials.
> Yes, there may be residuals but the way Rawson speaks this is a
> deliberate introduction to the Glaze Recipe.
> My note about avoiding carbon was as an inclusion in the raw clay.
> Some contain traces of lignite, others coal and there is always the
> possibility of roots and humus in clays of surface origin.
> Regarding Shino, this is a function of making a low temperature
> reduction, so the carbon comes from the gas or the wood fuel. It is
> not a art of the glaze formulation in a formal sense.
> Rawson says "One kind or another of Organic Carbon" this rules out
> Soot, Graphite, Diamond and as I said Silicon Carbide.
> So Wayne, have you any ideas to solve the problem?
> Best regards,
> Ivor Lewis. Redhill, South Australia
>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
Thanx
D
Belmont, California, USA
(ex terra australis)
Ivor and Olive Lewis on sat 22 may 04
Dear Daniel,
Not sure that I can give an answer.
The whole idea of using something like Sawdust or any other organic
material in a glaze is new to me though I have considered using
Graphite. Until I read that passage in Rawson I had not even
considered it as an option.
I am wondering where he came across the concepts and if he has seen it
done.
I might add, reading his descriptions of the practical aspects of
production gives me the disquieting feeling that he has not experience
whatsoever as a potter or ceramic artist, which increases my unease
about what we might consider an authoritative text which has no
references.
Thanks for your thoughts and enjoy your weekend,
Ivor Lewis. Redhill, South Australia
Potters Council Member
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