Talbott on mon 8 dec 97
Can local reduction agents like SiC in a glaze recipe provide the same type
of reducing affect that firing in a gas kiln in a reducing atmosphere can
produce? I somehow strongly doubt it. What is your opinion or better yet
experience proven. ...Marshall
101 CLAYART MUGS
2ND ANNUAL CLAYARTERS' GALLERY - NAPLES, MAINE (Summer 1998)
E-MAIL ME FOR AN APPLICATION
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Celia & Marshall Talbott, Pottery By Celia, Route 114, P O Box 4116,
Naples, Maine 04055-4116,(207)693-6100 voice and fax,(call first)
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Karl P. Platt on tue 9 dec 97
SiC, in my experience is useless in electric kiln firing. Two results were
had:
A. Real bad pitting
B. No red
The original idea to use SiC came from Sevres. I'll leave it to you to go
fish-up the papers. They're in French
shelford on tue 9 dec 97
For what it's worth, I played around with SiC for awhile in various amounts,
got some quite attractive effects lightly sprinkled with red, but nothing to
fool anybody into thinking reduction. And of course, there is always the
frankenstein monster of foaming, lurking in the background of SiC use.
Sometimes the frankenstein effect is what you want, of course, but it makes
a weird mug.
- Veronica
>----------------------------Original message----------------------------
>Can local reduction agents like SiC in a glaze recipe provide the same type
>of reducing affect that firing in a gas kiln in a reducing atmosphere can
>produce? I somehow strongly doubt it. What is your opinion or better yet
>experience proven. ...Marshall
>
> 101 CLAYART MUGS
> 2ND ANNUAL CLAYARTERS' GALLERY - NAPLES, MAINE (Summer 1998)
> E-MAIL ME FOR AN APPLICATION
> http://fmc.utm.edu/~dmcbeth/cag/naples.htm
>
> Celia & Marshall Talbott, Pottery By Celia, Route 114, P O Box 4116,
> Naples, Maine 04055-4116,(207)693-6100 voice and fax,(call first)
> Clayarters' Live Chat Room, Fri & Sat Nites at 10 PM EDT & Sun at 1 PM EDT
> http://webchat12.wbs.net/webchat3.so?Room=PRIVATE_Clayarters
> ---------------------------------------------------------------------
>
>
___________________________________________
Veronica Shelford
e-mail: shelford@island.net
s-mail: P.O. Box 6-15
Thetis Island, BC V0R 2Y0
Tel: (250) 246-1509
Tom Buck on wed 10 dec 97
Marshall Talbot asked about using silicon carbide powder as a reducing
agent in an electric (oxidative) kiln firing. There was a discussion of
this topic 18 months ago (+/-) on Clayart, and one knowledgeable person
noted that particle size of the SiC powder was a critical factor, that
extremely sub-micron size was essential.
I first came across this notion of SiC local reduction in Sanders
text, Glazes for Special Effects. So I tried several firings, using a
rather coarse SiC powder. No success. The basic problem is finding SiC so
microfine that when it breaks down and releases carbon it does so where
you want it to happen, viz., right alongside a copper atom. If you can
obtain ultra fine SiC powder, then give it a try. Otherwise all you'll get
is a lumpy green. Peace.
Tom Buck ) tel: 905-389-2339
& snailmail: 373 East 43rd St. Hamilton ON L8T 3E1 Canada
(westend Lake Ontario, province of Ontario, Canada).
Rick Sherman on wed 10 dec 97
----------------------------Original message--------------------------
SiC, in my experience is useless in electric kiln firing. Two results
were had:
A. Real bad pitting
B. No red
The original idea to use SiC came from Sevres. I'll leave it to you to
go
fish-up the papers. They're in French
--------------------------response------------------------------------
Karl: Sorry your local reduction reds did not come out. I suggest you
read Herbert Sanders' text, Glazes for Special Effects. He got great
copper reds in a glo-bar kiln using SiC. One student, Dwayne Bentziene,
got his MFA making great reds with SiC. I have one myself. It is
important to use a fine [FFF grain] grind of SiC and don't add too
much. .2 to 1% is all you need. Also, plan for a long firing schedule.
If you want more information, e-mail me directly and I will add
details.
RS
San Jose, CA
PS: If you could ever get old copies of the Journal of the American
Ceramic Society, back in the 20's and 30's, they have descriptions of
how to get reds with SiC or by dripping oil on pots during firing.
LizzardOL on wed 10 dec 97
In my quick read of the CM article on oxidation copper reds, I remember that
the authors mention they use a very fine size of silicon carbide (they
describe it as 10 microns in size) that is not readily available except in
very large but unspecified amounts (gosh thanks). I've tried adding some of
what is available at my local supplier (comes in 36, 60, and 100 "grit" -
which I guess correlates to screen size) to a cone 6 copper red glaze and
tested it on white stoneware in oxidation in an electric kiln. What we got was
a pale green glaze with red blotches (presumeably where the particles of
silicon carbide were). We tried this glaze in reduction and got black craters
in a red glaze.
In a message dated 12/8/97 1:55:00 PM, you wrote:
<of reducing affect that firing in a gas kiln in a reducing atmosphere can
produce? I somehow strongly doubt it. What is your opinion or better yet
experience proven. ...Marshall
101 CLAYART MUGS
2ND ANNUAL CLAYARTERS' GALLERY - NAPLES, MAINE (Summer 1998)
E-MAIL ME FOR AN APPLICATION
http://fmc.utm.edu/~dmcbeth/cag/naples.htm
>>
John & Anne Worner on fri 12 dec 97
Hi!
If it's of any interest, I see in my catalog from Minnnesota Clay U.S.A.
that they
sell silicon carbide in a 500 mesh size. Their phone # is
1-800-CLAY-USA.
Anne and John Worner
Spring, TX where we have been hit by an Artic blast - brrrr!
LizzardOL wrote:
>
> ----------------------------Original message----------------------------
> In my quick read of the CM article on oxidation copper reds, I remember that
> the authors mention they use a very fine size of silicon carbide (they
> describe it as 10 microns in size) that is not readily available except in
> very large but unspecified amounts (gosh thanks). I've tried adding some of
> what is available at my local supplier (comes in 36, 60, and 100 "grit" -
> which I guess correlates to screen size) to a cone 6 copper red glaze and
> tested it on white stoneware in oxidation in an electric kiln. What we got was
> a pale green glaze with red blotches (presumeably where the particles of
> silicon carbide were). We tried this glaze in reduction and got black craters
> in a red glaze.
>
> In a message dated 12/8/97 1:55:00 PM, you wrote:
>
> <> of reducing affect that firing in a gas kiln in a reducing atmosphere can
> produce? I somehow strongly doubt it. What is your opinion or better yet
> experience proven. ...Marshall
>
> 101 CLAYART MUGS
> 2ND ANNUAL CLAYARTERS' GALLERY - NAPLES, MAINE (Summer 1998)
> E-MAIL ME FOR AN APPLICATION
> http://fmc.utm.edu/~dmcbeth/cag/naples.htm
> >>
Karl P. Platt on fri 12 dec 97
The title of this thread is ridiculous. Cu red is impossible in
oxidation.
> It is
> important to use a fine [FFF grain] grind of SiC and don't add too
> much. .2 to 1% is all you need. Also, plan for a long firing schedule.
> If you want more information, e-mail me directly and I will add
> details.
>
> RS
> San Jose, CA
>
>
> PS: If you could ever get old copies of the Journal of the American
> Ceramic Society, back in the 20's and 30's, they have descriptions of
> how to get reds with SiC or by dripping oil on pots during firing.
Sure SiC can work. However, SiC by its nature is one of the poorer
things one could use for a reducing agent. Mainly owing to its tendency
to evolve gas. I say ditch the carbon and use elemental Si -- it's cheap
and widely available. I have a hunk here on my desk -- I put it there
because Brasilians have this tendency to fiddle with things lying about
and it annoys me. Anyone who touches the Si chunk promptly gets very
dirty hands.
Fine particle size would give a couple things:
A. Better distribution of the material
1. it's heavy and if the grains are too large they'll sink in the
slip.
B. A statistically improved opportunity to reduce the Cu present.
I can think of 6 or 7 compositional factors which would make a
difference as well -- in terms o fdecomposition of the SiC, etc.
Most ceramic kilns are real leaky. Whether or not the glaze would be
reduced and remain reduced depends more on how tight the kiln is than
anything. I observe that the amounts of SiC suggested in the above quote
are widely variable, which affirms this supposition. there's a lot of
space between 0.2 and 1% -- by weight I assume.
I have the ACerS Journals going back to the early 1930's and a few
volumes of the Transactions of the ACerS much older than this -- thanks
to a few old timers I have had the pleasure to work with over the years.
A lot of wierd and clever things were tried and used to develop colors
and special effects -- one of my favorites are Hobart Kraner's
crystalline glazes based on sodium silicate. Look at the footnotes of
the papers relating to Cu red development through the use of SiC. These
papers are more interesting.
Lisa P Skeen on fri 12 dec 97
Hmmmm....what're the prospects of crushing this stuff with a mortar &
pestle? I've never seen it so I don't know.
Lisa Skeen, Living Tree Pottery and Soaps
http://www.uncg.edu/~lpskeen
On Wed, 10 Dec 1997 14:25:58 EST Tom Buck writes:
If you >can>obtain ultra fine SiC powder, then give it a try. Otherwise
all you'll
>get>is a lumpy green. Peace.
>
>Tom Buck ) tel: 905-389-2339
>& snailmail: 373 East 43rd St. Hamilton ON L8T 3E1 Canada
>(westend Lake Ontario, province of Ontario, Canada).
>
John Post on fri 12 dec 97
>It is
>important to use a fine [FFF grain] grind of SiC and don't add too
>much. .2 to 1% is all you need.
Here is a recipe from Emmanuel Cooper's book on glazes that I tried. It
did yield some reds but I wouldn't confuse them with copper reds from a
fuel kiln. Mine always resulted in reddish areas floating in the middle of
a light green background. (I don't know if the silicon carbide is hard to
disperse evenly in the glaze or if it moves away from the edges of the pots
during the firing.) The red areas were the color of raspberry preserves...
and my silicon carbide was extremely fine grain.
+++++++++++++++++++++++++
+++ Pale Pink 409 +++
+++++++++++++++++++++++++
Range: 6-8
Firing type: Oxidation
Glaze type: Stoneware
Color: Raspberry in some areas and light green
Surface: Gloss
Testing: Good
Date: 12/11/96
Kona F-4 2500 50 %
Whiting 750 15 %
Talc 300 6 % Hazard!
Zinc oxide 300 6 % Hazard!
EPK 350 7 % Hazard!
Flint 800 16 % Hazard!
-------- ------
5000 100 %
Tin oxide 50 1 %
Black copper oxide 50 1 % Hazard!
Silicon carbide 25 0.5%
Notes:
Works best over white bodies and the raspberry color that is caused by
the local
reduction from the silicon carbide is usually in the middle, not near the
edges.
Cost: $ 1.45 per kg glaze
$ 7.26 per 5000 g batch
===========================
Chemical Analysis
===========================
Na2O 0.14 Al2O3 0.31 SiO2 2.61
K2O 0.07 SnO2 0.02
MgO 0.13
CaO 0.44
CuO 0.03
ZnO 0.20
Alumina:Silica ratio is 1.00 : 8.29
Neutral:Acid ratio is 1.00 : 8.34
Alkali:Neutral:Acid ratio is 1.00 : 0.31 : 2.63
Expansion coefficient: 72.8 x 10e-7 per degree C
John Post
jp6mchp@moa.net
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