Joan Fink on tue 3 sep 96
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Name:Joan & Stanley Fink
E-mail: sfink@netvision.net.il
Date: 03/09/96
Time: 17:18:41
This message was sent by Chameleon
-------------------------------------
I am seeking formulae for crater glazes which do not contain
cryolite which is unobtainable here in Israel.
Joan Fink at sfink@netvision.net.il
PJLewing@aol.com on thu 5 sep 96
The usual way of obtaining craater glazes is to put silicon carbide into the
glaze. To do artificial reduction using silicon carbide, you use less than
1% and use the finest powder you can find. I would imagine that any more
than that, and any powder coarser than about 100 mesh would produce craters.
If you can't find silicon carbide at a pottery store, try abrasives
companies. They use it as a polishing agent, and would probably give you a
pound or so, which would probably last you a lifetime.
Good luck,
Paul Lewing, Seattle
http://digitalfire.com/magic/lewing.htm
Bruce Scheer on mon 9 sep 96
I must have missed the original question about crater glazes. Are these
used in oxidation for a reduction affect? Do I add silicon carbide to any
glaze recipe and is it dinnerware safe?
PJLewing@aol.com on tue 10 sep 96
Bruce,
Silicon carbide is used for two things.
First, in very small amounts to get reduction effects in oxidation, typically
from copper. I've tried, and never been successful, to reduce iron this way.
I've never heard of anyone else doing it either. Has anyone else out there
done this?
Second, to produce crater glazes. Amounts of silicon carbide above about 2%,
or of coarse grit, will produce bubbling over the whole surface. No, they
are not dinnerware safe, they are barely safe to handle. The craters are
usually large and very sharp-edged.
Paul Lewing, Seattle
You Name on tue 10 sep 96
Glazes with the characteristics of pinholes, craters, or anything of that
nature aren't safe for dinnerware. Food or other materials get into these
spaces and can't be cleaned out. Not a good idea!
Daniel W Kirkland on sat 23 aug 97
I just saw a piece with a cone 9 crater glaze on it. The only thing that
I was told was that crater glazes need silicon carbide. But I don't know
the trick to create a crater glaze using silicon carbide. Does anyone
have any information regarding these glazes? And does anyone have any
formulas for these glazes?
Thank you for any ideas or information that you have.
Bill Aycock on sun 24 aug 97
Silicon Carbide is used for "local reduction", and in the process, the
silicon part takes up Oxygen to make SiO2 (silica, or flint) and the Carbon
part takes up Oxygen to make CO2, which is a gas- therefore- BUBBLES !!.
Depending on the time-at-temperature, and the viscosity of the glaze, you
can get a foam glaze, or, if the bubbles get together to make big bubbles,
which then break- Craters.
Have fun- test- try-experiment- go for it! (a ready source of silicon
carbide for tests is the local car parts store, where they call it valve
grinding compound- get the water based kind- not the oil based)
PS- if the result you get is a foam- the glaze will "sing" to you as you
handle it, for a while.
At 09:08 AM 8/23/97 EDT, you wrote:
>----------------------------Original message----------------------------
>I just saw a piece with a cone 9 crater glaze on it. The only thing that
>I was told was that crater glazes need silicon carbide. But I don't know
>the trick to create a crater glaze using silicon carbide. Does anyone
>have any information regarding these glazes? And does anyone have any
>formulas for these glazes?
>
>Thank you for any ideas or information that you have.
>
>
Bill- busy on Persimmon Hill- watching a cat sleep next to the keyboard.
Bill Aycock --- Persimmon Hill --- Woodville, Alabama, US 35776
--- (in the N.E. corner of the State) ---
also -- W4BSG -- Grid EM64vr
baycock@hiwaay.net
Andrew & Laura Conley on sun 24 aug 97
Silicon carbide can be used in small amounts (0.5-1%) for local
reduction in oxidizing environments. I have never had great luck with
this - just small pinkish areas in a copper glaze. Silicon carbide can
also be used for crater glazes. For this it can be used at 20-30%. I
expect more and less can also work. I have seen this written in a glaze
book (which one?), and I have also seen the results of another potter's
work who did this.
Daniel W Kirkland wrote:
>
> ----------------------------Original message----------------------------
> I just saw a piece with a cone 9 crater glaze on it. The only thing that
> I was told was that crater glazes need silicon carbide. But I don't know
> the trick to create a crater glaze using silicon carbide. Does anyone
> have any information regarding these glazes? And does anyone have any
> formulas for these glazes?
>
> Thank you for any ideas or information that you have.
Paul Lewing on wed 27 aug 97
Took me a while to get to this message since I was off backpacking
again, at the world's most beautivful beach.
You can make almost any glaze into a crater glaze at almost any
temperature if you add enough silicon carbide of coarse enough grit.
Just do a line blend.
Paul Lewing, Seattle
BCTanz on sun 7 sep 97
Check the book about glazes that Robin Hopper wrote several years ago. He
has a chapter on crater glazes, along with a few formulas.
Maggie Woodhead on sun 10 feb 02
Hello and Kia Ora,
There is a friend in our group who makes dragons
and is finding it difficult to get a handle on the glazes she would like to use
on them. Has a whole lot all made and ready to fire.
What she would like to get is glazes with the sort of rough slightly under fired
and bumpy look. Crater glazes perhaps which I have not much idea about.
The question we are asking is what ingredients can be added to a glaze to give
this type of finish. She has tried crackle and raku type glazes but would like
something a little more rough looking rather than these which while they craze
are still smooth and have a melted look. Any ideas welcome.
We have tried beach sand, surprisingly this has quite a lot of melting material
in it.
The temperatures of the glazes she has are about cone 9 but since they do not
need to be fired to vitrification, underfiring may help. I think about cone 6
might be good. I am intrigued by her dilemma as it is outside my knowledge of
glazes and I would love to help. Looking for all the things we usually avoid
like the plague!
Thanks Clayarters in advance, Yours in anticipation
Regards and ----Best Wishes Maggie----
maggiew@clear.net.nz
Martin Howard on sun 10 feb 02
Silicon Carbide is the stuff to use.
It makes a horrible mess when you want a smooth surface:-)
Martin Howard
Webbs Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
01371 850 423
martin@webbscottage.co.uk
http://www.webbscottage.co.uk
Updated 8th February 2002
Paul Lewing on sun 10 feb 02
Maggie,
you can make just about any glaze into a crater glaze by adding silicon
carbide to it. If you want to do artificial reduction using silicon carbide
and get a smooth surface, you need to use less than about 0.5% of a VERY
fine powder, say 500 mesh or finer. Any more than that, or any coarser a
grind, will produce craters every time.
Paul Lewing, Seattle
Ababi on mon 11 feb 02
From the many tests I have done with Sic 1200# down or up to 100# I
found that the last, gives me nice craters in 1% of the glaze
Ababi Sharon
Kibbutz Shoval- Israel
Glaze addict
ababisha@shoval.org.il
http://members4.clubphoto.com/ababi306910/
http://www.milkywayceramics.com/cgallery/asharon.htm
http://www.israelceramics.org/
---------- Original Message ----------
>Maggie,
>you can make just about any glaze into a crater glaze by adding silicon
>carbide to it. If you want to do artificial reduction using silicon
>carbide
>and get a smooth surface, you need to use less than about 0.5% of a VERY
>fine powder, say 500 mesh or finer. Any more than that, or any coarser
>a
>grind, will produce craters every time.
>Paul Lewing, Seattle
>________________________________________________________________________
>______
>Send postings to clayart@lsv.ceramics.org
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>settings from http://www.ceramics.org/clayart/
>Moderator of the list is Mel Jacobson who may be reached at
>melpots@pclink.com.
dan mc kinnon on tue 12 feb 02
to: ababi
i'm interested in your comment about crater glazes,
are you talking about raku glazes; have been searching
for some crater type raku glazes --- if they are, can
you share formula's ... many thanks .... dan
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m markey on tue 12 feb 02
Hi Maggie!
Crater glazes can provide a very rough, sometimes sharp-edged texture to a
glazed surface. I don't recommend a "cratered" surface to something that is
to be touched, lifted, or otherwise handled often. Indeed, it would be a
fine texture for an object that is decorative in nature, and gets placed in
a permanent display case, but if one is to touch or handle the object, use a
smoother glaze.
Nonetheless, you asked for a glaze recipe for a crater glaze. The ones I
have used successfully contain cryolite. They are fired to mid-range cones
(4-6), and require experimentation while firing, for the desired results.
These two recipes are from the CM Handbook (1977), "Ceramic Glazemaking," by
Richard Behrens, and are amongst many crater glazes (some with extinct or
hard-to-find ingredients) found on pages 43 and 44:
Behrens Crater Glaze 5 (Cone 4-6)
Fluorospar--19%
Cryolite--34.3%
Kaolin (EPK is best)--9.0%
Flint--37.7%
Behrens Crater Glaze 10 (Cone 4-6)
Fluorospar---14.6%
Cryolite--26.3%
Kaolin (EPK)--21.0%
Flint--38.1%
Enjoy!
Best wishes!
Mohabee NakedClay@hotmail.com
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m markey on tue 12 feb 02
Maggie,
Another idea to create the rough surface your friend wants, is to use
strands of copper wire on the piece. I use scrap electric wire, plastic
coating removed, for this purpose. With a wire-cutting pliers, I add
"snippets" of wire into a glaze mixture, and brush the glaze onto the piece,
or dip the ware into the glaze. Stir often, since the copper wire will sink
to the bottom of the glaze container!
Caveat: make sure that the copper strands are 1/4" above the kiln shelf
surface. Liberally coat your kiln shelves with "white wash" before firing
with copper wire!
Best wishes!
Mohabee NakedClay@hotmail.com
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Martin Howard on wed 13 feb 02
a wire-cutting pliers, I add "snippets" of wire into a glaze mixture, and
brush the glaze onto the piece, or dip the ware into the glaze. >
A simpler way of adding this kind of material into a glaze is to collect the
swarf from a key cutter. Just sieve it to what fineness you want and add to
the glaze.
You could experiment with various grades of Silicon Carbide SiC at the same
time.
Won't be using it on my table ware though!
Martin Howard
Webbs Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
01371 850 423
martin@webbscottage.co.uk
http://www.webbscottage.co.uk
Updated 8th February 2002
Lois on mon 18 mar 02
I have been working on crater glazes for about 18 months, finally got them to work
like I want!
Very unpredictable. If anyone is interested I have some posted on a free
website.
Take a look and I welcome any comments.
http://www.absolutearts.com/portfolios/s/sharppots/
Lois in NC, two days of glorious spring then winter rain returned today.
Anne-Marie Yerks on sun 27 jul 08
Hi Everyone,
I have some old commercial glazes I bought on Craigslist -- hundreds of 2 oz
jars I got for $10. It's fun to try them out and experiment. Most of them
work perfectly in spite of being about 20 years old.
I used one yesterday called "White Crackle." It's a Mayco glaze. I used it
on some very large beads and when I opened the kiln, I found that the glaze
had not only bubbled, but also brought out some sort of grey grit. It looks
really good on the pieces and I want more of it. But my bottle is very
small. . . I think something is "wrong" with the glaze, so even if I buy a
new White Crackle from Mayco, I won't get the same results.
So, my question is -- does anyone know of a low-fire glaze (preferably
commercial, but I guess I could mix it on my own) that makes pinholes and
grit? Any suggestions appreciated!
Thanks,
Anne-Marie
amyerks (at) comcast [dot] net
Kim Hohlmayer on mon 28 jul 08
Hi Anne-Marie,
When I first started in ceramics 20 years ago while I was learning about high fire I was making money to buy equipment by making jewelry using low fire commercial glazes and under glazes. The lava style glazes should still be available from any of the major low fire glaze companies like Duncan, Mayco or Gare. Look for local hobby ceramic shops. All these companies have web sites too though I don't know the addresses. If that doesn't work I am sure that some hobbiest somewhere has old bottles hanging around. If all else fails, or if you like to mix your own there are recipes for them. I also just remembered that Laguna has some great low fire glazes that are lava like. Hope this helps. --Kim H.
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