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help with raku problem

updated tue 5 feb 02

 

ronn j.frank on sun 3 feb 02


Hi Cate. Clay Art Center in Tacoma, WA sells several of the common and some
uncommon raku glazes. Their email address is clayartcenter.com.
Also, the most common clear crackle glaze that I am aware of is 80%Gerstley Borate
and 20% Nepheline Syenite. Perhaps your local retailer could make it up for you.
Good Luck. Susan Frank

Cate Loveland wrote:

> I'm new to the list, and had planned to lurk a while more to get a better
> feeling of what the list is all about, but am sitting down, still smoky from
> a raku firing, with some burning questions.
> First, a brief intro...I'm Cate, living in Tucson, and fairly new to clay.
> The kiln gods surprised me a few years ago by depositing a used electric
> kiln on my doorstep (actually, my landlord brought it to me from an estate
> sale, saying..."I thought you might like this" and at $75, I figured the
> Universe was making a statement!) One thing has led to another, and I find
> myself blundering into all kinds of serendipities, including being accepted
> into a juried show and finding a gallery that likes (and sells!) my work.
> Which is currently handbuilt lidded bowls, with animal faces (wolves,
> coyotes, raccoons (Rocky Raku'n, oh, no!) forming the lids, slip and
> underglaze painted. Raku fired. (spouse, extremely supportive, built raku
> kiln)
> The problem: I ran out of my transparent crackle raku glaze, and the
> ceramics store sales person said that the Duncan GL (leaded) clear glaze
> would work for raku. Well, it didn't. It's still milky, long after the
> copper flash raku glaze had matured. These pieces take hours and hours to
> make, so I'd like to retrieve what I can. I figured I could fire the piece
> in the electric kiln to glaze maturity, which I presume would ruin the raku
> effect but retrieve the clear glaze...but then, can I refire the piece in
> raku again to get the copper flash back? What would that do to the clear
> glaze, if anything?
> And, can anyone recommend a a source for a commercially available
> clear raku glaze? I don't have scales or anywhere to store chemicals, and
> would prefer, since I'm working in a relatively small scale, to stick with
> commercially available stuff.
> Most replies I get to questions like this involve, "I dunno, try it
> and see," but I'm hoping that someone can give me an idea of what to expect.
> I"ve learned a lot in the week or two I've been lurking, and thank you
> all for your willingness to share.
>
> ______________________________________________________________________________
> 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.

Cate Loveland on sun 3 feb 02


I'm new to the list, and had planned to lurk a while more to get a better
feeling of what the list is all about, but am sitting down, still smoky from
a raku firing, with some burning questions.
First, a brief intro...I'm Cate, living in Tucson, and fairly new to clay.
The kiln gods surprised me a few years ago by depositing a used electric
kiln on my doorstep (actually, my landlord brought it to me from an estate
sale, saying..."I thought you might like this" and at $75, I figured the
Universe was making a statement!) One thing has led to another, and I find
myself blundering into all kinds of serendipities, including being accepted
into a juried show and finding a gallery that likes (and sells!) my work.
Which is currently handbuilt lidded bowls, with animal faces (wolves,
coyotes, raccoons (Rocky Raku'n, oh, no!) forming the lids, slip and
underglaze painted. Raku fired. (spouse, extremely supportive, built raku
kiln)
The problem: I ran out of my transparent crackle raku glaze, and the
ceramics store sales person said that the Duncan GL (leaded) clear glaze
would work for raku. Well, it didn't. It's still milky, long after the
copper flash raku glaze had matured. These pieces take hours and hours to
make, so I'd like to retrieve what I can. I figured I could fire the piece
in the electric kiln to glaze maturity, which I presume would ruin the raku
effect but retrieve the clear glaze...but then, can I refire the piece in
raku again to get the copper flash back? What would that do to the clear
glaze, if anything?
And, can anyone recommend a a source for a commercially available
clear raku glaze? I don't have scales or anywhere to store chemicals, and
would prefer, since I'm working in a relatively small scale, to stick with
commercially available stuff.
Most replies I get to questions like this involve, "I dunno, try it
and see," but I'm hoping that someone can give me an idea of what to expect.
I"ve learned a lot in the week or two I've been lurking, and thank you
all for your willingness to share.

Michael Imes on mon 4 feb 02


Hello Cate,

Regarding your questions about raku, since both bisque and raku are
usually fired to cone 06 you can refire a raku piece in an electric bisque
fire. Since the electric kiln is always oxidizing and the raku piece is
still porous any grey or black smoking effects will be burned off in the
oxidation. You will also see any copper reds or metallic lusters turn to
shades of copper green (usually). If you quench your raku pieces in water
make sure they're thoroughly dry before any refiring. If a glaze is
translucent (milky of foggy) it could be that it's a little under fired, in
which case you can refire it and try to get it hotter. If it's translucent
because that's it's mature look, refiring probably won't change it.

I encourage you to try mixing your own raku glazes. Here is a simple
recipe for clear crackle: 80% feldspar and 20% gerstley borate. I've seen
this glaze work as a clear using combinations of 80/20 (feld./Gerst. Bor.),
75/25 and 60/40. If you don't have a scale you can try bulk measurement,
i.e., 3 cups feldspar and 1 cup gerstley borate. You'll need some kind of
screen or a power mixer attachment for your drill to mix it and get the
lumps out (you can get this attachment at your local home supply store in
the paint section), but it's still worth the effort. Commercial glazes can
be very expensive and with them you're usually paying for water and the
shipping of water. If you have managed to build and fire your own raku
kiln, mixing a couple of simple glazes will be easy by comparison. If you
need more help or glaze recipes I'd be happy to send you a bunch onor of the
list serve. Between all of us on Clayart you can probably collect more
recipes than you can use. Blessings on your raku endeavors.

Sincerely,
Michael Imes


From: Cate Loveland
>Reply-To: Ceramic Arts Discussion List
>To: CLAYART@LSV.CERAMICS.ORG
>Subject: help with raku problem
>Date: Sun, 3 Feb 2002 20:46:12 EST
>
>I'm new to the list, and had planned to lurk a while more to get a better
>feeling of what the list is all about, but am sitting down, still smoky
>from
>a raku firing, with some burning questions.
>First, a brief intro...I'm Cate, living in Tucson, and fairly new to clay.
>The kiln gods surprised me a few years ago by depositing a used electric
>kiln on my doorstep (actually, my landlord brought it to me from an estate
>sale, saying..."I thought you might like this" and at $75, I figured the
>Universe was making a statement!) One thing has led to another, and I find
>myself blundering into all kinds of serendipities, including being accepted
>into a juried show and finding a gallery that likes (and sells!) my work.
>Which is currently handbuilt lidded bowls, with animal faces (wolves,
>coyotes, raccoons (Rocky Raku'n, oh, no!) forming the lids, slip and
>underglaze painted. Raku fired. (spouse, extremely supportive, built raku
>kiln)
>The problem: I ran out of my transparent crackle raku glaze, and the
>ceramics store sales person said that the Duncan GL (leaded) clear glaze
>would work for raku. Well, it didn't. It's still milky, long after the
>copper flash raku glaze had matured. These pieces take hours and hours to
>make, so I'd like to retrieve what I can. I figured I could fire the piece
>in the electric kiln to glaze maturity, which I presume would ruin the raku
>effect but retrieve the clear glaze...but then, can I refire the piece in
>raku again to get the copper flash back? What would that do to the clear
>glaze, if anything?
> And, can anyone recommend a a source for a commercially available
>clear raku glaze? I don't have scales or anywhere to store chemicals, and
>would prefer, since I'm working in a relatively small scale, to stick with
>commercially available stuff.
> Most replies I get to questions like this involve, "I dunno, try it
>and see," but I'm hoping that someone can give me an idea of what to
>expect.
> I"ve learned a lot in the week or two I've been lurking, and thank
>you
>all for your willingness to share.
>
>______________________________________________________________________________
>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.




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Karen Shapiro on mon 4 feb 02


Hi Cate,

For wonderful raku glazes, if you don't want to mix your own, Clay Art Center in Tacoma does a fantastic job. You can order dry or wet -- they have a website -- www.clayartcenter.com

I recommend them highly.

Karen in Gualala



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