Stephen Grimmer on sat 5 may 01
Bruce,
Howzabout "White Earthenware?" In my book, to be fairly called
porcelain, the stuff has to be vitrified. I know this can easily get in to
an argument of semantics (and has in the past!), but Raku firing a stoneware
(or porcelain) body doesn't make it stoneware, it makes it Raku ware.
Since I'm feeling a bit pedantic, some argue that porcelain must be
white, vitreous, translucent, must ring when tapped, and have no ball clay
added (i.e. only kaolin, feldspar, and flint). I could go a step further and
say porcelain must consist of only Kao-lin and Petuntze! I take a more
relaxed stance, and allow ball clay and a fair bit of grayness before my
feathers are rankled. Heck, I even have a body for Guan-type work that I
call "Black Porcelain," though it is really neither black nor porcelain.
Close on both counts, though. That body does go to show that good blue
celadons are possible (better!) on bodies that contain considerable Iron.
Best,
Steve
--
Stephen Grimmer
Southern Illinois University at Carbondale
> From: Bruce Girrell
>
> Subject: Re: Laboratory Stuff Auction Site
>
> OK, I know "porcelain raku" is an oxymoron, but I don't know what else
> to call it. Anyone have a better suggestion than "white firing, fine
> grained, grog free, thermal shock resistant clay body"?
vince pitelka on sun 6 may 01
> Howzabout "White Earthenware?" In my book, to be fairly called
> porcelain, the stuff has to be vitrified. I know this can easily get in to
> an argument of semantics (and has in the past!), but Raku firing a
stoneware
> (or porcelain) body doesn't make it stoneware, it makes it Raku ware.
Steve -
Thanks for this. I agree that there is no such thing as a porcelain raku
body, and no such thing as low-fired porcelain. It does not become
porcelain until it is vitrified above cone 8. A midrange white body can be
called a porcelaineous stoneware or a white stoneware or a midrange
whiteware, but not porcelain. At low temperatures it is whiteware or white
earthenware, although I have always thought the latter seemed like an
oxymoron, since earthenware has always implied native low-fire clays which
are generally high in iron. I know that vocabularly evolves over time, but
porcelain has always been something very specific and special, and I
advocate keeping it that way.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
vince pitelka on mon 7 may 01
> I'm trying to come up with a clay body that is as smooth and white as
> porcelain, yet can withstand the thermal shock inherent in horsehair
> decoration. This is even more severe than raku work, since the raku war=
e
is
> protected by the reduction chamber as it cools through the quartz
inversion
> point, whereas the horsehair piece is exposed to air currents and other
> uneven cooling during that critical time
Bruce -
Have you tried the old standby 50-50 talc/ball clay body? With that much
talc it has very high thermal shock resistance. It makes a great raku bo=
dy,
and I expect it might work very well for your process.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
Bruce Girrell on mon 7 may 01
Stephen Grimmer wrote:
> Howzabout "White Earthenware?" In my book, to be fairly called
> porcelain, the stuff has to be vitrified.
I understand. And that's why I put that disclaimer at the end saying that
"porcelain raku" is an oxymoron.
White stoneware doesn't quite do it for me because my experience with white
stoneware is that it is way grittier than a porcelain body. Also, "stoneware
raku" is just about as bad as "porcelain raku".
I'm trying to come up with a clay body that is as smooth and white as
porcelain, yet can withstand the thermal shock inherent in horsehair
decoration. This is even more severe than raku work, since the raku ware is
protected by the reduction chamber as it cools through the quartz inversion
point, whereas the horsehair piece is exposed to air currents and other
uneven cooling during that critical time
I have made several different clay bodies for test. Some are just Great
Lakes Clay's porcelain raku body with either wollastonite or pyrophyllite
added. Others have been made from scratch, using no free silica. The flint
serves no purpose since the pieces are never fired to vitrification and it
can only cause problems at the quartz inversion. I have not had an
opportunity to test fire the "built from scratch" clay bodies yet, though.
I welcome any suggestions from anyone about how to approach this problem.
Bruce "can't you just leave things alone?" Girrell
Marta M. Gloviczki on tue 8 may 01
hello,
i follow this topic with interest. i do both raku and low fire salt firings
and i`d like to know how should i call the fired pot, when i use grolleg
porcelain clay. i understand that since my claybody is not fired in high
temperature, i should not call it porcelain.
so, what are those forms i made out of porcelain clay body, saggarfired to
cone 02 or rakufired to cone 06?
sometimes i fire them in my electric kiln to cone 6.
if the name "porcelain" referes only to the end-product, what about
stoneware and earthenware?
cheers,
marta gloviczki
http://www.mypots.com/Marta.htm
http://www.silverhawk.com/crafts/gloviczki/welcome.html
Ababi on tue 8 may 01
I am a bit entering without reading it all.So sorry if write off subject.
In V.C.'s book there is a recipe to kind of raku porcelain. . It works. I=
t
has a lot of alumina and some molochite as grog. I made it with unplastic
kaolin, this is what I have, was very hard to use but I make slip out of =
it
to cover my raku , whitening it and hope, like the last time I have done =
it
would give me nicer crackles. it is good with oxides or stain, for
decorating too.
Ababi Sharon
ababisha@shoval.ardom.co.il
http://members4.clubphoto.com/ababi306910/
http://www.milkywayceramics.com/cgallery/asharon.htm
----- Original Message -----
From: "Bruce Girrell"
To:
Sent: Monday, May 07, 2001 6:38 PM
Subject: Re: Porcelain Raku Body
> Stephen Grimmer wrote:
> > Howzabout "White Earthenware?" In my book, to be fairly called
> > porcelain, the stuff has to be vitrified.
>
> I understand. And that's why I put that disclaimer at the end saying th=
at
> "porcelain raku" is an oxymoron.
>
> White stoneware doesn't quite do it for me because my experience with
white
> stoneware is that it is way grittier than a porcelain body. Also,
"stoneware
> raku" is just about as bad as "porcelain raku".
>
> I'm trying to come up with a clay body that is as smooth and white as
> porcelain, yet can withstand the thermal shock inherent in horsehair
> decoration. This is even more severe than raku work, since the raku war=
e
is
> protected by the reduction chamber as it cools through the quartz
inversion
> point, whereas the horsehair piece is exposed to air currents and other
> uneven cooling during that critical time
>
> I have made several different clay bodies for test. Some are just Great
> Lakes Clay's porcelain raku body with either wollastonite or pyrophylli=
te
> added. Others have been made from scratch, using no free silica. The fl=
int
> serves no purpose since the pieces are never fired to vitrification and=
it
> can only cause problems at the quartz inversion. I have not had an
> opportunity to test fire the "built from scratch" clay bodies yet, thou=
gh.
>
> I welcome any suggestions from anyone about how to approach this proble=
m.
>
> Bruce "can't you just leave things alone?" Girrell
>
>
_________________________________________________________________________=
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>
Gary Elfring on tue 8 may 01
>I'm trying to come up with a clay body that is as smooth and white as
>porcelain, yet can withstand the thermal shock inherent in horsehair
>decoration. This is even more severe than raku work, since the raku ware=
is
>protected by the reduction chamber as it cools through the quartz invers=
ion
>point, whereas the horsehair piece is exposed to air currents and other
>uneven cooling during that critical time
Great Lakes Clay sells a "White Grogless Raku" clay, which I use for all =
my
horsehair work. Works perfectly- pure white, and it withstands the shock =
of
going straight from the kiln to a piece of kiln shelf to be decorated. I =
glaze
the inside of all my work, so I fire to 1800 F then pull the piece.
I think their web address is:
http://www.greatclay.com
-gary elfring-
the horsehair and feather king
http://www.elfring.com/pottery
vince pitelka on wed 9 may 01
> i follow this topic with interest. i do both raku and low fire salt
firings
> and i`d like to know how should i call the fired pot, when i use grolleg
> porcelain clay. i understand that since my claybody is not fired in high
> temperature, i should not call it porcelain.
Marta -
With the cone 6 firings I think you are close enough to high-fire to call it
sagger-fired porcelain. Technically I think true porcelain should be fired
to high-fire temperatures (at least cone 8). The raku work should not be
called porcelain. I would call it either whiteware or low-fire. I think it
is perfectly okay to say it is made from a porcelain claybody, but not to
call it low-fired porcelain or porcelain raku.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
Lana Reeves on wed 9 may 01
Hi-- I've done some horsehair raku. I use a white stoneware body with a =
little fine porcelain grog [called molochite] wedged in. When it's bone =
dry, apply terra sig & burnish. Bisque only to ^010. This gives a =
beautiful surface for the horsehair. I haven't had any break yet.
Lana in Somerville, MA
kilnkat@rcn.com=20
friedlover on wed 9 may 01
Great Lakes clay in Illinois sells a "Porcelain Raku" clay that fits your
needs exactly; it is so white that it looks bisqued when it isn't, and even
feels bisqued and that strong when it's still green. It throws beautifully.
Clay Coordinator on wed 9 may 01
Bruce,
I have got a great Porcelain Raku Body.
I think it is from Nicholas Bernard. It was in an old CM, but I forgot the
date.
The parts recipe is:
EPK -150
OM-4 -60
Wollastonite - 25
Talc - 5
Macaloid -1
Grog 50
Mix with 1 gallon of cider vinegar and age.
It is a great white body. I use fine/medium grog. You can up the macaloid
if you like to 2 parts. It has served me well.
Thanks,
John Britt
Penland Clay Coordinator
Bruce Girrell on wed 9 may 01
My thanks to all who have responded on this thread.
To those who have suggested Great Lakes Clay porcelain raku body - That's
what we are currently using. There are good days and bad days. Recently, we
lost 3/4 of our G.L. Clay porcelain raku pieces during the decoration
firing. Didn't lose any of the G.L. Clay white raku pieces. Very
disheartening. There is so much time in these pieces up to that point. The
white raku handles the shock, but looks so gray and lumpy compared to the
porcelain raku pieces. The smoke effects also look dirty on the white raku,
while they look beautiful on the porcelain clay.
The G.L. Clay porcelain raku has the physical properties of whiteness and
texture that I want, but just is not taking the thermal shock. I am
currently amending the G.L. Clay porcelain raku with wollastonite and
pyrophyllite. The pyrophyllite is winning so far, but we haven't gotten to
fire very many of the test pieces.
To those who have suggested alternative clay bodies - I have saved your
messages and I will add these to my list of tests to run. Thank you for your
input.
About the name - The issue has been pretty well addressed, but for those who
hold to the "it's not porcelain unless it's fired to vitrification" point
of view, just what do you call the greenware of the thing that ends up being
porcelain?
My primary issues center on the color, texture, and thermal shock
resistance. The only thing so far that has given me the color and feel that
I want is what gets labeled porcelain. Unfortunately, we are still losing
way too many pieces to cracking during decoration. Secondary issues are
"feel" while throwing, trimming qualities, and how the clay takes the iron
chloride colorant.
I'm still plodding through the experiments. It will take time.
Bruce "maybe if I added shredded support hose?" Girrell
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