Cindi Anderson on sun 19 oct 03
On ClayArt a while back I got the advice from many people to use my clay
body as the basis for decorating slip, then the clay and slip shrink
together correctly. But every "public" studio I go to has buckets/jars of
slip mixed up, which they use on a wide variety of clay bodies. And I
noticed that workshop presenters often use slip that doesn't match their
clay bodies.
So, are there slip formulas that are pretty forgiving, that work on a
variety of clay bodies? Or did I mis-interpret before. Maybe an all-over
slip that you would do decoration on top of needs to be more closely matched
than just a decorating slip that is used to make random brush strokes but
doesn't cover the whole area evenly?
Thanks
Cindi
Fremont, CA
Ababi on mon 20 oct 03
May be a dumb answer about slips.
It is not that simple.
There are some factors.
1) Wet on wet?
2)wet on dry, (bone, leatherhard)?
3) Wet on bisque?
I guess you mean the first one.
In this case the main point I think about is the shrinkage.
Porcelain over gorged might shrink too much.
You can try add defloculant might smooth, the slip over.
You can try an add of 5% borax or 10% frit to glue it while firing.
Vince has a wide range slip, see in his book. I think you might find
there some clever answer to your not dumb at all question.
Ababi Sharon
Glaze addict
Kibbutz Shoval Israel
ababisha@shoval.org.il
http://members4.clubphoto.com/ababi306910
http://www.matrix2000.co.nz/Matrix%20Demo/Ababi.htm
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Cindi
Anderson
Sent: Sunday, October 19, 2003 11:01 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Maybe a dumb question about slip
On ClayArt a while back I got the advice from many people to use my clay
body as the basis for decorating slip, then the clay and slip shrink
together correctly. But every "public" studio I go to has buckets/jars
of
slip mixed up, which they use on a wide variety of clay bodies. And I
noticed that workshop presenters often use slip that doesn't match their
clay bodies.
So, are there slip formulas that are pretty forgiving, that work on a
variety of clay bodies? Or did I mis-interpret before. Maybe an
all-over
slip that you would do decoration on top of needs to be more closely
matched
than just a decorating slip that is used to make random brush strokes
but
doesn't cover the whole area evenly?
Thanks
Cindi
Fremont, CA
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Snail Scott on mon 20 oct 03
At 02:01 PM 10/19/03 -0700, you wrote:
>...I got the advice from many people to use my clay
>body as the basis for decorating slip, then the clay and slip shrink
>together correctly. But every "public" studio I go to has buckets/jars of
>slip mixed up, which they use on a wide variety of clay bodies...
>So, are there slip formulas that are pretty forgiving, that work on a
>variety of clay bodies?
A slip made of only clay (the usual definition) will
fit best when applied to very wet clay of the same
composition. But many people apply slips to leather-hard
clay: a discrepancy in shrinkages already. And many
people like to work with red clays, but use white clays
for the basis of their slips so that colored slips will
be bright or glazes more luminous. Another discrepancy,
since the white clay probably doesn't match the red
clay exactly. This works OK, though, as long as the
clay is still a bit damp. The slip and clay stick
together pretty well and can cope with small differences
in shrinkage rates, I think partly because the clay
sucks the excess moisture out of the slip, equalizing
the moisture levels before it dries. The thicker the
slip application, the more any differences will start
to matter, but thin coatings can accomodate a lot.
Slips applied to dry (or bisque) ware cannot accomodate
such a large discrepancy, and tend to crack if applied
thickly. This is when engobes become useful. Non-plastic
ingredients can be added to reduce the shrinkage to
a level closer to that of the dry (or bisque) clay.
Of course, no wet slurry of anything is going to behave
exactly like dry clay, but with slips and engobes both,
'close enough' is sufficient. A wide range of slips can
be made to work on many clay bodies, and engobe and
glaze recipes can vary widely (though not infinitely)
and still stay on most clays. Clay is pretty forgiving
stuff, within limits.
So, although making slip from your regular clay is
often a good idea, usually foolproof and convenient
(especially if your clay is smooth and white), it's
not essential. Using other clays for decorating slip
may be necessary if your clay is dark or gritty.
Fortunately, this usually works just fine.
-Snail
Stephani Stephenson on tue 21 oct 03
of course the caveat... There's no such thing as a dumb
question!!!!
(although, when working at a ski resort I did have a guy,
who was standing at the bottom of a staircase ask me, as he
looked and pointed up the staircase...."Does this go up?")
Cindi
I will pass on a tip I got from Rudy Autio, and which has
worked for me on many occasions...
try using casting slip!
Buy it dry, then simply mix with water. Buy casting slip in
the color and temp range you desire..
for example I use to buy white cone 06 casting slip to
apply on darker clay and fire it slightly higher, to cone 05
to 03...
. you could also try cone 6 casting slip for higher temps,
etc. You can add colorants to the slip.
It worked beautifully for me on wet, dry and even bisque.
sometimes I would add a bit of frit if I needed more melt.
The slip is opaque and durable... in fact the 'crystal
swan' white I use to use was VERY opaque, possibly too
opaque for some purposes....did not let any underlying clay
show when mixed to heavy cream consistency.
The casting slip does not have the shrinkage problem of pure
clay slip and when purchased dry, is quite easy to mix and
use as needed.
I have also used E-22 from Chappell's book, and some other
slip/engobe recipes from that book may be helpful.
right now I use a buff clay and a red clay in the studio
and simply use one clay as a slip on the other when I need
either a dark slip on a light clay or vice versa.....I still
use the white casting slip on a dark red clay when I use
sgrafitto .
Stephani Stephenson
steph@alchemiestudio.com
Alycia Goeke on thu 23 oct 03
hi cindi,
i just went to a tom coleman workshop and he has a porcelain clay body that
he has developed. he says it will virtually fit with any clay body. It is sold
through aardvark. he mixes it up in a sunbean mixer that can be purchased at
walmart for under 20.00 bucks. he add 2 to 4% colorants and uses bottles found
in beauty supply places for hair color application. he also brushes it on. his
workshop was wonderful. if you ever get a chance to see him work, it is well
worth it!
happy potting,
alycia
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