Maureen Hicks on sun 21 nov 99
To Whom It May Concern:
I need some help regarding Porcelain slip.
I have just been given 4 gallons of porcelain slip to use for my Christmas
ornaments molds. The brand name is UltraSlip.
However, I have NEVER worked with porcelain slip, and do not know the first
thing about it.
Please send me information regarding its use, and how to clean, fire, glaze
etc. porcelain.
Thank you ever so much.
Maureen Hicks
John Rodgers on mon 22 nov 99
Mauree,
I worked with porcelain slip for many years. I have used Ceramichrome, Bells,
and a few others but my favorite was Coloriffic Porcelain Slip. Coloriffic is
made in a cottage industry in Lynette, Wa. Howard and Jeanette Gullikson were
the owners.
My experience with porcelain was that before casting, you would want to
establish the specific gravity and viscosity of the porcelain. A good starting
point for test casts would be with the viscosity at 45 sec, and the SpG @ 1.61.
This subject has been worked to death on this list, so I won't cover it here,
but if you have trouble, e-mail me off-list and I will go over it. Once you
have those parameters set, then do a few test casts to check the performance of
the porcelain.
When you pour the porcelain, use a picther with a "pointed" spout. Anything
else and you won't have fine control, and with porcelain you will want this.
Don't pour the porcelain straight down the mold. Direct the stream against a
flat surface in the mold.
In porcelain especially, DO NOT STOP pouring and then restart! If you do, you
will have a line in the finished piece.
Depending on the size of the piece you are trying to cast, leave the slip in
the mold long enough to form a 1/8th to 1/4in thick wall of clay, then turn up
and drain at an angle. If you turn the mold up vertically the vacumn induced by
draining may pull the newly formed clay shell from the mold. After initial
draining, turn upside down for drainage to complete.
Allow mold to sit until slip is leather hard in the mold. Knowing when to open
the mold is a matter of experience and will vary a bit, depending on the
weather, the mold condition, the thickness of the casting. I watch the
porcelain in the mold "Spare" ( the pouring opening) and when I see it begin to
loosen I will removed the mold bands, bump a mold half to loosen it, then
carefully attempt to lift straight up. If it doesn't come freely, I wait a
while and try again. Once one side is removed, the mold can be bumped again to
loosen the piece in it, then it can be carefully removed.
Green porcelain castings are very fragile and can easily be warped or cracked.
Dry porcelain greenware is so brittle it can be explosive. I always have new
studio help and students to sacrifice their first dry greenware casting by
squeezing it to the point of colllapse. It is always a revelation. I suggest
you try this yourself with a small piece that can be held in one hand. You will
learn a lot about porcelain in that one moment.
I you have any assembly work to do with porcelain it must be done while the
pieces are still green. and the greener the better. A mix of slip and vinegar
makes an excellent glue for the joined parts.
Store on plaster board. It helps the drying process.
After assembly and all has dried completely, using an exacto knife, carefully
scrape,carve, or otherwise chase away the casting seams. Then wash carefully
with a small sponge and water....commonly called cleaning. Carve back in any
detail washed away by cleaning, the re-touch with sponge.
Some high temp underglazes can be applied at this time......but very
carefully!!!
Now the greenware is ready to fire. Porcelain shrinks dramatically when fired
to temp.
BE sure the kiln shelves are coated with adequate kiln wash, and then
sprinkled with silica sand. This will accomodate the movement involved in the
shrinking and will negate any tendency to crack in the porcelain bases. Keep in
mind, however, that this is porcelain, and it will crack where it decides to,
regardless. Cracks will appear at times, and will be totally unexplainable.
Just accept it as the toll of the Kiln Gods, and go one with you business. Less
angst that way.
All the porcelain slip I ever worked with I fired to cone 6.
In my Alaska studio we specialized in original porcelain figurines and dolls,
using china paints for finishing the work. They were fired anywhere from cones
020 to 014, depending on the paint.
One last thing. If you will take a scrubbee, ie, the sponge with the medium
abrasive backing, and dry scrub the surface of the bisque porcelain, it will
finish with a velvet feel as smooth as a baby's behind.
Good luck.
John Rodgers
In Alabama
Maureen Hicks wrote:
> ----------------------------Original message----------------------------
> To Whom It May Concern:
> I need some help regarding Porcelain slip.
> I have just been given 4 gallons of porcelain slip to use for my Christmas
> ornaments molds. The brand name is UltraSlip.
> However, I have NEVER worked with porcelain slip, and do not know the first
> thing about it.
> Please send me information regarding its use, and how to clean, fire, glaze
> etc. porcelain.
> Thank you ever so much.
> Maureen Hicks
Bill Williams on mon 22 nov 99
I don't know if anyone else will answer, so I will try. Years ago, I made
porcelain dolls and so I will tell you what I remember. Pouring porcelain
is entirely different than the regular clay slip. For one thing the ceramic
slip will cause a mold to become pitted. So any mold you have used for
regular ceramic slip, will not work well with the porcelain. Porcelain
should be smooth, like silk. I can't remember how to time the slip before
pouring it out of the mold. You just need to watch the pour hole and when
it gets thick enough, pour it out. When you pour the slip into the mold,
you have to pour without stopping. If you stop, you will be able to see the
line on the piece. When you pour the slip out.........don't let it "glug".
Pour it out slowly and carefully, or your piece will pull away from the mold
on the inside. Strain the slip through a strainer and you can pour it back
into the original container. Set the mold on a pan, so the mold can drain
the rest of the slip out. When it is ready, very carefully remove the piece
from the mold. Porcelain is VERY fragile. Let it dry. I always fired my
porcelain to cone 18 before I cleaned it. Like I said, it is very fragile
and easy to break. If you fire it to a gold firing, it is easier to clean.
To clean the piece . (after the gold firing). Get it wet. Clean it wet. I
used a heavy nylon stocking. Use a magnifying glass to get it really
smooth. Then you have to put sand in your kiln and use kiln prop to keep
your pieces from collapsing or sagging. I can't remember the firing temp.,
but I think it is cone 6. When your piece is fired you use a light weight
sand paper to sand it smooth, smooth, smooth. Should feel like silk. Then
you can paint it with china paint. That is a completely different
technique as well. I don't know about glazes on porcelain. Someone else
may however. Connie
-----Original Message-----
From: Maureen Hicks
To: CLAYART@LSV.UKY.EDU
Date: Sunday, November 21, 1999 3:39 PM
Subject: Please Help RE: Porcelain slip
>----------------------------Original message----------------------------
>To Whom It May Concern:
>I need some help regarding Porcelain slip.
>I have just been given 4 gallons of porcelain slip to use for my Christmas
>ornaments molds. The brand name is UltraSlip.
>However, I have NEVER worked with porcelain slip, and do not know the first
>thing about it.
>Please send me information regarding its use, and how to clean, fire, glaze
>etc. porcelain.
>Thank you ever so much.
>Maureen Hicks
>
Maureen Hicks on tue 23 nov 99
Thank you so much for your reply.
You hit me right at home with your simple directions...as this whole
experience is all very very new to me. I do not understand the more complex
replies regarding the velocity etc of the slip. I just wanted to be able to
dilute the jar of slip that is so thick..it is like cream cheese thick. I
thought since it was given to me free of charge I would go ahead and try to
use it.
The only things that I am using the porcelain slip for are some Christmas
ornaments. I figured that should be simple and I should be able to do it. But
it is still so new to me. I love the idea of drying it in the kiln before
cleaning, thanks for sharing that with me.
I have one further question...Where do I find the sand that you refer to for
inside on the kiln shelf? I have never heard of this. I used regular kiln
wash in a thick coat, but that is all I knew for the regular slip.
Sincerely,
Maureen
John Rodgers on tue 23 nov 99
Maureen, something I forgot to mention. Get a small jiffy mixer....stainless
type, the one gallon size, and mix your slip in the 1 gallon jar. Then spread
the end of a ladies stocking over the wide mouth of the jar. Then lift the jar,
and pour the stocking and the slip into a pitcher. This strains the slip
removing any little contaminants. You need the fine-ness of the stocking to do
a good job. After squeezing the slip from it, wash the stocking for reuse in
the clay room.
Good luck
John Rodgers
Maureen Hicks wrote:
> ----------------------------Original message----------------------------
> To Whom It May Concern:
> I need some help regarding Porcelain slip.
> I have just been given 4 gallons of porcelain slip to use for my Christmas
> ornaments molds. The brand name is UltraSlip.
> However, I have NEVER worked with porcelain slip, and do not know the first
> thing about it.
> Please send me information regarding its use, and how to clean, fire, glaze
> etc. porcelain.
> Thank you ever so much.
> Maureen Hicks
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