Fabienne McMillan on sun 29 aug 10
Geetings,
I was wondering if there is any information or are any articles out
there on what constitute a good casting slip, what to shoot for and
what to avoid, how to troubleshoot one, how to formulate one? I've
been coming up pretty empty handed in my search so far; nothing but
vague information as to how to make one :( I would be targeting cone
6 and specifically a white, porcelaneous casting slip.
Thank you,
Fabienne
"We never touch people so lightly that we do not leave a trace." ~
Peggy Tabor Millin
John Rodgers on sun 29 aug 10
Fabienne,
I don't make my own slip from scratch, so can't really answer your
questions, but I have considered it often. I do use Cone 6 slip - both
porcelain and stoneware. I buy my stoneware slip in 50# bags. I have not
been able to find a suitable porcelain slip I can buy dry-bagged, but
would surely love to.
I use C5 B-mix from Laguna Clay, both as a plastic throwing clay, and as
a dry-bagged slip. I use these two together because they are so close in
composition that I can mix and match thrown parts and pieces with
slip-cast parts and pieces. I have found that that slip made from the
B-mix throwing clay does not make a good slip that works well. I have
found this to be true with other clays as well. I even bought dry-bagged
Standard C6 porcelain - the ingredients usually used in their throwing
porcelain which is a very fine throwing porcelain - but as a slip it
was terrible. So, until I can find a proper dry-bagged porcelain - I
have resigned myself to ready made wet slip - usually sold in 1 gallon
containers. Pricey, but I'm stuck with it for the moment. I would dearly
love to get my hands on a formula for a good, white, translucent
porcelain slip that I could mix myself.
RE: the Laguna B-mix - I talked with Laguna in 2005 aobut the slip vs
the throwing clay, because i had a HUGE project for which I wanted to
use the B-mix. At that time I was told that the B-mix slip formula was
different from the B-mix throwing clay. It was not disclosed to me, but
I think the big difference is in the amount of ball clay between them.
Throwing clay on the one hand has to be very plastic, and the slip on
the other hand has to be very short - ie, for example a porcelain slip
cast piece when dried for 20 minutes or so after being removed from a
mold, should not bend but should crack and break. This is an example of
how a "short" clay sould be, and slip should be short, not plastic. A
plastic clay does not give it's water up readily, a short clay does, and
this relates to the about of ball clay present, I believe.
On the issue of the water and ball clay, perhaps others more
knowledgeable - Vince P. and others - can weight in here and correct any
mistakes in my assumptions and add further to this. Water absorption
from the clay in a mold is a very important issue for slip casters, and
having a clay wit the wrong chemistry and physical properties can create
a lot of headaches.
Regards,
John Rodgers
Chelsea, AL
On 8/29/2010 12:39 PM, Fabienne McMillan wrote:
> Geetings,
>
> I was wondering if there is any information or are any articles out
> there on what constitute a good casting slip, what to shoot for and
> what to avoid, how to troubleshoot one, how to formulate one? I've
> been coming up pretty empty handed in my search so far; nothing but
> vague information as to how to make one :( I would be targeting cone
> 6 and specifically a white, porcelaneous casting slip.
>
> Thank you,
>
> Fabienne
>
> "We never touch people so lightly that we do not leave a trace." ~
> Peggy Tabor Millin
>
>
John Britt on mon 30 aug 10
"Mold Making And Slip Casting ", Andrew Martin.
John Britt
www.johnbrittpottery.com
ivor and olive lewis on mon 30 aug 10
Dear Fabienne McMillan,
Seek out the following comprehensive review of formulating both Clay bodies
and Glazes.
James Chappell, "The Potter's Complete Book of Clay and Glazes".
ISBN 0-08230-4202-2.
Chappell provides slip recipes for the major clay body classifications with
specific instructions for getting the best low viscosity mixture of clay
minerals and water that will drain quickly after being poured into the
mould.
Regards,
Ivor Lewis,
REDHILL,
South Australia
Jeff Jeff on tue 31 aug 10
Hey Fabienne,
When I first started slip casting I was of the frame of mind that I needed
to mix my own. I looked in every pottery book I could find and I tried
several. I finally settled on a recipe used by Dorothy Hafner in New York.=
I
found her recipe to be very user friendly. She was profiled, in Ceramics
Monthly, in the mid 80's.
I can't recall the ingredients and proportions, per se, but I know it used
#6 Tile and Kaopaque as its porcelain and Old Mine 4 as its ball clay.
I stopped mixing my own when I had to close down the studio a few years
later. (so its been awhile)
Does the Don Frith mold making book have a casting body listed in it? A
neighbor had bought it and for some reason I remember hearing about RT
Vanderbilt at the same time. RT makes defloculants and they were pushing th=
eir
latest, Darvan 811. (Their other defloculant is Darvan 7.) Darvan 811 is
thought to be the better defloc to use when mixing porcelain slip.
Mixing porcelain slip is a challenge. I wish you luck.
Jeff Longtin
Minneapolis
In a message dated 8/29/2010 2:00:04 P.M. Central Daylight Time,
clayart@ATT.NET writes:
Geetings,
I was wondering if there is any information or are any articles out
there on what constitute a good casting slip, what to shoot for and
what to avoid, how to troubleshoot one, how to formulate one? I've
been coming up pretty empty handed in my search so far; nothing but
vague information as to how to make one :( I would be targeting cone
6 and specifically a white, porcelaneous casting slip.
Thank you,
Fabienne
"We never touch people so lightly that we do not leave a trace." ~
Peggy Tabor Millin
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