Joanie Berkwitz on thu 11 nov 10
Hi Clay buds! Happy Fall!
Is it possible to blend an earthenware slip with a white stoneware slip,
to create a casting slip that fires higher than ^04, and is stronger,
but doesn't have to go up to mid range? I'd like to bisque fire at
hotter than 04, but still have some porosity so that my 06 glazes will
work. Or is that just too hot for the talc ball clay? What book would be
best to read to understand about the properties of casting slips? Thank
you in advance for a response! Clayart rules! Joanie in Carlsbad
David Martin Hershey on fri 12 nov 10
Hi Joanie,
You're Back!
I'm certainly no expert on this, but here's my
wild-ass-experimentation 2 cents...
I've created "new" casting slips by blending
some existing slips to obtain different properties.
But I didn't try to change the temp range.
I haven't tried it, but Rosette Gault says that
low fire slip can be fired much higher just by
adding paper.
Of course, this doesn't help increase strength.
For mid fire, I've mixed Laguna 304 moroccan sand
with 965 white stoneware, and gotten a stronger
clay, with a nice body color, lighter than 304.
I've also mixed bmix slip with 965, and gotten a
body with better working properties than bmix,
but some of the nice color response of the bmix.
I'm just guessing, but I'll bet you could mix some
of your regular slip with 965, and "bisque" fire to
cone 1,2,or 3, and get a stronger somewhat absorbent
body that would still work with your low fire glazes.
Test different proportions, protect the test tiles
at first in case they melt. Keep good records.
Or you could test straight 965 fired to maturity ^4-5-6
and adjust your glazing techniques. Heating bisque
before glazing, adding binders etc. (965 is very strong)
You could also test firing 965 to ^1-3 for more absorption,
and see how strong it is, and if it's white enough for you.
Or you could find a strong cone 1 to 3 body that you like,
and make slip from it. (Vince has good instructions
on doing this on page 96 of his book.)
Unfortunately, I don't have any good book recommendations.
Val Cushing has some casting formulas, but they're for
mid to high fire slips. Lots of slip formulas in the archives
though. If you look at enough of them, you'll start to
understand how they work.
You could always pay Laguna $$$ to design you a slip,
but I think it would be more fun to do it yourself.
Call John Pacini at Laguna, and pick his brain.
Also, Ron Roy should have some insight.
Let us know what you discover.
Best, DMH
PS: Look in the archives for Charlie Cummings cone 1-3 body,
I dimly recall that there may be a casting slip formula too.
David Martin Hershey
DMH Studio + Design
2629 Manhattan Ave #137
Hermosa Beach CA USA
90254-2447 424.241.3809
http://www.dmhstudio.com/
http://www.obamacardgold.com
http://www.winetastingtrolley.com/
On 11/11/2010 2:15 PM, Joanie Berkwitz wrote:
> Hi Clay buds! Happy Fall!
>
> Is it possible to blend an earthenware slip with a white stoneware slip,
> to create a casting slip that fires higher than ^04, and is stronger,
> but doesn't have to go up to mid range? I'd like to bisque fire at
> hotter than 04, but still have some porosity so that my 06 glazes will
> work. Or is that just too hot for the talc ball clay? What book would be
> best to read to understand about the properties of casting slips? Thank
> you in advance for a response! Clayart rules! Joanie in Carlsbad
>
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