Monica Wright on fri 28 jan 11
so... what is best way to acheve low shrinkag claybody???=3DA0 No wierd mat=
er=3D
ials either.=3DA0 Lots of grog is easily done but what else?=3DA0 Can i exc=
hang=3D
e some calcined kaolin for some epk or is that completely absurd?=3DA0 peop=
le=3D
will probably flip out when they see the body i am currently using.=3DA0 B=
as=3D
ically i took the equl parts porcelain body -kaolin, ball clay, flint, feld=
=3D
spar and added another equal part of glodart and about 5-7% grog.=3DA0 Work=
s =3D
great, nice and white.=3DA0 Fine by my standards.=3DA0 I have a friend who =
want=3D
s a low shrinkage white body for sculpture.=3DA0 All i can think of is calc=
in=3D
ed kaolin.=3DA0 thanks.
=3DA0
-Steve (not Monica)
Snail Scott on sat 29 jan 11
On Jan 28, 2011, at 9:17 AM, Monica Wright wrote:
> so... what is best way to acheve low shrinkag claybody??? No wierd =3D
materials either. Lots of grog is easily done but what else?=3D20
Shrinkage is almost entirely a matter of particle size;=3D20
that's why grog and sand work so well. Coarser clays,=3D20
like fireclay, have lower shrinkages than ball clay=3D20
precisely because of particle size. Of course, plasticity=3D20
is intimately tied to particle size, too, so I can't think of=3D20
any good way to reduce shrinkage without also=3D20
reducing plasticity. As a handbuilding sculptor, though,=3D20
that's fine by me! I can't stand a highly plastic clay=3D20
body. My current clay has less than 5% shrinkage,=3D20
due to lots and lots of grog. When I make my own=3D20
clay, I use about 30% grog by volume.=3D20
Grog is not all created equal, though. Multiple grog=3D20
sizes will make for a more workable body than just all=3D20
one size. Big grog makes the biggest reduction in=3D20
shrinkage, but smaller grog can be added in larger=3D20
quantities, and superfine powdery grog (still hundreds=3D20
of times bigger than any clay particle) will allow for=3D20
good working properties and still have a huge effect=3D20
on shrinkage.=3D20
Calcined materials also have an effect on shrinkage=3D20
reduction, though because the particles are still clay-
sized, it is less noticeable than even fine grog.=3D20
Plasticity? Who needs it? Pffffththttt!
-Snail
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