D. L. Engle on thu 1 may 08
Hi Kathy,
Since firing a piece can affect the surface texture, that should be a
consideration in the process. The shrinkage from greenware to bisque is
probably going to be too small to notice but depending on the type of clay
there could be a noticeable change in the surface. Of the types of clays
I've been working with, terra cotta is much less changed in this regard
after bisque. It retains is initial smoothness while others can become
slightly grainy. This effect is very slight but depending on the scale of
the piece could be a deciding factor.
I often make silicon molds off damp clay models. As long as there is no
standing water on the piece this offers the best surface fidelity. Also, no
sealers or releases are needed. In my circumstance the likely loss of the
model is not a concern as I now have a perfect mold.
Best Wishes, Debbie
D. L. Engle Sculpture
www.home.earthlink.net/~dlenglesculpture/
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG]On Behalf Of Kathy Forer
Sent: Monday, April 28, 2008 1:34 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: rubber mold on greenware
On Apr 28, 2008, at 8:35 AM, Snail Scott wrote:
> But first, why do you want to make the mold from
> greenware? Its chances for survival are vastly
> higher if you bisque it first. Seriously, I can't
> imagine any reason not to bisque first, especially
> if you want to preserve the pattern to fire later,
> because the odds of destroying greenware are
> really high.
Ever-practical, your question is helping me reconsider my desired
plans. I was hoping to make a mold before the piece went through final
firing shrinkage.
It's a fairly simple low to medium-relief piece with minimal undercuts
-- basically a blanket mold. It seems some of the silicon rubbers
don't require sealant, theoretically, that is.
But really, why take such a chance, why not fire the piece first? Good
question, thanks.
Kathy
--
www.kforer.com
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