Kate Johnson on mon 29 nov 04
was Re: Re: Speaking of plaster... bats
Hi John--well, silly me! You answered my question, obliquely I think...
>
> The Pure and Simple system from Axner uses a drive key that you attach
> to the wheelhead using the bat pin screws. It is a positive drive and
> does not rely on frinction to drive the bat as does the Jeppson setup.
> Slippage simply does not occur on the Axner setup. Also, changing the
> bats as you work is done with the greatest of ease.
>
I wasn't actually talking about a bat you use on the wheel, since I
handbuild--for the most part the whole issue of pins and centering and
fitting to the wheel is moot, for me. I just want the old fashioned bats to
dry things on that I remember as a kid.
It isn't generally an issue, cutting the work free from the bat, either, but
if I make press or hump molds with plaster it _is_ necessary to think about
freeing the clay from the mold.
I'm thinking, logically, that if I make a press mold, the clay will shrink
and come loose from the plaster on its own. If I drape clay OVER a mold
I'll need to remove it before it gets leather hard because it will shrink
and crack, perhaps...
Time to check our archives again, eh? I do have one book, meant for
beginning potters, that I got some years ago that addresses making molds of
this sort...the thing is that we ask the list because the members may have
had a different experience or a personal epiphany.
So again, thank you, and sorry I wasn't clear enough in my query!
Best--
Kate
claybair on mon 29 nov 04
wasRe: Speaking of plaster...bats
Kate,
Get some Hardibacker 1/4 inch at your local
home supply store. This is the stuff used under tile in the
bathroom or flooring. You just score and snap it
to whatever sizes you need.
It's a cement product and will wick moisture away
from the clay. There are several surfaces available
smooth, rough and a grid pattern.
I use these exclusively as ware boards and have been
using them with my molded platters. The only issue is that
it can get heavy and a bit cumbersome when flipping. I haven't
worked a system out for that yet.
They take up much less space than wood as they are only 1/4" thick.
Gayle Bair
Bainbridge Island, WA
http://claybair.com
-----Original Message-----
From: Kate Johnson
I wasn't actually talking about a bat you use on the wheel, since I
handbuild--for the most part the whole issue of pins and centering and
fitting to the wheel is moot, for me. I just want the old fashioned bats to
dry things on that I remember as a kid.
It isn't generally an issue, cutting the work free from the bat, either, but
if I make press or hump molds with plaster it _is_ necessary to think about
freeing the clay from the mold.
I'm thinking, logically, that if I make a press mold, the clay will shrink
and come loose from the plaster on its own. If I drape clay OVER a mold
I'll need to remove it before it gets leather hard because it will shrink
and crack, perhaps...
Snip>
Best--
Kate
John Rodgers on mon 29 nov 04
was Re: Re: Speaking of plaster... bats
Kate Johnson wrote:
> I'm thinking, logically, that if I make a press mold, the clay will
> shrink
> and come loose from the plaster on its own. If I drape clay OVER a mold
> I'll need to remove it before it gets leather hard because it will shrink
> and crack, perhaps...
Kate, your assumptions are quite right. Press clay to the inside fo a
mold and it comes free as it dries and shrinks. Drape over the mold and
it wil shrink, drawing in tight against the mold, and cracks will occur.
If you watch really closely, you can make the latter work without
cracking however. There is a tiny bit of shrink that can occur before
cracking will occur. When this tiny bit of shrinking occurs, if you
catch it just right, you can turn the mold over and the newly formed
piece will come free. I use a jigger and make plates, and this very
problem is an issue. The plates are formed upside down, and the first
time I made some they all cracked. I learned. Now-a-days I even use a
very tiny sharp tool to cut a releasing groove in the edge of the clay.
It helps get the releasing process started without cracking.
I try and avoid using anything with a greasy consistency on my molds.
It's anathama to an old mold maker like me. I know a lot of people use
pam and WD 40, but I don't. Then again, I don't have any molds that have
shape or pattern that makes it necesary.
Regards,
John Rodgers
Chelsea, AL
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