Donald G. Goldsobel on tue 15 mar 05
Canvas can be placed on top of the clay and stapled to the frame. It is a
great wedging surface and you NEVER get chunks or specks of plaster in the
clay.
Donald
----- Original Message -----
From: "Mark Dal Pra"
To:
Sent: Tuesday, March 15, 2005 5:24 AM
Subject: rework plaster question
>
Mark Dal Pra on tue 15 mar 05
Hello,
I am currently working at an art center. They have two good plaster drying tables.
We have one that the plaster seems to flake off of when drying clay on it. Is there
something I can do to make it harder or Where can I learn about make up a plaster
drying table that won't flake off into the clay. Thanks so much I really appreciate all
that I have learned from this listserve.
Thanks again
Mark D.
Craig Clark on tue 15 mar 05
Mark, if you are having flacking problems with the plaster then you
might try and cover it with light weight canvas that you can easily
remove after the clay has set. The removal of the canvas will allow the
plaster to dry out more quickly after each use.
How large are the drying forms? If you are not dead set on keeping
the existing plaster form then go ahead and just break out the old
plaster and cast up another one. It is easy to do, plaster is
inexpensive and you can use a hydrocal, which is harder than the number
one potter plaster for a stronger surface. The disadvantage to the use
of hydocal, or stone for that matter, versus a number one pottery
plaster is that they do not absorb water as readily as the softer plaster.
A third option would be to try and mix up a small amount of plaster
and "fill" the areas of distress though this route will most likely have
the least favorable results. You may have some real bonding issues with
the new plaster onto the old.
Hope this helps
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
Jeff Longtin on wed 16 mar 05
Hey Mark,
It's likely the best option is to pour a new plaster drying surface. It
sounds like your plaster has seen a few years and it unlikely you can patch it.
The flaking is the result of moisture passing from the clay into the plaster.
This moisture carries minerals with it and these minerals deteriorate the
plaster.
As the plaster itself dries the moisture contained within moves to the
surface, and with it, the minerals. Thus people sometimes find it helpful to remove
this mineral saturated layer of plaster. Typically, however, this is more
often done with slip cast molds. With plaster wedging tables it might be best just
to remake the table surface.
Also, it might be best to prop the plaster surface in some way so that the
trapped moisture moves through the slab. If the plaster slab sits on a non
porous surface the moisture will come out the same way it went in and thus your
surface will become saturated with minerals, and thus flake, yet again. If the
slab is propped, ventilated, the moisture will move through the slab and the
clay surface will remain durable longer.
take care
Jeff Longtin
Roger Korn on wed 16 mar 05
The problem may be insufficient support for the table, allowing it to
flex slightly in use. This will cause the upper surface to be in
compressive shear, causing spalling of the surface plaster. A solution
may be to make the table more rigid by adding bracing, then to remove
the failing surface by sanding and scraping. Do the work outside, wear a
mask, and prevent any of the plaster from getting into any clay, where
it could result in future "lime pops".
Just a thought,
Roger
You wrote:
I am currently working at an art center. They have two good plaster drying tables.
We have one that the plaster seems to flake off of when drying clay on it. Is there
something I can do to make it harder or Where can I learn about make up a plaster
drying table that won't flake off into the clay.
--
McKay Creek Ceramics
In OR: PO Box 436
North Plains, OR 97133
503-647-5464
In AZ: PO Box 463
Rimrock, AZ 86335
928-567-5699
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