Greg Skipper on tue 2 dec 97
I've been sculpting reliefs and someone showed me how to make plaster
casts. They suggested that I could efficiently replicate my work and
that the copies would be as good as the originals. The one I did with
initially my "teacher" used dental floss to suspend the dried clay
relief face down into the plaster. The result was not very impressive.
To remove the original we had to use a hose with water and the original
was destroyed (which I'd spent many hours making - ugh). I have done a
couple of these and I tried putting the relief face up at the bottom and
poured plaster on top. This was better, with less air bubbles, but
still was not great. I'm using dental lab plaster.
Any help I could get would be appreciated:
1. Is there any way to not loose the original when making a cast?
(Putting WD40 on it or something? Letting it dry more before removing
it from the cast?)
2. Is there a better way to treat the cast before pressing clay into it
so that the finished product comes out with less distortion? I end up
spending a fair amount of time "finishing" the final version because
it's not perfect.
3. Any more ideas on what I might could do better?
Thanks
Greg
clay&maxwell on wed 3 dec 97
This is how I learned to make plaster molds:
- we used potters plaster (#1)
- in terms of the relief you must make certain there are no under-cuts that
would prevent the clay from releasing from the plaster
- we cast when the clay was still damp
- we placed the clay piece on a board and built a dam around it with scrap
clay (ie. a circle of clay to contain the plaster) - the board area that
was to receive the plaster was lubricated with vasoline
- the first layer of plaster was kind of splashed onto the piece by
flicking with the hand so that the plaster got into all the little
depressions etc. (a creamy thickness)
- immediatly afterwards a larger batch of plaster was mixed up to sour
cream consistency and gently "slathered" on by hand until about an inch
deep (for strength)
- after the plaster has set you should be able to remove the clay with
little difficulty
- when you use it as a mold, press the clay in to the desired thickness and
wait for it to stiffen so that it will still come out easily but not
distort - if you have trouble getting a "grip" on the clay to remove it
try using a small wad of clay (or 2) and stick it on to the cast piece -
this should help by forming a handle of sorts so you can remove the piece
- of course if you are casting a large piece just gently turning it over
and patting the plaster should be enough to release the clay and enable you
to lift the plaster off
before you try again why not make a test piece to see how it all comes
together?
good luck
deb clay in sunny Calgary
At 10:22 AM 12/2/97 EST, you wrote:
>----------------------------Original message----------------------------
>I've been sculpting reliefs and someone showed me how to make plaster
>casts. They suggested that I could efficiently replicate my work and
>that the copies would be as good as the originals. The one I did with
>initially my "teacher" used dental floss to suspend the dried clay
>relief face down into the plaster. The result was not very impressive.
>To remove the original we had to use a hose with water and the original
>was destroyed (which I'd spent many hours making - ugh). I have done a
>couple of these and I tried putting the relief face up at the bottom and
>poured plaster on top. This was better, with less air bubbles, but
>still was not great. I'm using dental lab plaster.
>Any help I could get would be appreciated:
>1. Is there any way to not loose the original when making a cast?
>(Putting WD40 on it or something? Letting it dry more before removing
>it from the cast?)
>2. Is there a better way to treat the cast before pressing clay into it
>so that the finished product comes out with less distortion? I end up
>spending a fair amount of time "finishing" the final version because
>it's not perfect.
>3. Any more ideas on what I might could do better?
>Thanks
>Greg
>
>
Ric Swenson on wed 3 dec 97
I remembered a thead earlier on CLAYART about MOLDMAKING....you might look
in the archives of CLAYART...or seek out the book at the library or
Inter-Library-Loan and take advantage of 30 + years of Don Frith's
experience making molds for ceramics. Whether you are making face molds or
pottery shapes, the basics are the same.
Author Donald E. Frith - "Mold Making For Ceramics"
ISBN 0801973597 Chilton Book Co. 227 pages . Published June 1, 1985
( bookstores will show it as "out of stock" Inter-Library Loan is your
best bet....or a good used book shop in a major city...)
re: Don Frith...
"He taught for many years at the University of Illinois in
Champaign-Urbana. He is still one of my favorite potters and the
several pieces of his that I own are among my treasures. He is retired
from teaching and living in California, making wonderful pots at the
moment, which you can see at Del Mano Gallery in L.A. Don is a super
guy, a fine teacher and a consumate craftsman."
exerpted from a post by : Harvey Sadow
HTH
Ric
>----------------------------Original message----------------------------
>I've been sculpting reliefs and someone showed me how to make plaster
>casts. They suggested that I could efficiently replicate my work and
>that the copies would be as good as the originals. The one I did with
>initially my "teacher" used dental floss to suspend the dried clay
>relief face down into the plaster. The result was not very impressive.
>To remove the original we had to use a hose with water and the original
>was destroyed (which I'd spent many hours making - ugh). I have done a
>couple of these and I tried putting the relief face up at the bottom and
>poured plaster on top. This was better, with less air bubbles, but
>still was not great. I'm using dental lab plaster.
>Any help I could get would be appreciated:
>1. Is there any way to not loose the original when making a cast?
>(Putting WD40 on it or something? Letting it dry more before removing
>it from the cast?)
>2. Is there a better way to treat the cast before pressing clay into it
>so that the finished product comes out with less distortion? I end up
>spending a fair amount of time "finishing" the final version because
>it's not perfect.
>3. Any more ideas on what I might could do better?
>Thanks
>Greg
the Gallagher's on wed 3 dec 97
Greg,
Making casts from plaster molds is a picky process, but not impossible.
Pressing the original into the wet plaster is NOT the best way to get a good
impression, as you found out.
Pouring the plaster is better, but first you want to prepare your surface for
release.
If you want to make the mold in plaster, and your sculpted original is water
base clay, you might want a mold release agent, but it's not necessary. I
have used Pam, the spray on cooking grease. Vasoline is also used, but I have
found that if you aren't careful, you can alter your piece, or leave gobs of
vasoline that will change your impression. The spray is quick and easy and
should be rather thin.
Next you want to make sure that your sculpture has no undercuts, that no part
of the sculpture sticks out so that when you pull off the mold it takes the
clay along with it.
Applying the plaster onto the original should be done carefully to avoid
trapping air, a soft paint brush is helpful. Start with a small amount, then
pour the rest slowly so as not to produce any air bubbles.
Now, if you don't need to save the original, there would be no need for the
release agent, also the release agent will sort of trash the piece anyway with
a coat of slimy grease!
As the plaster pulls the moisture from the clay, your piece will shrink,
allowing it to pull away from the sides of the mold and it should pop out
fairly clean and perfect. Length of time to wait for this will vary on the
thickness of your piece.
DO NOT wait for the piece to dry past leather hard, or you will have to chip
and scrape it out! Once the clay is free from the mold you can wash away any
remaining clay with water.
This process is used for making relief tiles and Frank Giorgini's book
explains the entire process.
Good luck. Feel free to e-mail me if you have any further questions.
Michelle, in Oregon
Puppets@msn.com
Robert Santerre on wed 3 dec 97
Greg,
We have used an automotive product called Armour-all (a leather/vinyl =
cleaner)
to achieve easy release of No.1 potter's plaster molds from plastic forms =
like a
bowl form. Did you fire the original clay sculpture before trying to make =
the
cast? Actually I'm not sure I've addressed your question. It sounds like
you're trying to release impressed clay from a plaster form/mold. Your =
problem
may the type of plaster you're using. A =231 potter's plaster mold (when
thoroughly dry) will suck water out of the impressed clay and depending on =
how
thick the impressed clay layer is it will shrink away from the mold cleanly.
For example if the clay is about 1/4 inch thick it would probably release =
from
the mold in 30 mins to 2 hrs (the amount of water in the clay will determine
actual release time). See comments below.
----------
From: Greg Skipper=5BSMTP:skipper=40aracnet.com=5D
Sent: Tuesday, December 02, 1997 9:22 AM
To: Multiple recipients of list CLAYART
Subject: Cast Questions?
----------------------------Original message----------------------------
I've been sculpting reliefs and someone showed me how to make plaster
casts. They suggested that I could efficiently replicate my work and
that the copies would be as good as the originals. The one I did with
initially my =22teacher=22 used dental floss to suspend the dried clay
relief face down into the plaster. The result was not very impressive.
To remove the original we had to use a hose with water and the original
was destroyed (which I'd spent many hours making - ugh). I have done a
couple of these and I tried putting the relief face up at the bottom and
poured plaster on top. This was better, with less air bubbles, but
still was not great. I'm using dental lab plaster.
Any help I could get would be appreciated:
1. Is there any way to not loose the original when making a cast? Fire the
original first, then spray it liberally , maybe several times with =
Armour-all
(and maybe coat first with a wax resist).
(Putting WD40 on it or something? Letting it dry more before removing =
Won't
help. The water from the plaster will degrade the raw clay sculpture. You =
need
to fire the sculpture first.
it from the cast?)
2. Is there a better way to treat the cast before pressing clay into it I
think your cast made with dental plaster is the problem. Too hard, not =
enough
water adsorption. Switch to =231 plaster. Wait for the clay to dry and =
release.
Might take a day if the clay is really wet.
so that the finished product comes out with less distortion? I end up
spending a fair amount of time =22finishing=22 the final version because
it's not perfect.
3. Any more ideas on what I might could do better?
Thanks
Greg
james klueg on thu 4 dec 97
I've used liquid hand soap as a mold release agent for years -- works
great and , since it's water soluble, it washes out entirely. Just paint
on two coats, letting each dry.
Jim Klueg
in Duluth, where it's amazingly mild (for Duluth)
Robert S. Bruch on thu 4 dec 97
If you want tio release the original and save it, you may
have to make a mold with more than two parts.
--
Bob Bruch rsb8@po.cwru.edu
Pearl Joseph on thu 4 dec 97
Dear Greg;
For one thing, fire your relief before you make a cast of it so it is solid.
Coat it with a liquid soap - (Murphy's oil soap works for me) so that it is
easily removable. If you are not sucessful you can try again without losing
the piece. Also make sure you don't have undercuts or you won't be able to
remove the piece, or to use the mold that you'v made from it. Undercuts also
tend to collect air bubbles. Watch the way you pour the plaster; that can
also produce air bubbles.
Hope this helps.
Pearl in White Plains, NY
| |
|
