Val on wed 17 nov 99
Andrea wrote:....
I have tried making several molds for slipcasting and am having great
diffuculties with removing the cast piece. It is a 3 part mold that is
poured from the base of the tub. The problems I am having are that as
the piece shrinks on the hump side of the mold it cracks in half. I
would take it off the mold earlier if I could but it won't release.The
mold as angled walls and no undercuts. Any ideas??? I'm tearing my
hair out!!Thanks Andrea
I know there is a product that sprays on the mold before you fill it
....it is called mold release....also some people use baby powder
inside....don't know if this will work for you.....good luck
Val Mann w.w.
val@tlaz.com
Production Micrographics, Tweedsmuir Histories,& Newspaper dupes available.
London Ont. Canada 35mm & l6mm microfilming, supplies
Yesterday's Child Ceramics, bisque available
www.tlaz.com
icq #1592406
fax-(519) 649-1025,phone (519)649-0119
YOU'RE NEVER A LOSER UNTIL YOU QUIT TRYING!
C. Rasko on fri 19 nov 99
Be very careful about using just any product called Mold Release in a plaster
mold. It must specifically state that it is for plaster molds. Some mold
release products are for use with plastic, latex or rubber molds, not
plaster. They will seal up the pores in the plaster and make the mold
useless.
Baby powder often has moisturizing ingredients or perfume oils that can also
seal the pores in plaster. If the pores are sealed, the moisture will not be
drawn out of the slip and the sticking problem will become worse.
Human hands also have oil that is constantly being produced. It is a good
idea to keep hands off of the mold cavity to prevent oil deposits from
building up causing the greenware to stick.
Jonathan Kaplan on sat 20 nov 99
>----------------------------Original message----------------------------
>Be very careful about using just any product called Mold Release in a plaster
>mold. It must specifically state that it is for plaster molds. Some mold
>release products are for use with plastic, latex or rubber molds, not
>plaster. They will seal up the pores in the plaster and make the mold
>useless.
>
>Baby powder often has moisturizing ingredients or perfume oils that can also
>seal the pores in plaster. If the pores are sealed, the moisture will not be
>drawn out of the slip and the sticking problem will become worse.
>
>Human hands also have oil that is constantly being produced. It is a good
>idea to keep hands off of the mold cavity to prevent oil deposits from
>building up causing the greenware to stick.
Its important that we provide accurate information and not erroneous
information that is misleading.
Mold releases, also called "parting compounds" are designed to seal the
pores so that rubber, plaster, or other mold making materials can be used
to make reproductions of mold parts, or, to seal models to pull a mold or
mold parts from. There are specific "parting compounds" used for gypsum
work.
A "mold release" is called parting compound and is used to separate plaster
from plaster, rubber from plaster, plaster from rubber, etc. etc. NOT to
separate slip from plaster.
And yes, the mold needs to be permeable to allow for slip casting. Baby
powder ot talc is often used in some casting situations to allow for an
easy release of the cast clay part or in areas that may be problematic. If
the working molds are made correctly at the right plaster to water ratio,
and if the slip has been correctly formulated, there should be no problem
with casting.
The first mold, called the block mold is made directly from the model. A
few ceramic castings can be taked from the block to samples. A master mold,
also known as a case mold is then taken from the block mold. These can be
made from gypsum, rubber, or combinations. The block mold needs to be
preped with parting compound to prevent the rubber or the gypsum poured
into/around etc. it from adhering. Once the case mold is made, it too needs
to be preped with parting compound so that production molds, also known as
working molds can be made to have an efficient production.
Lets get our facts straight before we disemenate them on this list.
Jonathan
Jonathan Kaplan
Ceramic Design Group LTd/Production Services
PO Box 775112
Steamboat Springs, CO 80477
(970) 879-9139 voice and fax
http://www.sni.net/ceramicdesign
UPS: 1280 13th St. Unit13
Steamboat Springs, CO 80487
Kat Fode on sat 2 mar 02
Dave wrote:
Date: Fri, 1 Mar 2002 06:41:30 -0700
From: Dave Finkelnburg
Subject: Re: Mold release question
>Moldmakers,
> Do you use greensoap for mold release when pouring plaster to make a
>mold? If so, do you use it full strength or dilute it with water? Thanks!
> Dave Finkelnburg in still-winter Idaho
Dave
I have used a product called Murphys Oil. It is a cleaning product for
hardwood floors, etc... (it is oil based) Anyhow I have used it for
a mold release agent by mixing it with water and putting a thin layer
on the master mold. Works great!
Kat
kat@digitalfire.com
islandplace on sun 3 mar 02
Been following this thread and am confused; molds are new to me. Are we =
talking about releasing clay from mold or seperating the plaster =
sections when making molds? If the former, it would seem the sugestions =
that seal the plaster would prevent the plaster from drawing moisture =
from the clay and would take considerably longer to dry.
Mike=20
BVCuma on mon 4 mar 02
Are we talking about releasing clay from mold or seperating the plaster
sections when making molds? If the former, it would seem the sugestions that
seal the plaster would prevent the plaster from drawing moisture from the
clay and would take considerably longer to dry.
Mike
___________________________
When making moulds
one is creating a negative of
some form, in our case...clay.
There is no need to seal the plaster
from the clay as you mention.
To avoid undercuts one must make multiple pieces
of the plaster mould....more complex, more plaster sections.
If a sealing barrier is not created at the plaster to plaster connections
they will bond and break on your attempt to separate.
I find when mutiple sections require the support of a mother mould.
A coating of clay slip provides an easy simple barrier...
Just brush it on...it washes off easily.
Make sure you don't smooth the sections to nicely
or you will not getting a good positive seating
and spend too much time trying to place your sections.
Also a permanant marker is helpful...
when "cracking" open your freshly made mould
Otherwise the seperating line can be difficult to see
resulting in chips when prying open.
Something like that...
Bruce
Longtin, Jeff on mon 4 mar 02
Mike,
Couple things,
Yes Murphy's creates a sealing coat and yes that coat interferes with
absorption BUT the great thing about Murphy's is that it breaks down in
about two weeks and your plaster original is good as new.
Years ago I did a mold for a doll artist and she told me she regularly used
a rubber mold to make her pocelain pieces. ( She was press molding the clay
of course.) Though I still can't believe it would be an effective molding
technique she did swear by it.
Jeff Longtin
Complex Molds Made Easy
Minneapolis
-----Original Message-----
From: islandplace [mailto:islandplace@INETW.NET]
Sent: Sunday, March 03, 2002 7:28 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: mold release
Been following this thread and am confused; molds are new to me. Are we
talking about releasing clay from mold or seperating the plaster sections
when making molds? If the former, it would seem the sugestions that seal the
plaster would prevent the plaster from drawing moisture from the clay and
would take considerably longer to dry.
Mike
____________________________________________________________________________
__
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Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
Marie Gibbons on mon 4 mar 02
Jeff.Longtin@WESTGROUP.COM writes:
> Years ago I did a mold for a doll artist and she told me she regularly used
> a rubber mold to make her pocelain pieces. ( She was press molding the clay
> of course.) Though I still can't believe it would be an effective molding
> technique she did swear by it.
>
I have also used silicone molds with press molding clay... i work in raku c
...
it did work very well, the nice part about the silicon or rubber mold would
be that you can stretch / pull it off the clay if you have any undercuts,
that is why i did a silicone mold. I did learn that the clay was best cut to
slabs and left out in the air for a bit to dry... too wet of clay would leave
a terry cloth type of look to the piece as it was sticking to the silicone.
btw.... the piece I am talking about will be at the Kansas City Artists
Coalition, in the new works gallery (the basement) it is part of a show
entitled bodytext, some wonderful pieces in that show... I hope you will get
a chance to see it if you are going to nceca
marie gibbons
www.oooladies.com
Snail Scott on mon 4 mar 02
At 11:15 AM 3/4/02 -0600, you wrote:
>Yes Murphy's creates a sealing coat...but it breaks down...
[AND]
>...[doll artist] told me she regularly used
>a rubber mold to make her pocelain pieces....still can't believe it...
Nan Smith also does this. I had been making rubber
molds for years, to pour wax for bronze casting,
but never thought to apply the method to clay. When
I read about Nan Smith's use of rubber for press
molds, I let out a great big Homer-Simpson-style
"Doh!" It really works well. Not for slip-casting,
of course, where the mold's absorption is an essential
factor, but for press-molding it's a really useful
option.
Plaster is a heck of a lot cheaper, so I still use
it most of the time, but the flexibility of the rubber
allows for molding otherwise-difficult forms.
Also, fiber-impregnated plaster (or plaster-soaked
fiber) makes fine press-molds. The fiber intereferes
with abosrption, but as noted above, that doesn't
really matter much with press-molding. And the fiber
allows the plaster to be much thinner and lighter in
weight.
(And, I will confirm the usefulness of Murphy's Oil
Soap as a mold-making release agent for plaster slip-
casting molds. Inexpensive, available anywhere, and
as you observed it doesn't seem to have any lasting
effect on absorption.)
-Snail
>Jeff Longtin
>Complex Molds Made Easy
>Minneapolis
>
>-----Original Message-----
>From: islandplace [mailto:islandplace@INETW.NET]
>Sent: Sunday, March 03, 2002 7:28 AM
>To: CLAYART@LSV.CERAMICS.ORG
>Subject: Re: mold release
>
>
>Been following this thread and am confused; molds are new to me. Are we
>talking about releasing clay from mold or seperating the plaster sections
>when making molds? If the former, it would seem the sugestions that seal the
>plaster would prevent the plaster from drawing moisture from the clay and
>would take considerably longer to dry.
> Mike
>
>____________________________________________________________________________
>__
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at
>melpots@pclink.com.
>
>___________________________________________________________________________
___
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
>
Hendrix, Taylor J. on tue 17 sep 02
Hey all:
I have done some archive diving for mold releasing agents, and I was =
hoping to get some clarification for my particular case. I want to make =
some hump molds out of some bowls I found at (God, forgive me!) WalMart. =
Thank you Martha Stewart. I poured a 10 inch bowl using a very light =
coating of vegetable oil on the surface of the plastic bowl, but it was =
difficult to get it to release. I got it out while the plaster was =
still warm. I also tried using dishwashing soap smeared in the bowl, =
but that particular mold came out with great difficulty and the surface =
was terrible. Will Murphy's Oil Soap or shaving cream from the tube be =
effective releasing agents for plaster masters? Thanks for the help.
Taylor,
In coolish Waco STILL waiting for that Latin translation.
Pottery by Dai on wed 18 sep 02
> Now, God forgive me, but isn't Martha Stewart at K-Mart?
I think, Catherine, that it's Zeller's---at least in Canada. The plague
hasn't yet spread to WalMart.
Dai in Armstrong, BC
potterybydai@telus.net
nightfire@telus.net
www.potterybydai.com
Take your work seriously---take yourself lightly. Unknown
Dale Neese on wed 18 sep 02
I have had good results with a light coat of PAM cooking spray.
Dale Tex
Pottery by Dai on wed 18 sep 02
Hi, Taylor - try Vaseline on the bowl. That's what I usually use (even when
making a plaster form from a plaster master) and rarely have any problems.
I have a big jar of the stuff, and a piece of sponge to apply it.
For plaster-to-plaster, I drill a very small hole in the middle of the
master, which is easily covered by the Vaseline, and after the new mold sets
up, I place my compressed air nozzle right up against the hole and give it a
"squirt" to release the two pieces from each other.
Note: this method works really well when using the molds for slab work, but
not for slipcasting. The Vaseline residue would prevent the
sucking-out-the-water action necessary to firm up the walls of the slipcast
piece.
Good luck!
Dai in Armstrong, BC
potterybydai@telus.net
nightfire@telus.net
www.potterybydai.com
Take your work seriously---take yourself lightly. Unknown
Marianne Lombardo on wed 18 sep 02
I found that Murphy's Oil Soap works well.
Marianne Lombardo
Omemee, Ontario, Canada
email: mlombardo@nexicom.net
>Will Murphy's Oil Soap or shaving cream from the tube be effective
releasing agents for plaster masters?
Catherine White on wed 18 sep 02
Hey, Taylor...... I'm using several cheap plastic bowls and plates, some
very large, for molds. Bought them at good old WalMart!
I used them directly but intend making plaster molds so will await answers
to your question.
Now, God forgive me, but isn't Martha Stewart at K-Mart?
Catherine in Yuma, AZ
----- Original Message -----
From: "Hendrix, Taylor J."
To:
Sent: Tuesday, September 17, 2002 8:28 PM
Subject: Mold release
Hey all:
I have done some archive diving for mold releasing agents, and I was hoping
to get some clarification for my particular case. I want to make some hump
molds out of some bowls I found at (God, forgive me!) WalMart. Thank you
Martha Stewart. I poured a 10 inch bowl using a very light coating of
vegetable oil on the surface of the plastic bowl, but it was difficult to
get it to release. I got it out while the plaster was still warm. I also
tried using dishwashing soap smeared in the bowl, but that particular mold
came out with great difficulty and the surface was terrible. Will Murphy's
Oil Soap or shaving cream from the tube be effective releasing agents for
plaster masters? Thanks for the help.
Taylor,
In coolish Waco STILL waiting for that Latin translation.
____________________________________________________________________________
__
Send postings to clayart@lsv.ceramics.org
You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/
Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
Alistair Gillies on wed 18 sep 02
Hi,
Each of the previous replies show the correct way of keeping plaster
from keying in to a shape - however if you can put up with some small
'fold' lines [if your clay surface is going to be worked on] then you
can use cling film which gives you a guaranteed release.
Works on odd shapes and materials as well - I have made molds of limbs
using it.
All the best,
Alistair
Shropshire, England
Alistair Gillies
AGP Studio
01952 882909
07973 866198
www.agpstudio.co.uk [The builders are still working]
www.allblackedup.co.uk [English Ceilidh Band]
Ingeborg Foco on wed 18 sep 02
Try WD 40. Works great for me
Ingeborg
the Potter's Workshop & Gallery
St. James City, Florida
Snail Scott on wed 18 sep 02
At 10:28 PM 9/17/02 -0500, you wrote:
>...Will Murphy's Oil Soap or shaving cream from the tube be effective
releasing agents for plaster masters?
I have generally had good results from Murphy's
Oil Soap in similar applications.
-Snail
Alan Lent Sr. on wed 18 sep 02
Seems to me that when my mother was doing "Death Masks" or whatever they are
called, she would smear us with a liberal coating of Vaseline. As the
plaster heats during curing the Vaseline gets real thin and smooth. She
also used to stick a straw down to forehead, etc. so she could release
vacuum around face. Maybe you need a small hole through your bowl, if it is
plastic, or a small straw through your plaster to let air in to make it
release better.
Good luck!!
Alan
Jeff Longtin on wed 18 sep 02
Taylor,
Couple things are missing from your description so I'll make a few educated
guesses.
For the most part plaster will not stick to plastic so a seperator is not
necessary. In fact any substance you apply to the plastic will actually
contaminate the plaster surface, as you've already experienced. (As the
plastic is non porous any applied substance will only sit on the surface and
therefore be absorbed by the plaster.)
Not sure from your description why you are having sticking problems but I'm
guessing a greater problem is your mixing process. As you are molding a
fairly rounded form I would suggest you increase your mixing times.
Odd tidbit about mixing times and plaster: The longer you mix the plaster
before pouring the less the plaster expands in the form.
When pouring such a simple form as you describe I'll often mix the plaster
until it reaches a "melted icecream" state, i.e. my spatula will leave swirl
marks in the mix but the mix is still somewhat pourable. As you don't have
any undercuts in your form it doesn't sound like air bubbles will be such a
concern.
Generally speaking if you mix according to proscribed proportions and you mix
for a slightly longer period you should? be able to demold in about 25
minutes. If you do so you can remove the plaster form before it has a chance
to expand further and "lockup" in your form. If, however, it has locked up I
sometimes leave plaster in a form so it can shrink overnight.
(Apparently plaster is in an expanding mode while it eminates steam but once
cooled it shrinks back to its molded size.)
(Make sure to use lukewarm or tepid water.)
Good luck
Jeff Longtin
Rob House on thu 19 sep 02
On Tue, 17 Sep 2002 22:28:54 -0500, Hendrix, Taylor J.
wrote:
>Hey all:
>
>I have done some archive diving for mold releasing agents, and I was
hoping to get some clarification for my particular case. I want to make
some hump molds out of some bowls I found at (God, forgive me!) WalMart.
Thank you Martha Stewart. I poured a 10 inch bowl using a very light
coating of vegetable oil on the surface of the plastic bowl, but it was
difficult to get it to release. I got it out while the plaster was still
warm. I also tried using dishwashing soap smeared in the bowl, but that
particular mold came out with great difficulty and the surface was
terrible. Will Murphy's Oil Soap or shaving cream from the tube be
effective releasing agents for plaster masters? Thanks for the help.
>
>
>Taylor,
>In coolish Waco STILL waiting for that Latin translation.
Hey Taylor,
Murphy's Oil Soap has always worked for me...brush it on pretty cleanly
with few bubbles + allow to "dry". Vaseline will work but the surface will
probably suck. Pam kitchen spray has also proven useful, but it's not that
great. The main thing to remember is that no mold release will release a
mold that can't get out in the first place (i.e. draughtability). If the
original won't let the mold go with out either part breaking, you need to
adjust your mold to the original (parts that lock into one mold) or adjust
the original (add clay or plasticine to allow the mold to release).
Lemme know how it goes. - - - - - Rob House
____________________________________________________________________________
Lorraine Pierce on thu 19 sep 02
HI! Have you tried WD-40 as a mold release for non-plaster molds? You can
buy it by the gallon in an automotive store. Good luck. Lori Pierce in New
Port Richey, Fl.
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