John Rodgers on tue 14 dec 04
Kate,
Regards mold making with plaster .... if the model you are using to pour
plaster over has too much soap, the soap will kill the plaster and it
will be powdery. This can ruin a plaste mold.
Regards process .... If you use wet clay for your model over which to
pour plaster, you do not need to use anything as a mold release. If the
clay is wet, when the plaster sets, the clay can be peeled right out.
Then you simply trim the plaster mold with a knife, wash it with water
and set aside to dry.
I sometimes use metal mixing bowls as forms upon which to make bowls. I
also use them as slump molds in which to make bowls. Whether useing the
outside surface or the inside surface of the metal bowl, I always spray
it with WD 40. Then I lay a slab over it or in it and work it down
against the oiled surface with a sponge. If I make the clay bowl on the
inside of the metal bowl, I don't worry about shrinking, but if I drape
it over the outside, then I have to watch it carefully to remove it
before it dries enough to start cracking.
There are two ways to use a plaster mold.
One, you can lay clay directly against the plaster. If the mold is
completely dry the plaster will pull the moisture and the piece will
shrink and dry rather quickly.
Two, you can seize the surface of the mold. To seize or seal the plaster
surface, mix Tincture of green soap with water - 50/50 ratio, the with a
big sponge, dip in the soap and rub on the surface of the plaster.
Lather up good. Allow to dry a bit, then brush it smooth with a china
bristle brush Do this application three times. After the last time,
drop three drops on the soaped surface. The drops should bead up like
water on wax. If this is the case, the surface is ready to work. If you
are going to make a mold on this soaped piece, don't put more than three
layers of soap, brushed smooth and dry in between application. Spritz
the surface with alcohol to break the surface tension of the plaster as
it is poured. After setting, but while the plaster is still warm,
separate the new mold from the plaster model. It is easier to remove at
that time, as the soap is soft, and some water of hydration will help
release the soap. If stuck, dunking in hot water helps.
I much prefer using the plaster moldswith no seizing on the surface of
the plaster. Just plain old plaster surface.
Regards,
John Rodgers
Chelsea, AL
Kate Johnson wrote:
> Hi, all--
>
> the other day I asked if Armor-all might be used as a release agent--I
> use
> it when working with polymer clay, when someone (sorry, I couldn't
> find who
> in my archives!) had suggested WD 40. Thought I'd try it and find out,
> using a china bowl I've used as a mold before.
>
> Hm. It really wasn't very satisfactory--there was still that tendency of
> surface tension of wet-to-wet. I ran a pin tool under the edge to help
> release, but either my timing was off or Armor-all and a slick china mold
> aren't a good match. Just thought I'd report in with my experience...
>
> Then--my question (you KNEW there would be one!) Last week I finally
> got a
> couple of plaster molds made at class, making shapes of scrap clay, then
> pouring the plaster over them to make press molds for my redware. We
> coated
> the board and the clay with soap, to facilitate release--the soap may
> have
> been thicker than it needed to be, though. I'm thinking you need about
> dishwashing thickness and this was the hand-washing dispenser type--like
> lotion. The molds look really good--EXCEPT.
>
> There was still a bit of moist powderyness right at the edge of the mold
> after it set (don't know how else to describe it--it just didn't set
> up hard
> in a couple of places), and I'm concerned about flakes of gypsum
> getting in
> my clay. It pretty much stayed powdery enough to rub off with a
> finger, in
> those two places. I've been told you trim the clay edge with a wooden
> tool
> rather than a pin tool to avoid scratching it and getting plaster into
> the
> clay, but even the wooden tool released white bits into my edge where
> it was
> still grainy (after almost a week.)
>
> Did the plaster not get mixed well enough, was there too much soap on the
> board and it got mixed in with the plaster, and most importantly, is
> there
> anything to do to save the mold? It turned out very nice, except for
> that.
> Any way to seal it?
>
> I'm trimming the platter that's in it now below the edge, and since
> it's red
> earthenware it's easy to see the white specs and remove them, but this is
> NOT how that's supposed to work.
>
> Thanks again, in advance, patient folk...
>
> Regards,
> Kate Johnson
> Graphics/Fine Arts
> http://www.cathyjohnson.info/
> http://www.epsi.net/graphic/
> http://www.ebsqart.com/Artists/cmd_1494_profile.htm
>
> ______________________________________________________________________________
>
> 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.
>
>
Carol on tue 14 dec 04
Hi Kate,
Sorry for your plaster disaster! I learned mold-making from a great
instructor who had worked for Kohler, making... molds. Of course I
still have the occasional mess, but I learned from a pro
It sounds like there was a lump of unmixed plaster that ended up on the
edge of the mold. You didn't say anything about mixing the plaster,
but it's important to "sieve" it slowly into the water so that it
doesn't clump. I usually let it sift through my fingers as I slowly
move my hand over the container of water. Then let it slake for 3 or 4
minutes and mix it by hand - checking for & squishing any lumps - until
it thickens. It's best to keep your hand submerged in the plaster so
that you don't mix air into it... When the plaster starts to thicken,
thump the container on the outside to get any trapped air bubbles to
come to the top.
The release I like best is Murphy's Oil Soap (no connection). Apply it
sparingly with a sponge and then wipe it off. Do that a couple more
times - the object will be thoroughly covered but without leaving a
thick coat that could leave texture in the mold! I've tried Pam -
sometimes it bubbles on contact and can leave dimples in the plaster...
If it wouldn't damage the mold, you could try to trim the your mold,
removing the powdery area... Or if it's a small enough area, I
suppose you could seal it with varnish - but that will keep your mold
from absorbing water from the clay, so you want to do it very
sparingly.
Hope this helps. And... remember, when making large molds, wear short
sleeves! Good luck!
Carol Ross
On Dec 14, 2004, at 8:27 PM, Kate Johnson wrote:
Hi, all--
the other day I asked if Armor-all might be used as a release agent--I
use
it when working with polymer clay, when someone (sorry, I couldn't find
who
in my archives!) had suggested WD 40. Thought I'd try it and find out,
using a china bowl I've used as a mold before.
Hm. It really wasn't very satisfactory--there was still that tendency
of
surface tension of wet-to-wet. I ran a pin tool under the edge to help
release, but either my timing was off or Armor-all and a slick china
mold
aren't a good match. Just thought I'd report in with my
experience...
Then--my question (you KNEW there would be one!) Last week I finally
got a
couple of plaster molds made at class, making shapes of scrap clay, then
pouring the plaster over them to make press molds for my redware. We
coated
the board and the clay with soap, to facilitate release--the soap may
have
been thicker than it needed to be, though. I'm thinking you need about
dishwashing thickness and this was the hand-washing dispenser type--like
lotion. The molds look really good--EXCEPT.
There was still a bit of moist powderyness right at the edge of the mold
after it set (don't know how else to describe it--it just didn't set up
hard
in a couple of places), and I'm concerned about flakes of gypsum
getting in
my clay. It pretty much stayed powdery enough to rub off with a
finger, in
those two places. I've been told you trim the clay edge with a wooden
tool
rather than a pin tool to avoid scratching it and getting plaster into
the
clay, but even the wooden tool released white bits into my edge where
it was
still grainy (after almost a week.)
Did the plaster not get mixed well enough, was there too much soap on
the
board and it got mixed in with the plaster, and most importantly, is
there
anything to do to save the mold? It turned out very nice, except for
that.
Any way to seal it?
I'm trimming the platter that's in it now below the edge, and since
it's red
earthenware it's easy to see the white specs and remove them, but this
is
NOT how that's supposed to work.
Thanks again, in advance, patient folk...
Regards,
Kate Johnson
Graphics/Fine Arts
http://www.cathyjohnson.info/
http://www.epsi.net/graphic/
http://www.ebsqart.com/Artists/cmd_1494_profile.htm
________________________________________________________________________
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You may look at the archives for the list or change your subscription
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Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
Kate Johnson on tue 14 dec 04
Hi, all--
the other day I asked if Armor-all might be used as a release agent--I use
it when working with polymer clay, when someone (sorry, I couldn't find who
in my archives!) had suggested WD 40. Thought I'd try it and find out,
using a china bowl I've used as a mold before.
Hm. It really wasn't very satisfactory--there was still that tendency of
surface tension of wet-to-wet. I ran a pin tool under the edge to help
release, but either my timing was off or Armor-all and a slick china mold
aren't a good match. Just thought I'd report in with my experience...
Then--my question (you KNEW there would be one!) Last week I finally got a
couple of plaster molds made at class, making shapes of scrap clay, then
pouring the plaster over them to make press molds for my redware. We coated
the board and the clay with soap, to facilitate release--the soap may have
been thicker than it needed to be, though. I'm thinking you need about
dishwashing thickness and this was the hand-washing dispenser type--like
lotion. The molds look really good--EXCEPT.
There was still a bit of moist powderyness right at the edge of the mold
after it set (don't know how else to describe it--it just didn't set up hard
in a couple of places), and I'm concerned about flakes of gypsum getting in
my clay. It pretty much stayed powdery enough to rub off with a finger, in
those two places. I've been told you trim the clay edge with a wooden tool
rather than a pin tool to avoid scratching it and getting plaster into the
clay, but even the wooden tool released white bits into my edge where it was
still grainy (after almost a week.)
Did the plaster not get mixed well enough, was there too much soap on the
board and it got mixed in with the plaster, and most importantly, is there
anything to do to save the mold? It turned out very nice, except for that.
Any way to seal it?
I'm trimming the platter that's in it now below the edge, and since it's red
earthenware it's easy to see the white specs and remove them, but this is
NOT how that's supposed to work.
Thanks again, in advance, patient folk...
Regards,
Kate Johnson
Graphics/Fine Arts
http://www.cathyjohnson.info/
http://www.epsi.net/graphic/
http://www.ebsqart.com/Artists/cmd_1494_profile.htm
Kathy Forer on wed 15 dec 04
On Dec 14, 2004, at 9:27 PM, Kate Johnson wrote:
> We coated
> the board and the clay with soap, to facilitate release--the soap may
> have
> been thicker than it needed to be, though. I'm thinking you need about
> dishwashing thickness and this was the hand-washing dispenser
> type--like
> lotion.
Hi Ann,
A good parting agent will add very little in between a mold and model.
Green soap or mold lotion are best when well lathered into a plaster
surface, allowed to dry and then rinsed off. It's necessary to repeat
the process several times until water beads up on the surface and it
looks shiny and feels smooth. The resulting mold will have barely any
disturbance of texture as it would with a thick or messy parting agent.
Because Tincture of Green Soap contains alcohol and green soap is soft
and more alkaline (7-8.5ph) than a hard soap like castile soap, it will
both lather and leave little residue. You can even use a fine brush
(very soft toothbrush even) under running water to remove any lingering
residue and if it still beads up well, the mold is okay. It also smells
nice.
But TGS can be hard to find locally at the moment you need it
( has a
good price). The biggest problem with dish soap or hand-washing lotion
may be that they're either too hard or too fat or won't lather enough
to really get into and seal the plaster pores, leaving dry residue that
will mix with plaster, exactly what you experienced in the cheesy edges
which can extend deeper under the surface. It would probably be best to
redo the mold or carve into it until you eliminate the soft spots. You
could try sealing it with shellac and then adding a serious parting
agent but you'll lose your surface.
Commercial mold lotion is quite easy to use and effective, and not as
process intensive as green soap.
Kathy
Bob Masta on wed 15 dec 04
Kate:
I've found that hand-washing dispenser-type "soaps" are
not soaps at all, they are detergents. I've had the same
powder problems with them, and have read that release
agents should use real soap. I have since used Ivory
soap flakes with good results, although it's a hassle to
mix it up. (I had a very old box in the laundry room;
don't know if the current product is still real soap.)
Best regards,
Bob Masta
potsATdaqartaDOTcom
Snail Scott on wed 15 dec 04
At 08:27 PM 12/14/2004 -0600, you wrote:
>Last week I finally got a
>couple of plaster molds made at class, making shapes of scrap clay, then
>pouring the plaster over them to make press molds for my redware. We coated
>the board and the clay with soap, to facilitate release--the soap may have
>been thicker than it needed to be, though. I'm thinking you need about
>dishwashing thickness and this was the hand-washing dispenser type--like
>lotion...
Clay will release from plaster with no release agent at
all. To release plaster from plaster, any soap will do.
(NOT detergent; actual soap - detergents are different,
and most dishwashing 'soaps' are detergents.) I like
Murphy Oil Soap, as do many mold-makers. There are
specialty mold soaps, but Murphy's does a good job,
and it's cheap and easy to find. (It's available in
the cleaning-products aisle of most stores that sell
such things, including supermarkets and Wal-Mart.)
There should be NO visible thickness to the soap layer
after application. Brush it on, let it soak in, repeat,
then wipe off any excess and buff smooth. You shouldn't
need any release at all for the clay pattern, though.
>
>There was still a bit of moist powderyness right at the edge of the mold
>after it set (don't know how else to describe it--it just didn't set up hard
>in a couple of places), and I'm concerned about flakes of gypsum getting in
>my clay. It pretty much stayed powdery enough to rub off with a finger, in
>those two places. I've been told you trim the clay edge with a wooden tool
>rather than a pin tool to avoid scratching it and getting plaster into the
>clay, but even the wooden tool released white bits into my edge where it was
>still grainy (after almost a week.)
Do you mean the parting line - the edge next to the
art? It may very likely be the result of excess mold
soap. Slight powdery residues of plaster won't matter
much for stoneware, as it tends to melt into the mix,
but with earthenware, it may still show. You won't
get the dreaded 'lime pop', though, since it's all on
the surface, and small particles anyway. If it's just
a slight dusting of residue, try glazing over it on
a test sample - it might be OK.
Quite right to use plastic or wood against the mold -
no scratchy metal tools. That won't help much with this
situation, though. Scrape back the bad areas of plaster
and plan on doing more cleanup on the things you make,
or make a new mold.
If it's a one-part mold made against a tabletop, for
stance, just soap the tabletop before placing the clay
pattern down, and apply plaster. No need for a release
agent on the clay itself. Make sure the plaster gets
well down against the crevices - use a brush to sweep
out any trapped air bubbles where the clay meets the
table. If any plaster gets under, it's easily trimmed
away afterward, but you really want a good solid edge
(as you've discovered!).
-Snail
John Rodgers on wed 15 dec 04
Kate,
I probably should have gone just a bit more in depth about process.
When working with plaster and creating a model from plaster, the
application of a mold soap to the plaster surface creates a
waterproof/repellant surface. Soap is a stearate compound, and the
stearate radical conbines chemically with the calcium in the plaster to
produce calcium stearate, which is water impervious. When you work the
surface of the plaster over with a sponge and the soap a very thin layer
of calcium stearate is formed right on the surface only molecules
thicke, but it is enough. usually the first coat of soap is enough to
create the layer. This seals or "seizes" the surface to prevent any
further penetration by water or other soap. However, by applying the
soap three times, and brushing dry in between each layer, you ensure
thatere are no holes in the stearate layer, and you acutally build up a
very thin layer of very soft soap. This very soft soap will soften even
more once plaster is poured over it, due both to heat of hydration, and
the water present in the newly poured plaster, making for easy
separation, especially if separation is done before the newly formed
mold cools after setting.
There are numerous commercial mold soaps available - English Crown is
one. But I prefer to use Tincture of Green Soap which is available in
most drug stores in small bottles ( I buy it by the gallon from the drug
supply houses) and I also like Murphy's Oil Soap. My first choice is
however the Tincture of Green Soap. In any case with soaps however, they
need to be cut 50/50 with water before application.
I make so many molds that I keep a series of art painters 4 inche china
bristle brushes on hand for brushing the drying surfaces of the mold.
This helps to polish the soap surface to get a smoother finish and
remove excess moisture. If there is a shine on the surface of a mold, it
should be brushed until dull. he shine is an indication that the surface
is still wet, and that you do not want when you cast the plaster. Wet
soap will mix into the wet plaster and kill the set of the plaster and
you end up with powder on setting. This may be what happened to your
first efforts where you got powder after the mold set.
Also, TO MUCH soap- even dry - will cause "alligator hide" in the
surface of the plaster cast. This is a condition of roughness that makes
the mold useless.
Good luck on your project.
Regards,
John Rodgers
Chelsea, AL
Kate Johnson wrote:
> Hi, all--
>
> the other day I asked if Armor-all might be used as a release agent--I
> use
> it when working with polymer clay, when someone (sorry, I couldn't
> find who
> in my archives!) had suggested WD 40. Thought I'd try it and find out,
> using a china bowl I've used as a mold before.
>
> Hm. It really wasn't very satisfactory--there was still that tendency of
> surface tension of wet-to-wet. I ran a pin tool under the edge to help
> release, but either my timing was off or Armor-all and a slick china mold
> aren't a good match. Just thought I'd report in with my experience...
>
> Then--my question (you KNEW there would be one!) Last week I finally
> got a
> couple of plaster molds made at class, making shapes of scrap clay, then
> pouring the plaster over them to make press molds for my redware. We
> coated
> the board and the clay with soap, to facilitate release--the soap may
> have
> been thicker than it needed to be, though. I'm thinking you need about
> dishwashing thickness and this was the hand-washing dispenser type--like
> lotion. The molds look really good--EXCEPT.
>
> There was still a bit of moist powderyness right at the edge of the mold
> after it set (don't know how else to describe it--it just didn't set
> up hard
> in a couple of places), and I'm concerned about flakes of gypsum
> getting in
> my clay. It pretty much stayed powdery enough to rub off with a
> finger, in
> those two places. I've been told you trim the clay edge with a wooden
> tool
> rather than a pin tool to avoid scratching it and getting plaster into
> the
> clay, but even the wooden tool released white bits into my edge where
> it was
> still grainy (after almost a week.)
>
> Did the plaster not get mixed well enough, was there too much soap on the
> board and it got mixed in with the plaster, and most importantly, is
> there
> anything to do to save the mold? It turned out very nice, except for
> that.
> Any way to seal it?
>
> I'm trimming the platter that's in it now below the edge, and since
> it's red
> earthenware it's easy to see the white specs and remove them, but this is
> NOT how that's supposed to work.
>
> Thanks again, in advance, patient folk...
>
> Regards,
> Kate Johnson
> Graphics/Fine Arts
> http://www.cathyjohnson.info/
> http://www.epsi.net/graphic/
> http://www.ebsqart.com/Artists/cmd_1494_profile.htm
>
> ______________________________________________________________________________
>
> 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.
>
>
Kate Johnson on wed 15 dec 04
Hi Snail, Carol, John, Kathy, those who answered offlist, and all-
Sorry to be slow responding, my email has been a nightmare
lately...difficult to stay online, sometimes I can send and not
receive...ack! I do truly appreciate all your help! Snail's just came
through so I'm answering quickly before I'm exiled to cyberspace again.
>
> Clay will release from plaster with no release agent at
> all.
Yep, it wasn't the clay part I was worried about. I made a platter shape,
upside down, on a wooden board. I was afraid it wouldn't release from the
board...
To release plaster from plaster, any soap will do.
> (NOT detergent; actual soap - detergents are different,
> and most dishwashing 'soaps' are detergents.) I like
> Murphy Oil Soap, as do many mold-makers.
Nuts, I actually have some of that, and just ordered the green soap. Oh
well.
There are
> specialty mold soaps, but Murphy's does a good job,
> and it's cheap and easy to find. (It's available in
> the cleaning-products aisle of most stores that sell
> such things, including supermarkets and Wal-Mart.)
> There should be NO visible thickness to the soap layer
> after application. Brush it on, let it soak in, repeat,
> then wipe off any excess and buff smooth.
That was, I'm sure, part of the problem. We were in our usual in-class
hurry, and just slathered on one thickish layer of liquidy hand
soap/detergent from the dispenser.
You shouldn't
> need any release at all for the clay pattern, though.
Try try again...
>
>>
>>There was still a bit of moist powderyness right at the edge of the mold
>>after it set (don't know how else to describe it--it just didn't set up
>>hard
>>in a couple of places), and I'm concerned about flakes of gypsum getting
>>in
>>my clay. It pretty much stayed powdery enough to rub off with a finger,
>>in
>>those two places. I've been told you trim the clay edge with a wooden
>>tool
>>rather than a pin tool to avoid scratching it and getting plaster into the
>>clay, but even the wooden tool released white bits into my edge where it
>>was
>>still grainy (after almost a week.)
>
>
> Do you mean the parting line - the edge next to the
> art?
The very edge of what would be the platter...the upper edge, when the mold
is in use. The idea, with this type of thing, is to cut the clay off even
with the top of the mold, using the mold edge as your guide. I've read that
you want to use a wooden tool and run it along this edge (the part that was
flat to the board when making the mold) but being careful not to scratch the
mold and get gypsum in the clay. With my upper edge buggered up, I'm
trimming a bit below there, with my wooden tool. Not so even as it should
be, but oh well...
It may very likely be the result of excess mold
> soap. Slight powdery residues of plaster won't matter
> much for stoneware, as it tends to melt into the mix,
> but with earthenware, it may still show. You won't
> get the dreaded 'lime pop', though, since it's all on
> the surface, and small particles anyway.
OH GOOD! THAT was what I was worried about. Since it's redware, it
definitely DOES show, but it's reasonably easy to pick or sponge off...
If it's just
> a slight dusting of residue, try glazing over it on
> a test sample - it might be OK.
I don't glaze the backs of platters anyway, since "they" didn't. No
problem!
>
> Quite right to use plastic or wood against the mold -
> no scratchy metal tools. That won't help much with this
> situation, though. Scrape back the bad areas of plaster
> and plan on doing more cleanup on the things you make,
> or make a new mold.
I do plan to make a new one...I don't think we mixed the plaster well
enough, as I think John suggested. When my buddy makes molds, they're for
large sculptures and the edges are usually blended or hidden, so none of
this is quite as critical, for his work. The edge is the thing you see
first on a platter, and it needs to be as even as possible!
>
> If it's a one-part mold made against a tabletop, for
> stance, just soap the tabletop before placing the clay
> pattern down, and apply plaster. No need for a release
> agent on the clay itself. Make sure the plaster gets
> well down against the crevices - use a brush to sweep
> out any trapped air bubbles where the clay meets the
> table.
That would have been good, too. We weren't being as careful of edges as we
might have been.
If any plaster gets under, it's easily trimmed
> away afterward, but you really want a good solid edge
> (as you've discovered!).
>
OH yeah.
Many thanks, all. I did clean up the mold quite a bit more, and it's usable
till I manage to make The Perfect One.
Best--
Kate
Kate Johnson on wed 15 dec 04
Hi Bob...
>
> I've found that hand-washing dispenser-type "soaps" are
> not soaps at all, they are detergents. I've had the same
> powder problems with them, and have read that release
> agents should use real soap. I have since used Ivory
> soap flakes with good results, although it's a hassle to
> mix it up. (I had a very old box in the laundry room;
> don't know if the current product is still real soap.)
No, it isn't, alas. I had a stash for a long time, myself! I've ordered
some tincture of green soap from my pharmacist, ought to last for a while.
I keep shredded up hard soap soaking in water, that makes real soap
liquid...if I'd been home, I could have used that!
I trimmed the mold and got rid of most of that, so hopefully it will work
all right--till I can do a better job on the next try!
Thanks to all who have made suggestions, I'm learning....
Best--
Kate
Kate Johnson on thu 16 dec 04
Hi John! >
> however the Tincture of Green Soap. In any case with soaps however, they
> need to be cut 50/50 with water before application.
Whoa, now THERE is something I'm glad I noticed. I hadn't seen that
anywhere else, even in the two books I have that cover mold making. THANK
YOU.
> I make so many molds that I keep a series of art painters 4 inche china
> bristle brushes on hand for brushing the drying surfaces of the mold.
> This helps to polish the soap surface to get a smoother finish and
> remove excess moisture. If there is a shine on the surface of a mold, it
> should be brushed until dull. he shine is an indication that the surface
> is still wet, and that you do not want when you cast the plaster. Wet
> soap will mix into the wet plaster and kill the set of the plaster and
> you end up with powder on setting. This may be what happened to your
> first efforts where you got powder after the mold set.
I'm SURE it was. We used thick soap/detergent and didn't allow it to dry,
at ALL. Siiiigh...live and learn, eh?
>
> Also, TO MUCH soap- even dry - will cause "alligator hide" in the
> surface of the plaster cast. This is a condition of roughness that makes
> the mold useless.
That part might not be a problem with what I'm doing at present, though I
can certainly see how it might if you were making a mold of a complex form.
I just need simple press molds for 18c style platters and bowls, and usually
utilize the canvas-textured surface as the back of the item, so it's already
rough, purposely.
>
> Good luck on your project.
Thank you, and for all your wonderful advice. I have several folders under
my basic pottery one...one is called Answers, and your post is going right
there, along with the others that addressed this problem.
Best--
Kate
Ama Menec on sat 18 dec 04
Hi Kate,
I've not used soap myself as I've never needed to cast plaster onto plaster,
so to release from, say, a wood board that the original clay item is sitting
on, I use Vaseline diluted with white spirit. I mix white spirit and
Vaseline until they are runny and pretty thin, and paint it on thinly onto
the wood only part. Any surplus white spirit evaporates in the time it takes
to make up the plaster to be poured, and if I notice just before pouring
that the wood area is very matt, I may quickly paint on another THIN coat
just before I pour. It doesn't leave a texture if it's on good and thin.
I trim the edges of my moulds using an old plastic credit card/phone
card/junk mail credit card sized bit of plastic. Gets them all nice and
level and doesn't wreck your mould.
Good luck with the next one.
Ama, Totnes, Devon, UK.
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