ann@annbclay.com on wed 5 nov 08
I am trying to find a way to make molds of some 3d, 360 degree sculpture
parts but need them to remain workable (leather hard) after removing
from the mold. (they do not need to be hollow, but will have undercut
areas)
I've seen an artist who has flexible molds of female figures that are at
least 24" x 8" x 8" and pushes clay up into the mold including the head
and neck area. Then peels the mold off the piece and continues to
manipulate the sculpture. Does anyone know more about this type of
technique or have recommendations on other techniques I can look into?
Any books or printed materials available?
Thanks,
annb
--
www.annbclay.com
Ann Burdette Baker
331 Old Tory Trail
Aiken, SC 29801
"I am always doing things I can't do, that is how I get to do them."
--Pablo Picasso
Snail Scott on thu 6 nov 08
On Nov 5, 2008, at 4:37 PM, ann@annbclay.com wrote:
> I've seen an artist who has flexible molds of female figures that are
> at
> least 24" x 8" x 8" and pushes clay up into the mold including the head
> and neck area. Then peels the mold off the piece and continues to
> manipulate the sculpture.
You can use rubber molds for press-molding clay.
Nan Smith uses this technique extensively. It is not
difficult to learn to make a rubber mold, but it is
time-consuming and rather expensive, and requires
good attention to craftsmanship. I presently use
Smooth-On Rubber's ' 50/50' urethane product, as it
is less fussy in measurement, though less versatile
than the more exacting varieties of urethane mold
rubber. There are other companies that make equally
good products for this purpose. Some people prefer
silicone, but I think it is better for small poured-in-a-
container molds, not larger 'laid-up' molds. Latex is
readily available in most hobby/art supply stores, but
has serious drawbacks in my opinion. Still, it might
serve as a learning material. If you try latex, look for
the non-ammonia (non-fume) type. I used to buy through
Douglas & Sturgess in San Francisco when I lived out
that way, but you should look or a close-by supplier, as
shipping can add up. You should also buy soon, as
many of these products are not shippable during the
freeze season.
Flexible rubber molds of all types need a 'jacket' of a
rigid material to keep them from deforming like a water
balloon. Plaster is my preference, though some people
use fiberglass, which is lighter, but icky.
Practice on something small, and get the hand of the
stuff before starting on something large. Do some research
and make sure it's the process you need before investing
in materials.
A full explanation could run on for pages, so I won't get
into it here. Feel free to ask if you have specific questions,
though.
-Snail
Don Fuchs on thu 6 nov 08
Hi Anna,
I have seen some mold like you describe made out of latex then backed
with plaster. The latex is applied in many layers over many days. I have
used a RTV polyurethane castable rubber from Polytek Co. in Easton, PA
(http://www.polytek.com/). Both materials may do what you want. A technique
I've had success with is to cut up a soda can to use as shims to press into
the clay model then cast rubber into the sectioned off space. I suggest
experimenting your technique on a small expendable piece. It's easy to get
frustrated with new materials on a new process. All the best, Don Fuchs
www.agapepottery.com
Date: Wed, 5 Nov 2008 17:37:28 -0500
From: "ann@annbclay.com"
Subject: flexible molds
I am trying to find a way to make molds of some 3d, 360 degree sculpture
parts but need them to remain workable (leather hard) after removing
from the mold. (they do not need to be hollow, but will have undercut
areas)
I've seen an artist who has flexible molds of female figures that are at
least 24" x 8" x 8" and pushes clay up into the mold including the head
and neck area. Then peels the mold off the piece and continues to
manipulate the sculpture. Does anyone know more about this type of
technique or have recommendations on other techniques I can look into?
Any books or printed materials available?
Thanks,
annb
--
www.annbclay.com
Ann Burdette Baker
331 Old Tory Trail
Aiken, SC 29801
"I am always doing things I can't do, that is how I get to do them."
--Pablo Picasso
Jeff Longtin on thu 6 nov 08
Hey Ann,
Several years ago I made rubber molds for a doll artist and she does exactly
what you describe. (On a smaller scale of course.)
Previously I didn't think rubber was a suitable material for water-based
clay but she proved me wrong.
I molded several of her doll heads in a urethane rubber from Polytek. She
asked that they be thick to endure the pressure from her pressing stiffer clay
into the forms.
The situation you describe would call for a strong backing mold. (a mother
mold, as it were.) Plaster is cheap but awfully heavy in larger sizes. You
could try a casting plaster, as opposed to a "pottery" plaster, to lighten the
weight a little, but a resin material is probably your lightest/strongest
chioce.
Smooth-On also makes great urethane casting rubber.
good luck
Jeff
In a message dated 11/5/2008 5:02:58 P.M. Central Standard Time,
ann@ANNBCLAY.COM writes:
I am trying to find a way to make molds of some 3d, 360 degree sculpture
parts but need them to remain workable (leather hard) after removing
from the mold. (they do not need to be hollow, but will have undercut
areas)
I've seen an artist who has flexible molds of female figures that are at
least 24" x 8" x 8" and pushes clay up into the mold including the head
and neck area. Then peels the mold off the piece and continues to
manipulate the sculpture. Does anyone know more about this type of
technique or have recommendations on other techniques I can look into?
Any books or printed materials available?
Thanks,
annb
--
www.annbclay.com
Ann Burdette Baker
331 Old Tory Trail
Aiken, SC 29801
"I am always doing things I can't do, that is how I get to do them."
--Pablo Picasso
**************AOL Search: Your one stop for directions, recipes and all other
Holiday needs. Search Now.
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-aol-search/?ncid=emlcntussear00000001)
John Rodgers on thu 6 nov 08
Ann,
This a bit long, but here goes.
There are many different ways to make molds -
Ridgid Molds - typically made from plaster. These hold up well, but if
the model is complex and has undercuts, then it takes some doing ot get
one right.
Flexible Molds -
1) Latex Rubber - latex is brushed on over the model in multiple layers
to build up a shell. Each layer dries before the next is applied. This
method will pick up detail very nicely. When done, if the model is
rigid, you can just peel the latex from the model like removing a sock
from the foot. Because of the flexibility of the material, however, you
need to make a "Mother" mold around the latex before it is removed from
the model. This can be done with plaster, or with fiberglas, or some of
the hard-setting urethane foams like furniture foams. For very small
pieces, you can make a mother mold out of the two-part plumbers putty
you can buy at the hardware store. Usually just cut equal parts off the
two rolls in the box, squish the together well in your hands ( they are
not sticky), then flatten the material into a sheet and press onto the
latex. BE SURE TO USE A RELEASE AGENT LIKE POLYEASE 2300 or you will
bind your mold to the resin shell.
Brushable Rubber - these are two part rubber compounds that when mixed
are of a like a very soft peanut butter consistency. Spray coat your
model with Polyease 2300 or similar silicone mold release. Apply brush
coats over the model with a brush. When the rubber is cured, make a
mother mold as described for latex molds. PolyTek carrys brushable
rubber compounds, as does Smooth-on. I'm sure there are others.
Pourable Rubber. - I use the PolyTek pourables - Though I have used
others, I just like their performance best. They come as a resin in one
can, (Part A) and a catalyst(Part B) in another. There is a Part C that
can be added which slows setting time and makes the rubber brushable.,
but I have never had the occasion to use this material. Some rubbers
mix in a 1 to 1 ratio, others mix in a 10 to 1 ratio. Both have their
uses, and I have used both. The 10 to 1 is a bit more of a hassle, but
is cheaper, as I recall, than the 1:1 stuff. It all depends on your
needs. One way of making a mold on a model is to wrap the piece in Saran
Wrap, then roll out a sheet of *Sulphur Free* - I cannot emphasize that
enough "Sulphur Free* - oil clay to a thickness of 3/8 to 1/2 in
thickness. Using this clay, press the sheets of clay on the surface of
the Saran wrap, and join the edges so the model is completely sealed in.
Next, create a mother mold over the oil clay. Make it from plaster, and
make it in two parts - a right and a left half. With a mix of 50/50
water and Murphys Oil Soap from the hardware store, or tincture of Green
Soap from the Drugstore, sponge it on the edge of the plaster then brush
dry with a heap throwaway china bristle brush from the pain store.
Repeat the process 3 to 4 times. This ensures the new plaster won't
stick to the old. You can make a plaster paste and work it to the
surface. It needs to be at least an inch thick if the model is fairly
large, or perhaps even thicker, depending. Here, experience is the
guide. I can look at a piece and have a good idea as to how thick -
therefore strong - it must be, but I would not presume to tell anyone
over the internet about how to do this. One must educate one's eyeball.
When the plaster is set, turn the mold and mother upside down, and now
make a bottom piece - a foot as it were. and cut some keyways into the
existing plaster bottom. This will ensure the mother mold lines up
correctly every time. Again use 50/50 water with Murphy's Oil Soap or
Tincture of green soap from the drugstore. and with a sponge soak that
bottom edge of the plaster mother mold. Work up a lather with the
sponge. Then, with a cheap throwaway china bristle paint brush from the
paint section in the hardware store, brush that plaster dry, until there
is no soap shine. Do this 3-4 times. now create that plaster bottom.
Remove this mother mold, and allow it to dry thoroughly. You do not want
the slightest hint of moisture present. Urethanes are extremely reactive
with water and will swell beyond belief if they are wet before the
curing takes place. It is the introduction of a little moisture that
makes the urethane foams-in-a-can work. Spray the can and introduce a
little moisture and the stuff goes crazy. I made the mistake of using
vaseline as a mold release, not realizing that Vaseline has a moisture
content. The poured urethane reacted with the water in the vaseline,
swelling out of the mold form, swelled across the table, onto the floor,
and kept getting bigger and biger and bigger. Had to move the furniture
out to prevent a totally unmanageable mess. It looked like "The Blob"
had come to visit. You DO NOT want to experience the expansion and the
stickiness of water activated urethanes. The stuff adheres to anything,
and it will not let go. Much worse that Uncle Remus' Tarbaby. And it
stays sticky/gooey - won't cure. It took me weeks to finally get it all
up and cleared from the work space. - and off of everything.
After the mother mold is thoroughly dry, from the inside of the plaster
mother mold. drill a few 1/2 inche holes about 1/2 inche deep around the
inside surface of the plaster. These will become registration keys to
hole the rubber in place. and keep it from moving around once cured.
Throughly seal the surfaces of the plaster, inside and out, with the
soap mix, brushing dry between coats.
Assemble the mother mold, without the model inside. Make some holes in
the very top through which to pour rubber and to vent the mold.
Again seal any plaster cuts with the soap mix.
Remove the oil clay and the Saran wrap from the model. Save the clay -
you will need to weigh it.
Again coat the model with another coat of Polyease 2300 silicone mold
release. Brushit out with a good quality china bristle brush. Be sure no
bristles come out of the brush in the process.
Open the mother mold, and rub down the surfaces with a dry rag.
Spray three coats of urethane varnish on the inside surfaces, and allow
to dry thoroughly between each coat.
Re-assemble the Mother mold with base around the model. Strap it
together with mold belts. Seal all edges of the mold with oil clay -
non-sulphurous type.
Now, estimate your total rubber requirement. To do this, roll out some
of that clay you saved. measure off a one cubic or two cubic inch block,
then weigh it. Using the total weight of the clay, and the weight of the
one cubic inch block, you can use the specifications data on the rubber
to calculate approximately how much rubber you will need to mix. Because
urethane rubber compounds are so expensive, you will certainly want to
do this. But to be safe, always mix just a bit more to allow for errors.
Otherwise you wind up with only a partial rubber mold, and that wastes
material, time and money. DON'T ask me how I know so well. Take my word
for it.
The Shore Hardness of the rubber can be varied by varying the
catalyst/resin ration, so this needs to be thought out ahead. If you
want a very flexy mold, this it must be planned for.
Mix your rubber according to your needs, then pour slowly in a steady
solid stream. The pressure of the pour will help drive out air that
might tend to get mixed in. The urethane is fairly viscous so you want
to avoid entrapping air during the pour. Allow it to work out during the
pouring.
After done, check for leaks around the edges. Stick on more clay if
needed. A leak means and air bubble can form inside. It can become
trapped and you don't want a big air pocket right next to to your piece.
Weight 24 hours for the rubber to cure, then remove the mother mold.
Depending on how it was all set up, the rubber can be just peeled back
like a sock, or you may have need of cutting a parting line in the
materials - it's hard to say without having a specific pieces to work
with. But there are considerations for every piece.
So, that is the Urethane mold rubber story.
]
Silicone rubbers work similarly, but can be a bit more aggravating where
air entrainment is concerned. Many moldmakers use a vacuum machine to
remove air from the silicone rubber before pouring.
Hope all this is of help.
Regards,
John Rodgers
Chelsea, AL
ann@annbclay.com wrote:
> I am trying to find a way to make molds of some 3d, 360 degree sculpture
> parts but need them to remain workable (leather hard) after removing
> from the mold. (they do not need to be hollow, but will have undercut
> areas)
>
> I've seen an artist who has flexible molds of female figures that are at
> least 24" x 8" x 8" and pushes clay up into the mold including the head
> and neck area. Then peels the mold off the piece and continues to
> manipulate the sculpture. Does anyone know more about this type of
> technique or have recommendations on other techniques I can look into?
> Any books or printed materials available?
>
> Thanks,
> annb
>
> --
>
> www.annbclay.com
>
> Ann Burdette Baker
> 331 Old Tory Trail
> Aiken, SC 29801
>
> "I am always doing things I can't do, that is how I get to do them."
> --Pablo Picasso
>
>
John Rodgers on fri 7 nov 08
I forgot to mention - latex is notorious for shrinking over time. - at
least the common stuff you get at the hobby shops, and even some ceramic
supply houses., etc, You will need to do some serious shoppng to find
one that doesn't shrink, but they are out there. Just don't get
surprised when your mold made from the lower grade materials changes or
loses shape or is smaller after time.
John Rodgrets
Chelsea, AL
John Rodgers wrote:
> Ann,
>
> This a bit long, but here goes.
>
> There are many different ways to make molds -
>
> Ridgid Molds - typically made from plaster. These hold up well, but if
> the model is complex and has undercuts, then it takes some doing ot get
> one right.
>
> Flexible Molds -
>
> 1) Latex Rubber - latex is brushed on over the model in multiple layers
> to build up a shell. Each layer dries before the next is applied. This
> method will pick up detail very nicely. When done, if the model is
> rigid, you can just peel the latex from the model like removing a sock
> from the foot. Because of the flexibility of the material, however, you
> need to make a "Mother" mold around the latex before it is removed from
> the model. This can be done with plaster, or with fiberglas, or some of
> the hard-setting urethane foams like furniture foams. For very small
> pieces, you can make a mother mold out of the two-part plumbers putty
> you can buy at the hardware store. Usually just cut equal parts off the
> two rolls in the box, squish the together well in your hands ( they are
> not sticky), then flatten the material into a sheet and press onto the
> latex. BE SURE TO USE A RELEASE AGENT LIKE POLYEASE 2300 or you will
> bind your mold to the resin shell.
>
> Brushable Rubber - these are two part rubber compounds that when mixed
> are of a like a very soft peanut butter consistency. Spray coat your
> model with Polyease 2300 or similar silicone mold release. Apply brush
> coats over the model with a brush. When the rubber is cured, make a
> mother mold as described for latex molds. PolyTek carrys brushable
> rubber compounds, as does Smooth-on. I'm sure there are others.
>
> Pourable Rubber. - I use the PolyTek pourables - Though I have used
> others, I just like their performance best. They come as a resin in one
> can, (Part A) and a catalyst(Part B) in another. There is a Part C that
> can be added which slows setting time and makes the rubber brushable.,
> but I have never had the occasion to use this material. Some rubbers
> mix in a 1 to 1 ratio, others mix in a 10 to 1 ratio. Both have their
> uses, and I have used both. The 10 to 1 is a bit more of a hassle, but
> is cheaper, as I recall, than the 1:1 stuff. It all depends on your
> needs. One way of making a mold on a model is to wrap the piece in Saran
> Wrap, then roll out a sheet of *Sulphur Free* - I cannot emphasize that
> enough "Sulphur Free* - oil clay to a thickness of 3/8 to 1/2 in
> thickness. Using this clay, press the sheets of clay on the surface of
> the Saran wrap, and join the edges so the model is completely sealed in.
> Next, create a mother mold over the oil clay. Make it from plaster, and
> make it in two parts - a right and a left half. With a mix of 50/50
> water and Murphys Oil Soap from the hardware store, or tincture of Green
> Soap from the Drugstore, sponge it on the edge of the plaster then brush
> dry with a heap throwaway china bristle brush from the pain store.
> Repeat the process 3 to 4 times. This ensures the new plaster won't
> stick to the old. You can make a plaster paste and work it to the
> surface. It needs to be at least an inch thick if the model is fairly
> large, or perhaps even thicker, depending. Here, experience is the
> guide. I can look at a piece and have a good idea as to how thick -
> therefore strong - it must be, but I would not presume to tell anyone
> over the internet about how to do this. One must educate one's eyeball.
> When the plaster is set, turn the mold and mother upside down, and now
> make a bottom piece - a foot as it were. and cut some keyways into the
> existing plaster bottom. This will ensure the mother mold lines up
> correctly every time. Again use 50/50 water with Murphy's Oil Soap or
> Tincture of green soap from the drugstore. and with a sponge soak that
> bottom edge of the plaster mother mold. Work up a lather with the
> sponge. Then, with a cheap throwaway china bristle paint brush from the
> paint section in the hardware store, brush that plaster dry, until there
> is no soap shine. Do this 3-4 times. now create that plaster bottom.
>
> Remove this mother mold, and allow it to dry thoroughly. You do not want
> the slightest hint of moisture present. Urethanes are extremely reactive
> with water and will swell beyond belief if they are wet before the
> curing takes place. It is the introduction of a little moisture that
> makes the urethane foams-in-a-can work. Spray the can and introduce a
> little moisture and the stuff goes crazy. I made the mistake of using
> vaseline as a mold release, not realizing that Vaseline has a moisture
> content. The poured urethane reacted with the water in the vaseline,
> swelling out of the mold form, swelled across the table, onto the floor,
> and kept getting bigger and biger and bigger. Had to move the furniture
> out to prevent a totally unmanageable mess. It looked like "The Blob"
> had come to visit. You DO NOT want to experience the expansion and the
> stickiness of water activated urethanes. The stuff adheres to anything,
> and it will not let go. Much worse that Uncle Remus' Tarbaby. And it
> stays sticky/gooey - won't cure. It took me weeks to finally get it all
> up and cleared from the work space. - and off of everything.
>
> After the mother mold is thoroughly dry, from the inside of the plaster
> mother mold. drill a few 1/2 inche holes about 1/2 inche deep around the
> inside surface of the plaster. These will become registration keys to
> hole the rubber in place. and keep it from moving around once cured.
>
> Throughly seal the surfaces of the plaster, inside and out, with the
> soap mix, brushing dry between coats.
>
> Assemble the mother mold, without the model inside. Make some holes in
> the very top through which to pour rubber and to vent the mold.
>
> Again seal any plaster cuts with the soap mix.
>
> Remove the oil clay and the Saran wrap from the model. Save the clay -
> you will need to weigh it.
>
> Again coat the model with another coat of Polyease 2300 silicone mold
> release. Brushit out with a good quality china bristle brush. Be sure no
> bristles come out of the brush in the process.
>
> Open the mother mold, and rub down the surfaces with a dry rag.
>
> Spray three coats of urethane varnish on the inside surfaces, and allow
> to dry thoroughly between each coat.
>
> Re-assemble the Mother mold with base around the model. Strap it
> together with mold belts. Seal all edges of the mold with oil clay -
> non-sulphurous type.
>
> Now, estimate your total rubber requirement. To do this, roll out some
> of that clay you saved. measure off a one cubic or two cubic inch block,
> then weigh it. Using the total weight of the clay, and the weight of the
> one cubic inch block, you can use the specifications data on the rubber
> to calculate approximately how much rubber you will need to mix. Because
> urethane rubber compounds are so expensive, you will certainly want to
> do this. But to be safe, always mix just a bit more to allow for errors.
> Otherwise you wind up with only a partial rubber mold, and that wastes
> material, time and money. DON'T ask me how I know so well. Take my word
> for it.
>
> The Shore Hardness of the rubber can be varied by varying the
> catalyst/resin ration, so this needs to be thought out ahead. If you
> want a very flexy mold, this it must be planned for.
>
> Mix your rubber according to your needs, then pour slowly in a steady
> solid stream. The pressure of the pour will help drive out air that
> might tend to get mixed in. The urethane is fairly viscous so you want
> to avoid entrapping air during the pour. Allow it to work out during the
> pouring.
>
> After done, check for leaks around the edges. Stick on more clay if
> needed. A leak means and air bubble can form inside. It can become
> trapped and you don't want a big air pocket right next to to your piece.
>
> Weight 24 hours for the rubber to cure, then remove the mother mold.
>
> Depending on how it was all set up, the rubber can be just peeled back
> like a sock, or you may have need of cutting a parting line in the
> materials - it's hard to say without having a specific pieces to work
> with. But there are considerations for every piece.
>
> So, that is the Urethane mold rubber story.
> ]
> Silicone rubbers work similarly, but can be a bit more aggravating where
> air entrainment is concerned. Many moldmakers use a vacuum machine to
> remove air from the silicone rubber before pouring.
>
> Hope all this is of help.
>
> Regards,
>
> John Rodgers
> Chelsea, AL
>
>
>
>
>
>
>
>
> ann@annbclay.com wrote:
>> I am trying to find a way to make molds of some 3d, 360 degree sculpture
>> parts but need them to remain workable (leather hard) after removing
>> from the mold. (they do not need to be hollow, but will have undercut
>> areas)
>>
>> I've seen an artist who has flexible molds of female figures that are at
>> least 24" x 8" x 8" and pushes clay up into the mold including the head
>> and neck area. Then peels the mold off the piece and continues to
>> manipulate the sculpture. Does anyone know more about this type of
>> technique or have recommendations on other techniques I can look into?
>> Any books or printed materials available?
>>
>> Thanks,
>> annb
>>
>> --
>>
>> www.annbclay.com
>>
>> Ann Burdette Baker
>> 331 Old Tory Trail
>> Aiken, SC 29801
>>
>> "I am always doing things I can't do, that is how I get to do them."
>> --Pablo Picasso
>>
>>
>
>
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