plasticine clay Q? - WarmGlass.com

plasticine clay Q?

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rosanna gusler
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plasticine clay Q?

Postby rosanna gusler » Wed Mar 31, 2004 8:10 am

does plasticine release easily from plaster? i have this sort of bas relief (sp) fish idea that i want to kiln cast. my idea is that i will sculpt my fish out of plasticine and make a plaster mold. then i will cast plaster in that mold so i have a copy of my fish that i can use to make multiple plaster silica molds to use in the kiln. clear as mud? rosanna

Brock
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Postby Brock » Wed Mar 31, 2004 9:52 am

Yes it does. Go for it. Brock
My memory is so good, I can't remember the last time I forgot something . . .

charlie holden
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Postby charlie holden » Wed Mar 31, 2004 1:04 pm

Depending on the details, you might want to cast your model in rubber or silicone instead of plastic. If so make sure that the rubber you choose will work with the plasticine. Some plasticines have sulfur in them and some rubber mixes react to sulfur. I don't know if this is a problem with silicone or not.

ch

rosanna gusler
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Postby rosanna gusler » Wed Mar 31, 2004 1:36 pm

i thought about that but i have plaster. the OBX is BFE when it comes to shopping. i had to order the plasticine from ace hardware. we do not have michals stores or anything like that. rosanna

Lauri Levanto
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Postby Lauri Levanto » Wed Mar 31, 2004 3:25 pm

Plasticine clay, plaster and waterbased clay do not
stick to each other.

Im nodeling I work in waterbased clay. If I need a partitioned mould, I build the wall of plasticine. over the clay piece. Then I cast the first side, remove the wall,
add release soap to the seam and cast the second part.

Hard plasticine may be difficult to carve out from a mould. Heat it carefully.
-lauri

rosanna gusler
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Postby rosanna gusler » Wed Mar 31, 2004 3:43 pm

i thought about using clay clay. i have about 500 lbs of various types. i just thought the plasticine would be easier as i would not have to worry about it drying. this will be an open face mold no undercuts. the plasticine should just pop out of the plaster i assume. rosanna

Rebecca M.
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Postby Rebecca M. » Wed Mar 31, 2004 4:14 pm

I was messing around yesterday with my very first mold making, and I used some Sculpy clay that doesn't get hard unless you bake it in the oven. I'm not sure if that is like plasticene or not. It pulled right out of the mold, but got messed up. And it left a very good impression. I did have a problem with it being seated properly because the mold mix leaked under a bit. I didn't want to squash it down too hard and lose any definition and was picking plaster off around the edges before I could lift it out. I have some fine tuning to do, but it worked OK, just can't wait too long before flipping and getting the stuff out.

Bert Weiss
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Postby Bert Weiss » Wed Mar 31, 2004 8:22 pm

Rosanna

The hard part is seperating plaster from plaster. You need to soap the original mold and even then I've seen them seperated by intensely blowing compressed air at the interface.

I'm with Charlie. Make a rubber mold in which to cast your plaster/silica. Once you've worked with rubber, there is no alternative even close.

Smooth on in New Jersey makes dozens of different rubbers for this purpose. The best one I used has a release built in to the rubber. The cheapest is a paint on that requires a plaster mother.
Bert

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Lauri Levanto
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Plasticine

Postby Lauri Levanto » Thu Apr 01, 2004 1:49 am

After thinking overnight
I remembered one more caveat.
If you take the final mould from plasticine,
please note that plasticine is oil based.
Some of this oil may seep into your mould.
It is better to burn the oil residue out before casting.

If you are frit casting, nad ramp up slowly
I expect the oil combust before the glass is sealed.
If you cast a large blank, that may give you
bubbles lined with black soot.
At least I got some.

-lauri

rosanna gusler
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Postby rosanna gusler » Thu Apr 01, 2004 1:20 pm

i ordered a couple of smooth on brushable test kits. i like the idea of rubber with a plaster mother mold to make my multiple casting molds. rosanna

Rebecca M.
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Postby Rebecca M. » Sat Apr 03, 2004 10:21 am

I found a couple of interesting how-to sites while I was searching for what I did wrong. Turns out everything I guess, or at least backwards. Anyway these have pictures and text, and seem to be pretty good if you're making small molds.

http://www.mouldmaking.freeserve.co.uk/

http://www.hirstarts.com/moldmake/moldmaking.html

I guess the rubber IS the thing. Of course I picked it up and put it back down when I was at Pearl last weekend. :roll:

Bert Weiss
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Postby Bert Weiss » Sat Apr 03, 2004 2:49 pm

Becca wrote:I found a couple of interesting how-to sites while I was searching for what I did wrong. Turns out everything I guess, or at least backwards. Anyway these have pictures and text, and seem to be pretty good if you're making small molds.

http://www.mouldmaking.freeserve.co.uk/

http://www.hirstarts.com/moldmake/moldmaking.html

I guess the rubber IS the thing. Of course I picked it up and put it back down when I was at Pearl last weekend. :roll:


A few points on why rubber rules. For one thing it is difficult to remove all of the clay, either plasticene or regular wet clay. The places where there is clay residue on the mold require cold working because the glass surface is effected. If you go to the trouble of washing out the mold, you can also mess up the surface of the investment. Another is the easy repeatability with a rubber mold. The rubber is flexible, so it is easily removed once the investment has hardened.

I've used both the solid rubber and the paint on rubber with a plaster mother. The plaster serves to keep the rubber in shape. The paint on is much less stable and trickier to use. The solid rubber positive for making bas relief molds is a wonderful thing. I would glue the rubber positive on to a rubber sheet with 2 part rubber epoxy, then place a wooden frame on the rubber. First you do a little pour to seal the frame, then your cover coat, then your mold pour.

Today, I would be seriously looking at using vermiculite board as part of the process.

If you want to do lost wax casting, rubber molds are also good for making waxes in.
Bert



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rosanna gusler
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Postby rosanna gusler » Sat Apr 03, 2004 4:01 pm

hmmmmm vermiculite board.....now that is something to think about. in stock too. lol. rosanna


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