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Old 02-04-2009, 01:23 AM
Mr. Malloy's Avatar
Mr. Malloy Mr. Malloy is offline
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casting mannequin parts

I am trying to make molds to cast some mannequin parts. The parts are fragile and older plastic. Can I just use plaster right on them with, say, vasoline as a release agent? I intend to make plaster and concrete forms from these molds. I don't have the money and am not worried about fine detail so I will not use a silicone rubber mold under the plaster. I ask all this becouse I do not want to destroy the parts in the process. Any one try this before?
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Old 02-04-2009, 09:04 AM
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ahirschman ahirschman is offline
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Re: casting mannequin parts

If you value the parts, then you would probably use some type of flexible mold. You are always taking a risk when using rigid materials.

You would not need that much rubber (much cheaper than silicone) to make molds of parts like you describe. You would still have to make a nice plaster mother mold to support your rubber.

I have cast into plaster and have had adhesion problems (Sometimes) even when using a release.

Also, you will have to be very careful if you use a hard material to make sure you do not have undercuts and embed your part in the plaster.

On a hand, if you cast a two part mold and go over the middle of a finger (If you think of the finger as a cylinder) the you will lock it into the mold. You would have to make a mold with many more parts than if you used rubber.

Remember you can get by with only 3 or 4 mm of rubber, so you can go a long way. The only area where you will use up more rubber is along the seam, but you can always trade time for $ and vise versa. If you are careful with your mold design you can end up using very little of the expensive materials.

Hope this helps.

Ari.
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Old 02-04-2009, 01:12 PM
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Mr. Malloy Mr. Malloy is offline
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Re: casting mannequin parts

Thanks. I have done some plaster ,two-part molds in the past and know that you can not go beyond the half way point or the piece will be in there stuck. I am hoping to make multiples of these parts so I need to re-use the molds and I'll try the rubber-under the mother mold process but even so. That stuff is 100 buck a gallon from smooth-on. and I shopped around a lot. Even the industrial supply places I found that have soft rubber mold making supplies are at least that much. Thanks again.
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Old 02-05-2009, 10:42 PM
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ahirschman ahirschman is offline
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Re: casting mannequin parts

I think you could do it with just plaster, but to do it correctly you would spend a lot of time. If you buy a gallon of rubber, then you will have enough to cover 8 square feet (approximately), at 5mm thickness. That should be enough to make 8 to 10 molds of hands and feet. Again, you will have to exchange time for $ by being more careful in the use of the rubber. That is about $15 per mold, including the plaster for the mother mold. That does not sound so bad.

Ari
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