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Old 11-03-2012, 05:53 PM
royboy royboy is offline
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Join Date: Jul 2009
Location: Ireland
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Clay to bronze - shrinkage

Hi all, Is there a formular for predicting the shrinking ratio of a life sized clay sculpture once it has been moulded and cast in bronze using the lost wax method? Also what do most sculptors suggest when writting up a proposal for a commemorative sculpture; life size, life+half, life and a 1/4?
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Old 11-03-2012, 06:31 PM
Andrew Werby Andrew Werby is offline
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Location: Oakland, CA
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Re: Clay to bronze - shrinkage

Is this potter's clay (water-based) or plasticine (oil-based)? Potter's clay shrinks more, especially if it's fired. Different mold materials and casting techniques also have different shrinkage rates.

I think the usual nomenclature for enlarged people is life-sized, heroic size, and colossal size, but I'm not sure what the precise measurements would be.

Andrew Werby
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Old 11-04-2012, 06:54 AM
Mack Mack is offline
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Re: Clay to bronze - shrinkage

I think an approximate amount of shrinkage is 1/4" for evey 12" of your model.
Doesn't matter what the material of your model is since it will be molded, the shrinkage will take place over the next two stages: wax and then bronze. Regarding terms like life-size, monumental etc, which are very general, best to just give a close approximation of what the actual finished bronze will be.
Good Luck!
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Old 11-04-2012, 05:23 PM
raspero raspero is offline
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Re: Clay to bronze - shrinkage

Wax shrinks a lot when it solidifies, but almost all of the shrinkage seems to happen in the thickness. The shape of the piece holds it in place in the rubber mold and doesn't allow it to shrink in the other dimensions. The standard foundry allowance for bronze shrinkage is as Mack said.

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