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Hardware plaster for hump mold?


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#1 Biglou13

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Posted 10 May 2013 - 11:44 AM

Just making simple hump mold.

Can I use plaster o Paris from hardware store?

What's the difference with fancy stuff from ceramic supply?
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#2 Denice

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Posted 10 May 2013 - 12:30 PM

Big Lou I was just doing some research on that subject, I have a project that calls for plaster of paris I always have a bag of pottery plaster around and it's a lot cheaper than plaster of paris. Around here pottery plaster is 7 dollars for 50 lbs. and 20 for 25 lbs plaster of paris. Pottery plaster is harder more durable and less absorbent and is considered a higher quality plaster. For a hump mold I would go for the pottery plaster for durability and less absorbent. Denice

#3 Biglou13

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Posted 10 May 2013 - 01:08 PM

USG#1. Is only 20.50/ 50# bag plus a 45 min drive. And the danger to wallet for going to toy store. (US gypsum)


$ 15/25# plaster o Paris. @home depot.

(What's Paris got to do wit it?)
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#4 AtomicAxe

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Posted 10 May 2013 - 03:07 PM

Home depot plaster is ment for softer applications like patching or covering walls, stuff like that ... as such it tends to not be nice for things like slip molds ... but really ... if you don't abuse the snot out of it you shouldn't have to worry anyways. I have a plaster mold that has to be 9 years old, just as nice as the first day I made it. Oh and if you are going to make a big mold ... put some fiber in it, it helps.

#5 Biglou13

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Posted 10 May 2013 - 03:24 PM

Home depot plaster is ment for softer applications like patching or covering walls, stuff like that ... as such it tends to not be nice for things like slip molds ... but really ... if you don't abuse the snot out of it you shouldn't have to worry anyways. I have a plaster mold that has to be 9 years old, just as nice as the first day I made it. Oh and if you are going to make a big mold ... put some fiber in it, it helps.


Metamucil?

What do you use for fiber?

It's only 15 ish inches diameter ish. Read about hardware cloth and scrim cloth.

I have a few sheets of drywall sanding screen I'm going reinforce with.

Thanks all for the 411

PS. Large gypsum deposit at Montmartre in Paris led "calcined gypsum" (roasted gypsum or gypsum plaster) to be commonly known as "plaster of Paris". Ala Webster/Wikipedia.......
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#6 Marcia Selsor

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Posted 10 May 2013 - 05:44 PM

The US#1 Plaster is worth it.
As Ben Franklin use to say "Penny wise and dollar foolish". Sometimes you need to pay for the quality you need.

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#7 BeckyH

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Posted 10 May 2013 - 06:29 PM

For casting, #1 plaster is the best. For hump molds, plaster of Paris should work just fine. I have seen people use carved closed-cell foam for hump molds, if you want cheap and carveable.

#8 AtomicAxe

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Posted 11 May 2013 - 12:55 AM


Home depot plaster is ment for softer applications like patching or covering walls, stuff like that ... as such it tends to not be nice for things like slip molds ... but really ... if you don't abuse the snot out of it you shouldn't have to worry anyways. I have a plaster mold that has to be 9 years old, just as nice as the first day I made it. Oh and if you are going to make a big mold ... put some fiber in it, it helps.


Metamucil?

What do you use for fiber?

It's only 15 ish inches diameter ish. Read about hardware cloth and scrim cloth.

I have a few sheets of drywall sanding screen I'm going reinforce with.

Thanks all for the 411

PS. Large gypsum deposit at Montmartre in Paris led "calcined gypsum" (roasted gypsum or gypsum plaster) to be commonly known as "plaster of Paris". Ala Webster/Wikipedia.......


Sorry, I thought I should be more specific but forgot to be. Loose fiberglass fiber is what I was refering to.




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