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Frank Gorenstein
Joined:
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09-Jul-2004
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Started On : 05-Aug-2006 at 01:00:01 AM, #Views : 5973
Topic Subject : Re: Re: Mixing Gypsum |
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Ok, I use both H-Stone and H-Cal in my business for many years, both have their good points and bad points. H-Stone is a Super Cement that does contain Portland. It is very strong when mixed and dried correctly. It is designed to fill a mold completely and not good for slush casting. When it kicks, it kicks instantly. There are several other ways to use H-Stone with other materials to get a thin hard casting, but require a good knowledge of the other materials to use it with.
H-Cal on the other hand can be slush cast and pushed around. You can use cheese cloth or burlap for added strength. You can add some H-Stone (20%) to increase the hardness and strength properties without losing the other properties. You can also add some white Portland (5%) and do the same thing.
As for drying, you do have to provide air circulation and heat for ultimate strength. I have a drying room with a fan and a heater that I use.
You might consider checking out Ciment Fondue and Secar 71, which is readily available in the UK.
Hydrostone Spec's
Use Consistency 32 parts of water by weight per 100 parts plaster
1 Hr. Compressive Strength 4,000 psi
Dry Compressive Strength 10,000 psi
Maximum Setting Expansion 0.240%
Density Wet 119.0 lb/ft3
Dry 108.0 lb/ft3 1.73
Set Time (Machine Mix)* 17-20 min.
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Hello Frank Gorenstein
Post Date : Friday 04th of August 2006 11:58:04 PM
Posted by : "Diane Rossong" Diane@lastingimpression.net
Re: Re: Mixing Gypsum:--
Thanks for pointing that out. I can only use it on my solid casts then.(hands/feet)
I will try hydrocal wh for for my other casts.
But if you go on usg's website gypsumsolutions.com that is where I got that info. The gypsums that I looked at all have silica in it. Look at their safety data sheets you can find out what is in all of their gypums. so using a resporator/dust mask if sanding or tooling is probably a good idea.
It also says that their gypsums should be put into some sort of drying chamber or room "to get the maximum physycal properties to develope" with heat and ventalation. I really am hoping that it can dry on its own over a period of time.
Diane
ALI is an international organization whose members are engaged in the art and creative industries. Its purpose is to promote the art of life casting, create public awareness of this unique art form, provide its members with forums to exchange information, resources to enhance their effectiveness and advance opportunities for their artistic success.
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