Re: Hydroperm Plaster


Bramblebush ForumsFAQ

Posted by joew on January 15, 19100 at 18:20:53:

In Reply to: Re: Hydroperm Plaster posted by Jesse Brennan on January 14, 19100 at 09:01:22:

Maybe you can get by with a shell-core.. much lighter with it's hollow core and less material to dry out. Most of your venting might be taken care of with the the core's center cavity.

They are light and air-filled, prone to floating in the metal. Strong support could take care of that.

I guess it all depends on the shape/size/thicknesses, etc of the entire project. A shell core has to have a minimum thickness to just hold itself together under whatever conditions..

btw, evidently I reinvented the wheel with the foamed plaster idea.

Saw a recipe for foamed investments.. 1 part molding plaster/3 parts silica flour. The mix is added to an equal weight of water, 1 to 1 ratio... add a squirt of dishwashing soap, and mix till its firm.. Saw this in Ammen's newest 'Metalcasting' copyright 2000.. I got a couple books at

One can vary the amount/size of bubbles by the speed and time of mixing, and the ammount of soap. The few experiments i did would support even coarse sand, but by that time you have only a minute to pour, before it sets up.. Starts to set up as soon as you stop mixing.

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