Re: CASTING Plaster Investments vs. Ceramic Shell?????


Bramblebush ForumsFAQ

Posted by bpfink on February 12, 1999 at 00:28:36:

In Reply to: Re: CASTING Plaster Investments vs. Ceramic Shell????? posted by John Stricklin on February 11, 1999 at 21:14:37:

I'd go for it and see what happens. Sounds good to me.

The plaster based investment uses the plaster as the binder of the sands and fillers. The plaster will break down but will not necessarily move or loose the sand bodies shapes, thus

the mold keeps it's shape.

Actually this can be an advantage since the removal of it later is easy compared to many others. A lump of the burned out mold can be crushed to powder in your hand ... so do

remember to wrap or cast the investment in a wire cage so you can handle it.

I use 1 inch mesh chicken wire. and the molds can be up to 1000 or more pounds and still lifted out and turned over to pour.

I use plaster based molds for the lost wax process and when they are fully burned out at the higher temperatures they still work fairly well (some flashing may show up the higher and longer they are fired but we are talking days here not just an hour).

As for the commercial investments, they are often just mixes made in the back room of a warehouse (or such until sales get worth the bigger manufacture mixing) and you can certainly do the same.

I once took the sample from a dental investment mix and mixed it in a test tube with 10 times the water.

Spun it on the end of a drill and cord to separate the contents, measured and analyzed the proportions and then went back to the dealer for one of the sand grades.

He took me in the back room to load and I saw other components stocked in bulk that were the other ingredients so I got the right proportions of that also. I left out the blue powder dye

(aha... the mystery secret) and he realized I knew the formula and asked If I wanted the blue also. We smiled at each other.

Good luck, run small tests first of course so you don't loose any great works but that is the game and when successful you will save a bundle of money of the commercial media.


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