Re: Metal Casting Plaster

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Posted by bruce paul fink on September 14, 1999 at 05:16:53:

In Reply to: Metal Casting Plaster posted by Mark on September 13, 1999 at 23:35:59:

Thanks Mark for the find:

I love the listed company description of the very detailed controls and superiority of their product as well as the further disclaimers of what might be wrong if it does not work right.

I first heard of this many years ago but it was not on the market yet in my area so never tested their specific product.

It is my guess that this metal casting product fits the very description of everything we tried but found too exacting for our use due to the differences required in each separate size casting. It may work very well if you do a fairly set sized and limited mix so all the many controlled temperatures /water /mix / mixer motor speed and HP /paddle /timings /rate of pours /and clean container configurations can be kept to a formula pattern. These were just too exacting for me to consistently follow in my studio.

.

I will be looking forward to your further info but in the meantime I believe this is the old standard / laboratory /

research paper controlled plaster and sand and detergent product.

It explains the reasons for the need for exact water / plaster proportions, temperature controls, for the soak and time maximum mix settings and the rate of continuous pour into the mold.

It also explains the need for the controlled burnout of the pieces and the temperatures they suggest.

*** Note that unlike sand and Petrobond you still need to do a burnout even if the matchplate mold is without wax or other... all plaster based molds need that burnout for chemical moisture content even if you have sun baked out the mechanical water.

What I came up with back then was simply a standard plaster / and fine sand mix (50 : 50) and the addition of a detergent so the mix would foam in the process and form a volume about double the original start quantity. The pour had to be done immediately and the setting of it follows very fast before the mix can settle or separate into sand and air bubble levels. This was too critical for my use and able to become one uncontrolled variable too many.

Another problem I had was due to the sizes of mold pours needing more than one mix / pour per unit. Successive pours do not work well as each forms a natural separation line (often with disproportionate fine air bubbles on that line).

If you stick to a set mold / flask size though I imagine you could get great results. Basically the biggest advantage could be that the investment is more porous and assisting less air entrapment if you are doing any vacuum casting or needing more finer air vents than you would want to later remove and chase.

Burnout savings in fuel and time might slightly show up but only if it is a production line you could set exact adjustments to.

Pulling match plate molds could be an advantage over Petrobond due to the finer surface detailing now being that of a plaster based investment vs. a solidified sand faced investment... but we are starting to split hairs here. As far as saving any money on it cost wise??? Not in my place.

I am sure you can do a quick test of the media on your own though but do follow their very detailed guidelines for that.

When I was first experimenting with the detergents in the 60's the investment was cast into 3 inch diameter glass cylinders so I could watch the mix set up (or settle and separate before it set up.) It was the main reason I abandoned the use as mixing and pouring times had to be too fast for me to function well.

I also found that instead of mixing in air and trying to hold it in exact suspension until it set... I could control that volume and get the same effect by mixing an organic and burnoutable "other". These others were at first tried with the powdered wood dust from a belt sander bag, and then (since I ran out) just old flour which could be bought cheaper if it was rancid.

I use neither anymore as the volume needed became to involved and results were not that advantageous but it did become the cursor of the business company name I have worked under since 1974.

Thanks again Mark and we are waiting to hear of your take on this product.

signed

bpfink

designer/sculptor

President/owner of

Strawberry Shortcake Construction


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