I have a few projects in mind that involve lost wax casting, the problem is that the greens sand casting that I’ve tried before just doesn’t have enough detail for what I have in mind. Does anyone know where i could buy some investment plaster to get a higher level of detail?
We have have 3 different kinds of specialty investments, plus some old fashion plaster Paris. Specifically DMS has on hand…
- Ultravest
- Plasticast
- Solitaire
You find specific information on each of those here… https://www.ransom-randolph.com/investments
Hope this helps.
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will regular plaster-of-paris still work for casting metals like aluminium, brass, and pewter? I was under the impression that it would put off gas when it came into contact with hot metals, ruining the fine details of the casting. Did Youtube lie to me?
The main thing with PoP is used for metal casting is to make sure it is VERY dry or it may explode from the steam
is there a way to ensure that it is dry beyond just letting it cure for a day or two? Microwave it? Put it in a kiln? Hit it with a heat gun?
Many many many moons ago … I put mine in the oven at about 250F for an hour or so.
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Or a car in the Texas heat.
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be sure to crack the window to let the steam out.
Plaster of Paris will handle heat up to around 1400F, I’ve been told. It takes time for it to break down at that temperature, so the gases produced from pouring molten metal into it, such at the 2000F bronze we use for jewelry, for example, isn’t much of a problem. Jewelry investment has things added to it to let it release some gas through the natural pores in the investment.
I’ve used plaster of Paris mixed with up to 50% fine sand and still had pretty good detail, so if you’re home casting you can try that, help the heat factor a little, and save some money on the amount of plaster. I did say “fine” sand. You might run it through a screen to take out large particles if you are using play sand or something similar. You can get finer sand at sand blasting supply houses or sometimes sold as aquarium sand.
As above, make sure the plaster or investment is perfectly dry by first letting it dry naturally for several hours, then baking it in an oven. In jewelry we put it into the kiln and raise the temperature to 1350F, which sinters the investment and weakens it enough so that it crumbles when we dunk it in water. Then we lower the temperature to about 1000F for the metal pour so that the metal going in won’t go solid before it has a chance to fill the mold. Plunging it into water after the metal is solid lets the steam pummel the investment to soft mud and the mold comes right out.
Warning! If you cool the plaster/investment after it’s dried it will absorb moisture from the air and you’ll need to put it back in the oven again before pouring molten metal into it. The slightest bit of water inside can cause molten metal to be forced out and splash. Wear cotton or leather when you do it. Wear full shoes or boots.
PS. Oh, and in answer to your question about WHERE to get investment, Roseco jewelry supply or Rio Grande jewelry supply online.
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would the plaster/sand mix have enough detail to hold numbers on a 20 sided dice?
It should (note the italics). The depression on the die face isn’t very deep and you’d have to make sure the plaster and sand got all the way into the number depression without having any air bubbles or anything trapped under it. Some people will put the first layer of plaster very thin with a brush and others will splash plaster onto the surface by touching a brush into plaster and flicking it so the plaster flies off onto the surface. In jewelry we use a vacuum chamber to expand and pop all the bubbles. With some care it is certainly capable of catching all the detail. I’ve had castings that I could see my fingerprints on the surface or wood grain of a carved original.
i might try doing both methods. i know that creative arts has a vacuum pump, and i can set up a decent vacuum chamber with an old pot, a piece of clear acrylic and some hose hardware