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I have found that for one to create a mold for pouring molten plastic in it, it only requires clay.

But what about metals? Are there easy materials to find so that I can use them to assemble them and create a mold for pouring any molten metal for giving a shape to it?

  • I thought that people usually use plaster with metals. – EmRoBeau Oct 29 '18 at 17:09
  • @EmRoBeau Really? I don’t think that’s correct. Because the molten metal, can cause serious problems while pouring into a plaster. – Alex A Oct 29 '18 at 19:09
  • @AlexA I've used plaster for silver (both fine and sterling), ceramic for bronze, sand for iron, and selastic rubber for pewter. There's no issues with pouring metal into plaster, what issues do you think there are? – Allison C Oct 29 '18 at 19:33
  • @AllisonC I was thinking that, perhaps when you pour molten metal into something, then that something can melt and cause serious problems. And I was thinking, that it needs something hard, powerful enough that can guarantee security and protection. – Alex A Oct 29 '18 at 19:41
  • @AlexA Plaster does not melt; nor does ceramic, and sand is fine at the temperatures used for cast iron. Similarly, selastic is temperature resistant to a certain level, and pewter melts at a comparatively low temperature, so it won't melt in that case. – Allison C Oct 29 '18 at 19:45
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For use with the widest range of metals, a properly prepared ceramic mold is your best bet. It can tolerate high temperatures and capture fine details well. However, these are commonly single-use molds that are broken to remove the cast object.

Rather than trying to find a "silver bullet," you're better off targeting your specific needs for each case. If you're casting a single sculpture in bronze or aluminum from a wax base ("lost wax" casting), use the ceramic mold. If you're doing a styrofoam master sculpt to cast ("lost foam" casting), use sand. For precious metals, use kiln-dried plaster. For low-temperature metals in one-off casts, plaster works well; for multiple casts, a heat-resistant rubber or some metals will work better.

  • "Lost Wax" ( polystyrene for parts made in quantity) typically uses hydrolyzed ethyl silicate and silica sand for mold materials , but I thought that was beyond the scope of the question. – blacksmith37 Oct 30 '18 at 15:57
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    @blacksmith37 I think you're speaking of what I described as "lost foam" casting, which does use those materials, but I didn't do it as frequently and similarly felt it was a bit beyond the scope of the question, particularly as the OP seems to have no metalwork experience at all. "Lost Wax" uses wax and a ceramic slip mold (with sanding between layers after a base has been created) which is burned clean before casting. – Allison C Oct 30 '18 at 16:03
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Traditionally cast iron was cast in sand, link to a Wikipedia page about casting in sand.

And I have also seen other metals cast in sand, like pewter and silver.

And as indicated in the comments on the question, other materials can be used as well. Like plaster, ceramic, and even some kind of rubber for pewter.

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The first problem is water/ steam. If you pour 600 F solder or zinc into a plaster or clay mold it will make steam which will spoil the casting. Keep in mind materials like plaster of paris have water of hydration which can be released although they look dry. A mold made of metal works for low temperature metals . To cast higher temperature metals like copper base and aluminum you would best use foundry materials for a mold , essentially sand with some binding agent. I don't think anything can be made without problems.

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    Plaster and Clay (ceramic) are both commonly used as casting mold media. Both are kiln-dried to prevent issues with steam, and are used for high-temperature media (silver and bronze both melt at ~1800 F; silver is commonly cast in plaster, and bronze in ceramic molds). – Allison C Oct 29 '18 at 20:03
  • I wouldn't call it "plaster or clay" after vitrification in a kiln. – blacksmith37 Oct 30 '18 at 15:49
  • Plaster is still called plaster even after kiln-hardening. Clay is still called clay after kiln-hardening. Sorry, but the answer is still incorrect. These are materials that are specifically used in casting high-temperature materials. I have used both extensively in both foundry and jeweler's settings in the past. – Allison C Oct 30 '18 at 15:54

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