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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?

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  • I thought that people usually use plaster with metals.
    – EmRoBeau
    Oct 29, 2018 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, 2018 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, 2018 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, 2018 at 19:41
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    What exactly do you want to make? Which metals are you thinking of using? The type of material to use for the mould depends on both the metal you wish to cast and the size of the casting, as well as the amout of surface detail and the surface finish you want. And a few other things too. There is no silver bullet or "one-size-fits-all" solution.
    – Gwyn
    Nov 12, 2020 at 1:51

4 Answers 4

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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.

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  • "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, 2018 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, 2018 at 16:03
  • Not really. The foundry I worked in used mostly solid polystyrene and some wax for larger parts and short runs ( not many) parts . Never saw foam patterns, I expect they would produce a rough surface . Not to split hairs ,but we poured both investment molds and shell cast .
    – blacksmith37
    Oct 17, 2020 at 21:22
  • @blacksmith37 Yep, that's "lost foam" casting; polystyrene is foam. The surface depends on the surface of the foam piece, with smoother starting pieces giving smoother results. My experience was art-based casting, with an instructor who adapted industrial polystyrene casting to artistic purposes in our foundry.
    – Allison C
    Oct 19, 2020 at 0:12
  • Foam is foam ,solid is solid , polystyrene can be either.
    – blacksmith37
    Oct 19, 2020 at 1:55
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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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I have not done this myself, but you can use laser cut/etched MDF as molds for pewter.

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  • The original question could use some clarification. Most readers interpreted it to mean that the OP is looking for a general purpose mold material that can be used with any common casting metal (and the OP's response seems consistent with that). However, it could also be interpreted to mean that the OP wants to cast something from molten metal, and the metal and its characteristics aren't important or are unspecified. In that case, there are some metals that melt at a low enough temperature to use cardboard molds, and amalgams that can be molded at room temperature. (cont'd)
    – fixer1234
    Oct 18, 2020 at 18:27
  • Answering that interpretation would benefit from more criteria from the OP to avoid a potentially endless collection of specific examples that may not be relevant to the OP's unspecified needs. BTW, welcome to Arts & Crafts.
    – fixer1234
    Oct 18, 2020 at 18:28
  • True, I interpreted 'any' as 'some' rather than 'every', which may not be what the OP meant.
    – tgdavies
    Oct 18, 2020 at 22:00
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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, 2018 at 20:03
  • I wouldn't call it "plaster or clay" after vitrification in a kiln.
    – blacksmith37
    Oct 30, 2018 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, 2018 at 15:54
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    Be careful not to interpret the downvote on Blacksmith37's answer as meaning that it is safe to pour into a damp mold. A mold must be fully dry before pouring in molten metal, or the water vapor caused by the molten metal hitting the damp mold will blow the metal back out, and possibly also blow the mold apart. I have pewter splatters on my ceiling to remind me of this. Fortunately no accidents with silver or bronze yet.
    – fwkb
    Nov 18, 2020 at 23:23
  • Not only damp but also water of hydration. Real foundry sands are compounded to give porosity for steam to escape.
    – blacksmith37
    Nov 20, 2020 at 19:42

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