Casting molten metals?

What mold materials are suggested for making cast duplicates of metal objects Metals that may be used in some of my planned projects may include aluminum, brass, bronze, mild steel, and the like. (Jewelry, belt buckles, as well as similar items are planed)

I realize that the high temperature may be a problem in material choice for the molding material(s). I think mild steel is the highest melting temperature of all the metals I've considered, and it's about 2700°F (1482°C). (Suggestions for easier to work with metals or hard casting materials would be happily accepted, considering I'm looking to make a set of reusable hard positives to make casting negatives for larger numbers of final product.)

The choices I make for FINAL material will also include how well they can be plated, so steel may be for an intermediate mold positive, and something more easily plated (with yellow gold) like brass would be a final choice. Though, I may go for highly polishing the brass and then covering it with a corrosion inhibitor to avoid the high cost of gold.

Paige Russell8 months ago

HI John,


I'm afraid aluminum, silver, and copper have melting temperatures that are too high for silicone molds to withstand.

There are several types of RTV silicone rubber that you can use for casting low-temperature metal/alloys like tin and pewter (SmoothOn's Mold Max 60 has the highest heat resistance that I know of at 560° F / 294° C), but RTV silicone is NOT recommended for higher melting temperature metals.

To cast silver or copper, you'll need to do lost wax casting in a plaster mold. Here are two instructables and an online example that go over the lost wax casting process:

I've never cast steel, so I'm afraid you and Google are on your own for that one. :)

Hope this was helpful!


Plaster works for aluminum lead and metal that melt at lower temps higher temps you will need to look in to sand casting or lost wax methods.

mwinegardner8 months ago

For casting metals you may want to look into the sand casting process. Its commonly used for aluminum, brass, bronze, and iron. Steel is usually investment cast, i.e. lost wax.