Cold casting (also called bonded metal) is a casting process for making models, statues, and other sorts of casts with the appearance of metal. Unlike other casting processes (such as lost wax), cold casting doesn't involve the high temperatures required to melt metal. Instead, powdered metal is mixed with urethane casting resin. The resin is poured into a mold where it hardens and bonds the powdered metal together. The object can then be polished, buffed, or have a patina applied.

When used to create bronze statues and casts, this process is called bonded bronze.

It may take a few experiments and tries before you have success with cold casting. To get started, I'd recommend first trying to make a urethane cast without the metal powder. Make a mold of what you'd like to cast with Smooth-On Smooth-Sil 901, which is easy to work with.

For pouring into the mold, Smooth-On Smooth-Cast 300 or Smooth-Cast 325 Colormatch are good urethane resins to start with. The Smooth-Cast 300 may be easier to find in stores and cures to white. The Smooth-Cast 325 Colormatch is a color-neutral clear amber so works better for cold casting. To use these, mix the resin and hardener 1A:1B by volume and then pour them into the mold. Without any additives, this will give you a paintable and sandable surface. If you want to cold-cast, mix the powdered metal into the B part before mixing in the A part. You may also wish to add a small amount of coloring to give more depth. You'll want to experiment with ratios, but it will probably end up being something like 1 part A to 1 part B to 9 parts of powdered metal, by volume.

All of these (the powdered metal and the Smooth-On products) should be available or orderable by your local craft store.

Be sure to follow appropriate safety precautions (such as eye protection, hand protection, long-sleeve clothing, and good ventilation) while working with these products. Read the material-safety data sheets before beginning to work with them! When working with powdered metal, you should be aware that some powdered metals are highly flammable/explosive, and are also probably not things you want in your lungs.

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