| 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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