Fig. E: Bend the element wire into shape, forming a loop
that passes through as much of the object as possible.
Fig. F: Push the molten plastic into the mold, then lay
the element wire over the top of 1 half of the mold.
Fig. G: The finished molding will have excess bits
attached. Fig. H: Clean off the excess with a sharp knife.
3. MIX PLASTIC COMPOSITE. over the top of 1 half of the object (Figure F). The
Friendly Plastic is a low-temperature, moldable ends of the wire should stick out from the end of the
plastic called polycaprolactone (PCL). At higher object, so that they can be connected to the rest of
temperatures, PCL becomes sticky (like a hot glue), the electronic components.
and it can be mixed with various additives to alter Remelt the plastic in the mold with a heat gun,
its physical properties. and then quickly bring the 2 halves of the mold
To make the composite, simply melt some together. The 2 plastic pieces should bond together,
Friendly Plastic in a pot over low heat until it’s easily trapping the element wire between them. Let the
stirred but not so hot that it smokes. Then switch off mold cool for about a half hour, and then open it.
the flame and add the aluminum powder, at a ratio You may find that you need to smash the mold to
of about 2 parts plastic to 1 part aluminum. The get at the object. This usually happens if you stuffed
aluminum will help transmit heat evenly through the too much plastic into the mold, or didn’t use any
plastic, accelerating the remelting process. Mix the mold release.
composite until you get a smooth, gray emulsion. The finished molding will probably have excess
plastic and bits of the mold clinging to it (Figure G).
CAUTION: Be very careful with the plastic in its Clean these off with a sharp knife, and smooth any molten state — when overheated, it behaves a bit like boiling sugar, and it will stick to your skin, leaving a rough edges with a hot blade (Figure H). Be careful
painful burn. Because you’re melting the plastic over a at this stage, since the plastic composite will melt
direct heat source rather than with hot water, you should very quickly if you apply too much heat.
always handle it with a spatula and not with your hands.
4. CAST YOUR OBJECT.
Use a spatula to push the molten plastic into the
2 halves of the mold and then lay the element wire
5. ATTACH THE BATTERY
Next, you need to connect your battery to a reed
switch. The easiest way to do this is to strip the plas-
78 Make: Volume 16