Having a backup casting of your key can save you from locking yourself out of your home or car. Make a duplicate key without a locksmith by casting a copy with clay moulding materials. It is cheap to copy any key with the right craft products. The process can be completed in under an hour. Copies are typically made with alloy slug, a cheap metal that dries and melts quickly.
Cut the brick of craft clay in half with a knife. You want both halves to be about equal. You should cut the clay in half along the length.
Exert pressure on the clay with your hands to warm it up. This is done by gently kneading the clay. Do not twist or break the clay.
Press the clay into the key casting mould. You will press the clay into the half that has two vertical pins. Press the clay until it is even with the surface of the mould. If there is excess, cut it off with the knife. Run a credit card over the surface to ensure the clay is completely flat against the surface of the mould.
Repeat step 3 on the other half of the key casting mould.
Dust the surface of both moulds with talc powder. Blow off the powder that does not stick to the clay.
Set the mould half with the pins on a flat surface, with the pins facing up. Press the key into the clay. Press the other half of the mould on top of the key and properly align the vertical pins in the appropriate holes.
Place a heavy weight on the mould for about twenty seconds. For a weight, you can use a fifty-pound lifting weight or you can simply stand on the mould. Pull the mould apart and remove the key.
Bind the mould together with two strong rubber bands.
Melt alloy slug in a ladle by holding it over a medium flame. After the metal has melted, leave the ladle over the flame for an additional thirty seconds. Warm the inside of the mould by holding it for five seconds over the flame.
Pour the casting into the mould. Tap the mould on the table a few times to make sure the metal covers all the small nooks. Wait thirty minutes for the cast to solidify.
Hold the mould vertically and pull the halves apart slowly. Lay both halves on a flat surface with the clay side facing up.
Insert a credit card under the casting and gently pry it loose.
Be careful not to accidentally pour the metal on your hands. Use gloves to protect your skin from the toxic materials.