If you are looking to cast pewter, the following method works.
Raw material: Buy up some old pewter tankards from charity shops. Hacksaw off the rim, base and handle. Hacksaw down the length and open the body up to a large flat piece. Use metal shears and cut it all into narrow strips then cut these into small chips. They will melt easier of they are cut into small pieces. Chop up the base, rim and handle as well and add it to the pile.
Mould: Plaster of paris works, but (Gyproc) Hardwall plaster works better. You can buy it from B&Q and it is the kind of plaster that they use in hospitals or anywhere trollys are likely to bash against the wall. it sets really hard and your moulds will last for ages.
To make the mould: For example if you want to make a pewter pendant, and your master pendant is a plastic pendant from a tourist shop, you can do the following (you only have to do this once). Lay the master on a bench. Lightly spray with dilute fairy liquid. Press soft clay or plasticine firmly onto the master. Turn it over and carefully remove the master from the clay. The fairy liquid should help it slip out easily.
Next, melt some wax - ordinary candle wax will do. Place the clay in a dish and carefully pour the melted wax into the void left by the master. Let it set. Once set you can peel off the clay and clean up the new wax master.
Take a couple of small boxes (the insides of match boxes work well for small castings). Mix up some plaster, place the wax master face up in the bottom of one of the boxes and dribble plaster over it carefully ensuring no air bubbles remain. Continue until the box is full. Let the plaster set. (I am assuming that the back of the pendant will be plain in this example). Fill the other box with plaster as well.
Once both boxes have set and hardened, tear the boxes off and you'll have two plaster moulds, a front and a back. Hold them face down on a sheet of fine sand paper and abraid them back and forth until both surfaces are perfectly smooth. Heat the front part up (pop it in the oven for a while, face down on a dish) so the wax melts out completely.
Once the wax has gone, carve a narrow tube from the top of the mould to the casting part and open out the top of the tube into a funnel shape. Do the same on the back of the mould making sure they match up when both pieces are held in register.
Place both moulds in register and wrap together with a piece of wire so they are secure.
Take a tray and place a 2" layer of sand in it. This is where you will do your casting.
Using a heat source (gas camping stove) melt a small amount of pewter chips in an old ladle. If you have a gas blowlamp you can play the flame on top of the ladle to sped up the melting. Once you have molten pewter, pour it into the funnel in the mould. make an indent in the sand beforehand and pour any excess pewter into the indent so it'll harden and you can use it again. Don't leave any pewter in the ladle to harden.
Allow the casting time to harden then remove the wire and crack it open. You should be able to lever out the casting using the funnel of pewter. Check it for detail and if you're happy with it, snip off the funnel and tidy where you snipped it with some wet and dry or a fine file.
If it doesn't workout like you expected, try and figure out why. If it's a big casting, and it is only partly filled, you may need to make a vent hole next to the filling hole so air can escape allowing the casting to fill properly.
Once you master this technique, you can progress to making moulds with multiple castings.
Always do you castings over a bed of sand. Always wear goggles, a leather apron and leather gloves. Always make sure the casting is cool before being tempted to open it.
Hope this is helpful,
Eric
