Mould making for pewter
Casting pewter can be a fun and rewarding hobby. Pewter can be made into any number of items, from coins and medallions, to jewellery and buttons. In fact, pewter can be made into any metal item, provided that it is not exposed to temperatures above 226 degrees C (440 degrees F).
All you need is a mould to cast pewter.
A carved mould can be made from cuttlefish stone, plaster or soapstone. Softer moulds, such as plaster will survive a few castings before disintegrating. Harder moulds such as soapstone survive more castings. To create these moulds, you will need carving tools as well as your mould. A two-sided casting needs a mould for each side to fit together, while a single-sided mould can use a block of wood or other hard surface for the back. Select your design and carve it into the face of the mould. The design should be in reverse to your desired finished design. The areas you want to be in largest relief in your finished design should be carved deepest into the mould. Do not make any undercuts, as this destroys the mould when you attempt to remove the cast pewter design. Then carve your sprue and air vents. The sprue is the funnel-shape into which you pour the molten pewter. If your mould is two-sided, carve alignment pegs into the mould.
A pressed mould is one in which you sculpt your design out of clay or wood and then cast it into the mould. Examples of pressed moulds include sand casting moulds, clay moulds and moulds made of RTV, urethane or silicone. For this type of moulding, start with a model. You can form your model out of hardened clay such as sculpey or a carved design such as the type carved from balsa wood or cork. Press this into your moulding medium. For sand carving, make your mould out of damp sand. Clay moulds will have clay that is pressed into a square frame. RTV comes in two parts, putty and a silicone. The putty and silicone are mixed. Then the mould is pressed into the resulting lump of goo. When the goo hardens, it forms a rubber texture that can be peeled away from the mould. For sand casting, the molten pewter is poured directly into the sand, or into two blocks of wet sand that have been joined to form a front and back side. Clay and RTV moulds may be backed with the other side of the mould, or with a flat structure such as a board. In these instances, a sprue, air vents and alignment pegs will also be required.