MEDALLION AND PLAIN CASTING
Fig. 13. Fig. 14. Fig. 15. Fig. 16. Fig. 17.
Coin and Metal Casts
This same procedure may be employed when making moulds and casts from coins, medals, and medallions. A narrow frame is made of wood, and at the middle of this a medal is placed on the flat oiled surface of a board, a slate, or a piece of marble, as shown at Fig. 14. The face of the object is now prepared with the oil, and the plaster is poured as previously described. If any number of reproductions are to be cast from the mould, it would be well to give it one or two coats of thin shellac; then oil it before each impression is made.
Plaster-casting in General
It is not a difficult matter to reproduce in plaster almost any object that has no undercut or parts that will not easily detach from a mould. When making them, the first thing to do is to get a piece of board about a foot square; that is to work on, so as not to soil the table. Then you want a lump of clay about as big as a football, five or six pounds of plaster of Paris—it only costs three cents a pound—and a half-dozen wooden pegs. You also want a cup of warm melted lard, or Castile soap dissolved in hot water, to rub over what you are going to copy, so as to prevent the plaster sticking to it.
Now, suppose it is an egg you want to copy. You rub it all over with your melted lard, and lay it down on the piece of board. Pack clay around it as high up as the middle of the egg, and as far out as half an inch from the widest part. You must be particular about not putting clay higher than the middle, because, if you get the clay too high, you can’t get the egg out without breaking the mould.
When you have the clay around the lower half of the model, smooth and level it, and push two pegs in opposite corners, as shown in Fig. 15. Now around the whole thing make a box or case of clay, with sides rising half an inch higher than the model (Fig. 16). Mix plaster of Paris and water together till you have it like molasses on a warm day; pour that into the clay box, so that the model is covered, and the mixture even with the top of the box.