Picture 1: Molding

A perfect master or prototype is a must for making a rubber mold. The prototype is vulcanized in uncured rubber, which is then cut apart to create the production mold. There is normally a slight shrinkage of 3-5% from the original prototype to the wax pattern that will come out of this mold. The rubber mold will normally produce from 500 to 1000 wax patterns before showing signs of wear.

Picture 2: Wax pattern production

A wax injector is used to fill the rubber mold with wax, which is then carefully removed after hardening. After touching up the wax patterns they are attached to a 1/2-inch diameter wax rod forming what is called a tree.

Pictures 3, 4 and 5: Casting process

The wax tree is then inserted into a capped steel flask and a special type of plaster called "investment" is poured into the flask to fill it. Once the investment sets the cap is removed and the flask is placed into a burnout oven, or kiln, where the wax is melted out to leave a cavity in the investment exactly the shape of the wax tree. The flask is placed in a high tech casting machine (picture 4) and molten silver is injected into the mold cavity. After the molten silver solidifies the investment is removed using a high-pressure spray gun. We see the cleaned silver trees in picture 6.

Pictures 6: Silver trees

The individual pieces are clipped from the tree using diagonal cutters designed specially for this purpose. The remaining bit of the sprue is ground off using a cratex grinding wheel.

Picture 7: Grinding. Picture 8: Unfinished product