In the case of my Perky’s Paw charm, I created between 40 and 50 models to get it just the way I liked. To repeat this process for each necklace would not only make me crazy, but would be prohibitively expensive. Casting was my solution.
Casting is the process where a model is used to make a mold from which many identical pieces may be produced. Technically they should be “identical,” but in reality each charm is hand cast, then individually finished by me – so more similar than identical.
The casting company I was lucky enough to find is Frank Billanti Casting Co., Inc. Frank has been in the casting business for over 35 years and last year opened his own facility, with state-of-the-art equipment. It is a family-run business – Frank, his wife Kathy and their daughter Kristin are wonderful to do business with. The Perky’s Paw charm was my first experience in having a model cast and they were quite helpful with advice and explanation of the process. Casting for a jewelry-scale project was quite different from the casting I was familiar with as a metallurgical engineer.
First, a mold was made of my Perky’s Paw model. I opted for the dimensionally more stable silicone mold over a rubber mold. The silicone mold is then injected with wax to make exact replicas of the original model.
A wax sprue is added to each wax mold – the sprue is a small funnel shaped piece through which the molten silver will flow. These small wax replicas are then connected to a wax “tree,” through which the silver will run and fill all the mold
The wax mold is then coated with a plaster slurry. The plaster is dried in an oven and the wax is burned out of the plaster mold, leaving a cavity the exact shape of the original model. The sterling silver is melted in an induction heater and the molten silver is poured into the plaster “tree,” under vacuum, to minimize bubble formation.
Well, it’s a little more complicated than that – attention must be paid to the mold making, sprue placement, wax forms and so many other things – but these are the basics of the casting process.
Down the road I hope to get some photos of what the molds look like after each step – hey, you never know, someone out there might be interested!