Casting

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Casting Pewter

One of the more common activities of a pewtersmith is casting pewter. This is the process whereby pewter is heated until it becomes a liquid, and is then poured into a mold. It is then allowed to cool, hardening again into a solid. The cooling pewter takes on a new and desired shape. Jewelry, handles for hollowware, animal miniatures, and various collectibles are examples of pewter items that are cast.
Pewter is heated in a white metal furnace. (See photo, left.) It is basically a cast iron pot, fired with LP or natural gas, and thermostatically controlled to maintain desired and consistent casting temperatures.
Pewter becomes paste at approximately 350° F. and melts to a bright, silvery, free-flowing liquid at about 380° F. Depending on the size and shape of the item being cast, the pewter is ladled into molds at temperatures between 500° - 800° F. The larger the casting, the cooler the liquid pewter is poured into the mold. (Larger masses of pewter cool more slowly than smaller ones.)

A common method for casting jewelry and other small items in pewter is to use the process of centrifugal rubber mold casting. Here the pewter is poured into a flat, two-piece rubber mold while it is spinning in a casting machine. (photo left.)
An opening in the center of the top section of the mold (photo, right.) allows the pewter to flow into the cavities of the mold while it is turning in the casting machine. The centrifugal force presses the liquid pewter throughout the mold in the seconds before cooling, and returning to it's natural, solid state in the mold cavity. Molds are made of vulcanized or cured rubber, similar to that of an automobile tire. Molds can be designed to cast multiple items at the same time, or as production molds so that many like pieces are cast on the same pour.

Another method of casting pewter is known as "slush" casting. This process uses a mold made of bronze. The bronze mold allows the pewter to flow into the mold and is poured out again before cooling and completely hardening. Pewter takes on the shape of the mold and remains hollow at the same time. The liquid pewter cools faster closest to the bronze, allowing the center to be poured back out, leaving the inside hollow. Tankard handles that are large need to be hollow so that they do not make the piece top heavy or tip to one side. A bud vase that is slush cast is another example of when the hollow casting is deliberate and comes in very handy.
Temporary molds, or molds that do not need to be used again after having been cast once, are made of various silicones that start out as a liquid and harden over night around a model or design. Once hardened, the silicone can then act as a mold for the pewtersmith to pour melted pewter into.
Busy pewter workshops will collect a great number of rubber molds over time. Rubber molds are generally stored in large steel racks, (left,) and under benches, (right,) or stacked on the floor wherever there's free space for them to accumulate.
Once the pewter is cast, it is allowed to cool until the pewtersmith can remove it safely from the mold without being burned. The piece is then worked by hand removing all flashing excess metal around mold seams by scraping, filing, or sanding. The pewter is then polished to its finished sheen with either a glossy or satin luster, proudly showing it's natural splendor and beauty.

Please e-mail any questions about casting pewter. send e-mail TOP