The Making of Pewter Cabinet Hardware
Ever wonder how people make things out of pewter? Pewter is a metal alloy made up of tin, copper, antimony, bismuth and sometimes, less commonly today, lead. Copper and antimony act as hardeners while lead is common in the lower grades of pewter. The pewter that PHD uses contains no lead. The company that does our casting uses a 98% tin, 1.75% bismuth and .25% copper alloy because it gives the best finish.
The first step in production is to make a sculpt an original piece out of metal or other material. This is called the "master" or "master piece". The master is pressed into two large discs of soft rubber. The front of the master will be pressed into one disc and the back of the master will be pressed into the second disc. This can be done several times to the mold so that the mold will produce multiple pieces. The molds will then be placed into a machine called a vulcanizer which will apply pressure and heat to the molds to harden them. Channels will be then cut into the molds for the liquid metal to flow into and for air to come out. This is called gating and venting.
Once the mold is ready, it is loaded onto a spin casting machine like the one pictured above. The casting machine spins the mold very fast. Liquid pewter is then poured into the casting machine as you see above. Centrifugal force takes over and forces the liquid metal into the cavities made in the mold. You then have to wait for the metal to cool and harden. Once everything has cooled, you pull the mold out, open it up and there will be the item you are making but you are far from done.
Now you have to remove the item you want from the "flash". Flash is the extra metal formed in the channels cut into the mold that the metal flows through while in the spin casting machine. This work is all done by hand. The flash is then returned to the melting pot to be melted down and re-used in the next casting. Once the flash is removed, the piece is then inspected for any defects and cleaned so that the finish you will want will adhere to the piece.
Next blog entry will be about how the finish is applied to your hardware.