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How to Cast Silver Bars

Silver bars or ingots are cast from solid sterling silver that is 92.5 percent silver and the rest copper, zinc or other trace metals, or fine silver that is 99.9 percent silver. Typically, small silver bars obtained from mints or silver dealers cost more than larger bars available directly from a foundry. Bars are made in sizes of 500 grams, 1,000 grams or one kilogram, 1 ounce, 2 ounces, 5 ounces, 10 ounces, 50 ounces, 100 ounces and 1,000 ounces. The smaller sizes are practical when you want to liquidate only a small amount of silver; the larger bars provide a longer investment vehicle. Silver bars are cast in one of three ways.

Things You'll Need

Sterling silver or fine silver
Closed or grated molds
Metal file
Open mold
Induction oven or induction coil
Carrying crucible
Vacuum pressure casting machine

Instructions

Closed Casting
- 1
  Liquefy the silver by heating it in an induction oven or by using an induction coil.
- 2
  Feed the molten silver into the closed mold using a gating system that will then be closed to allow the silver to cool and harden. A water bath can be used to accelerate the hardening.
- 3
  Open the mold and inspect the bar.
- 4
  File down sharp edges and the raised surface, or sprue, at one end that is part of the gating system that fed the molten silver into the bar. The completed bar should be smooth and safe to handle and stack.
Open Casting
- 5
  Liquefy the silver as in Section 1, Step 1 above in a carrying crucible.
- 6
  Heat the mold in an induction furnace.
- 7
  Pour the molten silver from the carrying crucible into the open mold.
- 8
  Place a cover over the mold to reduce silver shrinkage and oxygen absorption from the air.
- 9
  Allow the silver to cool without moving the mold or adding cooling water. This will produce a smooth top surface.
Vacuum Pressure Casting
- 10
  Melt the silver in a graphite crucible heated by an induction coil.
- 11
  Place the mold in the lower chamber of a vacuum pressure casting machine, allowing the mold to heat.
- 12
  Activate the casting sequence once the silver in the upper chamber is liquefied. The casting chamber is flushed with helium, and all air is removed from the lower chamber.
- 13
  Preset the valve opening and closing times according to the machine's specifications. The upper valve will open and close automatically, allowing the molten silver to flow into the mold below.
- 14
  Open the chamber once the vacuum pressure casting machine indicates that the vacuum has been released. Remove the cast bar and quench it in water to speed bar solidification.

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