How to Make Molds for Lead Casting
Of all the metals, lead ranks among the easiest to cast because of its relatively low melting point of 621.5 Fahrenheit. A lead alloy is better for casting, with a melting point of 500 F. However, this is still far too hot for most silicone molds. Fortunately, there are companies that produce temperature-tolerant molding silicones. These come in kits that allow you to make your own mold by mixing liquid silicone with a catalyst. Some of these silicones only go up to 400 Fahrenheit, so check the specifications of the silicone when you shop around to make sure it can withstand the heat from molten lead alloys.
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Things You'll Need
- Newspaper
- Gloves
- Respirator
- Plastic container
- Prototype
- Mold release
- Mixing cups
- High temp RTV silicone kit
- Stirring rod
Instructions
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Put down several layers of newspaper over your work area and don a pair of gloves and a respirator. Lay a plastic container on top of the newspaper.
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Place your prototype, face up, at the bottom of the plastic container. Spray the prototype and the inside of the container with mold release. Mold release keeps your mold from sticking too much to other surfaces. You can find mold release at many craft stores, but it's a good idea to use a release produced by the same company that made your silicone.
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3
Get out two mixing cups and label them A and B. Place the two bottles of fluid that come with your silicone kit next to them. These bottles of fluid are the silicone and its catalyst. Pour liquid from the two bottles into the two separate cups. Most silicone rubbers use a 1:1 ratio between the liquids, but some are different. Double check your kit's instructions find out which ratio yours uses.
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Pour the two cups into a third, larger cup and stir the contents together with a mixing rod for one full minute.
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Pour the silicone into your plastic container slowly. Pour enough to completely cover your prototype in at least an inch of liquid.
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Let the silicone cure. The time this takes depends on the type of silicone you are using, but can take anywhere from a few hours to a day. When the rubber is cured, turn the container over and tap heavily on the back of it to dislodge your mold and prototype. Remove your prototype from your mold and rinse everything with water to remove residual mold release.
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Tips & Warnings
Do not attempt casting lead without skilled supervision if you are a novice. Keep uncured silicone away from children and pets.
References
- Photo Credit lead pellet image by Evgeniy Mitroshkin from Fotolia.com
