How to Smelt or Cast Silver
Silver is a metal that has been smelted and cast from its raw ore for thousands of years by blacksmiths and other people working in a small scale, home-based environment. The process of extracting the noble metal from its raw ore is time consuming and difficult but as a unique hobby it can be done in a home workshop with some simple tools.
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Things You'll Need
- Crucible
- Silver ore
- Furnace
- Borax
- Flour
- Hammer
- Ceramic mold
- Blacksmiths tongs
- Cupels
Instructions
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Find a large quantity of silver rich ore. The amounts of silver usually encountered in ore are very small, anywhere from 1 part per hundred thousand to 1 per million units of volume (grams, pounds, etc.), so you'll need a large quantity of ore or a smaller sample of extremely rich ore. Crush the ore down to a fine powder if possible or at least crush it to the consistency of course sand.
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Wash your crushed ore thoroughly in a bath of water. Keep washing the ore until the water is clear. This will dissolve and clean away undesirable salts and clays naturally found in many ores, all of which can interfere with smelting.
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3
Place your crushed ore in a crucible, which is a heat proof container for use in furnaces. Add a flux agent to the ore, in this case Borax will work at a quantity of 1/3 of the ores weight. The Borax lowers the melting temperature of the silver, making it easier to melt and separate from the slag. You should also add 1/3 ore weight worth of flour as a source of carbon, which prevents oxidization of the silver as it's extracted. Aside from these you should also add twice the weight of the ore in a material known as litharge, which will turn into lead in the heat of the furnace.
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Place your crucible in a heated furnace. The furnace should burn to at least 1450 degrees Celsius and as high as 2000 degrees if possible. As your ore mix burns, the litharge you added will convert into liquid lead and the lead will trickle down through the crushed ore and strip it of its noble metals, in this case silver and the trace amounts of gold which are usually found in natural silver. The heavy lead/silver mix will collect at the bottom of the crucible while the lighter slag materials pool at the top.
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Remove the crucible from the furnace with a long pair of metal tongs and pour out its contents into a mold made out of ceramic or some other extremely heat resistant material. The lighter slag, which is floating at the top of the crucible, will pour into the bottom of the mold, and the lead/silver to the top. Allow the substance to cool. You should now have a layered "cake" of slag at the bottom and silver/lead on top. Separate the slag from the lead/silver with a hammer.
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Place your chunk of silver/lead fusion in a type of container known as a cupel. These are specially made out of certain kinds of compacted ash that has been mixed with water and are sold by assay labs. Place the cupel containing your lead/silver into the furnace again but at a much lower temperature of 850 to 900 degrees Celsius and bake it until the lead has liquefied into the litharge it started out as and has been absorbed by the cupel container. Once this is done, remove the cupel from the furnace. What remains will be a pellet of pure silver with trace amounts of gold in it
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Tips & Warnings
When separating the silver from the lead in the furnace, absolutely make sure that you have a high quality ventilation system in place. Lead fumes escape during the process. These fumes are extremely toxic and corrosive.
References
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