Things You'll Need
Refractory bricks (firesand, cement, concrete or gypsum)
Propane torch
Graphite crucible
Crucible tongs
Glove and face shield
Drill and drill bit
Gold melts at about 1,800 F, depending on the karat weight. The furnace to melt the gold is very simple but must be constructed correctly to function efficiently. Safety procedures are extensive and require special equipment. This very simple furnace can be constructed in a few minutes in a backyard. Since the temperatures are high and the materials used give off noxious gases, all furnaces must be constructed outdoors.
Step 1
Make a platform of refractory bricks three times the width of the crucible. It should be placed on concrete or stone and must be stable.
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Step 2
Drill a hole in one of the bricks slightly larger than the nozzle of the torch. Each of the four possible types of brick require a different drill bit. The easiest is gypsum which can be drilled with a hand-held screwdriver. Don't simply leave a space between the bricks for the nozzle, or hot gases will blow back past the nozzle and melt it. A canister type torch will work nicely.
Step 3
Set refractory blocks in a circle slightly wider and higher than the crucible. A smaller furnace chamber will conserve heat, but you will have to fish the crucible out of the furnace so leave room for the tongs. Set the brick with the hole for the nozzle so that the torch will blow along the side wall of the furnace chamber. The hot gases coming from the nozzle are cool in the center. If the flame is hitting the crucible directly, it will not heat efficiently. You want to force rotating air movement within the furnace chamber.
Step 4
Leave the top open.
Step 5
Place the torch into the hole in the brick before lighting it. When it is flaming well, lower the crucible with the gold and flux already mixed into the furnace chamber with the tongs. When the gold is melted, the color within the crucible is orange yellow.
Warning
Gases will be coming straight up out of the furnace. Never look down into the furnace. Using a face shield, an oven glove and a shiny piece of metal, hold the metal over the furnace and angle it so you can see down inside.
The heat of the furnace is beyond common experience. Don’t put any flammable material within three feet of the furnace.
Construct a place to put the crucible after the gold is melted. An iron pan with a layer of sand is excellent.
Keep a bucket of water handy.
Wear shoes without laces in case molten gold spills on them.
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