Shape a positive from wax. Use fine sculpting tools to create a wax version of the finished sculpture. Warm the wax slightly to make sculpting easier, but be careful not to soften the wax too much. You don't want it to become misshapen as you work.
Attach vents and and gates to the finished positive. Heat the tip of a metal tool over a flame and use the hot tool to fuse one side of the thin wax rods (the vents) to a funnel, and the other side to the top of your wax sculpture. These will provide escape passages for gas during the pouring process. Attach thicker wax rods (the gates) to the bottom of the sculpture, where the bronze will enter.
Contemporary sculptors often make a silicone mold into which they pour hot wax to create a positive. If you are making an edition of sculptures, making a silicone mold will allow you to recreate the same sculpture over and over again.
Cover the finished wax figure with liquid clay. This process, which is called investing, entails dipping the wax figure into a clay slurry and then dipping it in a sand bath about nine times. When fired in a kiln, the wax melts away an leaves behind a thin but sturdy ceramic shell.
This step illustrates why this casting method is referred to as "lost wax." The wax leaves the ceramic mold, which creates a negative imprint for molten bronze to fill.
Pour bronze into your ceramic mold. Melt bronze in a crucible at 1,700 degrees Fahrenheit in a gas furnace, and immediately pour into a room-temperature ceramic mold. You will need to lift the crucible out of the furnace and pour quickly and precisely.
Break the bronze out of the ceramic mold. You can often easily crack off chunks of the mold, or you can sandblast stubborn areas.
Remove bronze vents and gates with a hack saw, and remove any imperfections with a Dremel tool or a sandblaster.