The foundry is built using furnace repair bricks for the refractory. The bricks are extremely lightweight and can be cut like foam using hand tools. No casting forms, tamping, or mixing are needed. The furnace bricks hold heat very well, allowing fast melts with low flame settings.
Here is the refractory brick furnace side view. The frame is made from regular galvanized angle iron and threaded rod. The foundry takes up to a #3 graphite crucible. The entire foundry is a single unit, sturdy, and easily carried by one person.
The brickwork is held together by tension of the threaded rods through the galvanized angle pieces. No mortar or joint compound is used. Four short lengths of angle iron are placed on the refractory's corners to spread the clamping force evenly.
The chamber is made from four bricks, cut to a square "C" shape. The shape was roughed out using a bare hacksaw blade, and then finished to shape with a wood rasp. Two uncut bricks form the bottom of the foundry. The hinged lid is made from two bricks held in an angle-iron frame. The hinges are adjustable by shimming with washers so the lid fits flush with the top of the chamber.
The blower is an old Dayton blower picked up at a flea market. The burner consists of a length of 1" iron pipe with a quarter-inch propane gas line centered in the pipe. A regular compressed-air quick coupling attaches the low-pressure propane gas hose to the burner feed line. A standard fixed-pressure propane regulator is used on the tank, with a quarter-turn gas valve connected between the regulator and the propane hose. A regular light switch controls the blower.
The bricks are Replacement Furnace Bricks, catalog number 160-916, sold by Swest Inc.. McMaster-Carr lists similar bricks on their online catalog, page 3235, catalog number 9355K1 and 9355K2, but for a much higher price.