I won't tell you every single detail that's in the book, because that wouldn't be fair. The great Dave Gingery is the author that came up with the idea, and it's his idea. In addition to providing you these free instructions, I would be willing to build a foundry for you, for a reasonable price (materials plus 20 dollars labor). E-mail me with your requests, comments, questions, etc. I want to hear from you!
Ingedients:
-- charcoal
-- lighter fluid
-- 85 mesh or finer(larger #) silica sand from your local Home Depot/whatnot, (or a local foundry might give it away from their dump pile if you offer to buy it). 65 mesh will work, but makes lower quality castings.
-- fireclay, perhaps from a fireplace store, pottery place, or landscaping place. The stuff from a fireplace store may already be mixed with sand, for which you'll have to modify these instructions.
-- gallon pail, or larger container if you wish. Metal is better than plastic.
-- some sheet metal from a hardware store (called "flashing"), cut up some ducting, whatever.
Instructions:
Cut a strip of sheet metal 2" wide, and 1" longer than the diameter of the pail. Divide length of the strip by 12, and drill or punch small holes at that interval(making 11 equally spaced holes). These hole should be centered on the strip's width. Bend the strip into a circle, drill three holes where the ends come together, and put bolts(with nuts, of course) through the holes to hold the circle together. Weave some kind of wire through the holes and around a tin soup can which you center in the circle. So the wires once you're done should kind of hold the can in place. The can's going to be the furnace's vent. All the wires are just for reinforcement and durability. Now, mix 5 gallons of sand with 2-1/2 gallons fireclay. Use some of the mix to fill in the lid shape you made out of sheet metal. It should now be shaped a little like a donut. Do not let this dry before you put it in the oven. Cook at 250� until it stops steaming (2 to 3 hours), then raise the temp. to 350-400� and let cook for 5 or 6 more hours.
Cut a hole the size of a soup can in the pail, with the bottom of the hole about an inch up from the bottom of the pail. Stick a soup can in this hole. Use the same sand-clay mix to make an even wall around the inside of the pail, 1 inch thick, and also a 1 inch layer on the bottom. Don't fill in the soup can hole with lining, obviously. Ram this lining up as tight as you can, because you want it tight, not loose, without too many air-bubbles. Don't let it get dry. Now put a layer of charcoal in the pail, pour lighter fluid on, get it burning well, put in some more charcoal and wait for it to ignite well, etc., until the pail is two-thirds full. Then put on the lid, and start the air blast. It will stop steaming, then rise to a red heat. At that point cover up the vent, cut the air, cover the air blast hole, and let it cool for 3-4 hours.
Now whenever you want to make anything metal, just find some scrap aluminum or pot metal(also known as die-cast metal, it's zinc alloy) or brass or bronze. The zinc pot metal melts at the lowest tempertaure, about 800-1000 degrees Fahrenheit, aluminum at 1400 degrees, and brass and bronze at around 2400 degrees. It takes me about twenty minutes to heat aluminum to molten. Others report shorter times. Stick the metal in some kind of container that isn't going to melt--a cast iron sauce pan with handle cut off (very durable), stainless steel saucepan (good for a few melts), a malleable iron pipe cap screwed into a short pipe nipple, or an actual "official" ceramic crucible made for melting metal in. Dave Gingery does not recommend the ceramic route, becuase they're expensive and break easy. I've even used large tin soup cans, but they're a pain because they melt if there's too much metal in them, and then you have metal goo all over your charcoal. Make some sort of tongs that are going to let you pick up the pot and pour the metal without having your hands too close to the heat. Wear gloves. For the mold, you can use sand, mixed with some clay. Sprinkle flour on the surface, and then either make whatever shape you want, or press in something that you want to duplicate in metal. This is called green sand molding, and you might be able to find a book at a library to tell you about it. But Dave Gingery's book will tell you how to do it pretty well. So get the book! These instructions are very, very condensed. Don't spill the liquid metal. Keep the lighter fluid away from the fire.