Looking for something crafty and stealthily artistic? For this project, use sand and plaster to make a simple backyard foundry that can melt scrap metal in seconds, but is still a pleasant decoration. No one will ever know that the houseplant is actually a homemade furnace!
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MINI METAL FOUNDRY
SAFETY KEY:
+ Eye protection
FIRE WARNING:
+ The mini foundry gets so hot on the inside it will melt soda cans within seconds. Use extreme caution.
SKILL LEVEL:
EASY
INTERMEDIATE
ADVANCED
APPROXIMATE TIME:
4 hours
WHAT YOU’LL NEED:
+ 25-pound bag of play sand
+ 25-pound bag of plaster of paris
+ Buckets
2.5-quart plastic bucket
5-quart big-mouth plastic bucket
10-quart steel bucket
+ Steel wool
+ Plastic tablecloth
+ Hacksaw and vise
+ 1 × 12-inch steel pipe
+ 1-inch PVC coupling (Slip × FIPT)
+ 1-inch PVC pipe
+ Two 4-inch U-bolts
+ Spray paint
+ Charcoal briquettes
+ Channel locks
+ 1 ⅜-inch hole-cutting saw
+ 3-inch hole-cutting saw
+ Hair dryer
+ Old fire extinguisher or clay graphite crucible
LET’S BEGIN
MAKING THE MIXTURE
1. First prepare your steel bucket by lining it with steel wool.
2. You can quickly combine the ingredients by using the 2½-quart plastic bucket as a measuring tool to combine ¾ bucket (21 cups) of plaster of paris, 1¾ buckets (21 cups) of sand, and 1¼ buckets (15 cups) water. From the moment the water touches the dry mix you’ll have about fifteen minutes before it all hardens, so immediately use your hands to mix it all up.
3. Transfer the plaster of paris mixture to the steel bucket you previously lined with steel wool. Pour as slowly as is practical to minimize splattering. The mixture should reach three inches from the top.
4. Use the plastic measuring bucket to form the center of the foundry. Fill with water and push the weighted bucket into the center of the steel bucket. The mixture should rise upward but not spill out. Hold down for two to three minutes to set.
5. Using a paper towel and some water, clean up the edges around the bucket. Let sit for about an hour.
6. Dump the water from the bucket. Use pliers or a pair of channel locks to gently pull one edge toward the center. Now grip the channel locks with both hands and give it a twist. The whole bucket should pop loose leaving a smooth hole in the center of the steel bucket.
INSTALLING AN AIR SUPPORT AND LID
1. Center your 1 ⅜-inch (35mm) hole-cutting saw with the top raised ring circling the steel bucket. Once you cut through the metal, burrow down at about a 30-degree angle, which should be fairly easy as the plaster has not fully cured yet.
PRO TIP: We want the hole to be tight and at a downward angle so if the crucible fails, the molten metal will stay in the foundry instead of spilling toward you.
2. Make your blower tube by connecting your one-inch steel pipe to the one-inch PVC using the coupling screw. Twist the threaded side onto the steel pipe and push the PVC through the other end with the slip adapter. Remember that the steel portion is what is inserted into the foundry.
BUILDING YOUR FOUNDRY LID
This will serve as your vent as well as allow you to melt metal without removing the lid.
1. Fill the big-mouth bucket with cups plaster of paris, 10 cups play sand, and 7 cups water. Mix well.
2. Stand two four-inch U-bolts upright in the mixture. You can place a three-inch-wide can in the center of the mixture to cast a vent hole at the start of the process. Or, when the mixture is set, use a three-inch cutting saw to drill a hole right in the center.
3. Wait an hour for the plaster to set and then pop the lid free from the bucket.
PRO TIP: Now’s the time to customize your foundry with spray paint if you want to go the extra mile. Burnished amber Rust-Oleum gives it a nice decorative touch or any other medieval-inspired color. Paint it to your liking!
MAKING THE CRUCIBLE
HEATING UP! A fire extinguisher doubles nicely as a crucible to prove this project could be completed in an apocalyptic situation, but it’s not the only option. You can buy an excellent clay graphite crucible online for around $30.
1. If you decide to use an old fire extinguisher, note that if a magnet sticks to the side, then it’s steel. If it doesn’t, then it’s aluminum and it won’t work for you.
2. Unscrew the valve from the top of the extinguisher to depressurize. Place the tank in a vise and then cut it in half with the hacksaw. The bottom part is now a steel cup three inches in diameter and five inches tall.
USING THE HOMEMADE FOUNDRY
1. Use duct tape to attach a hair dryer to the end of the blower tube. This will supply air to the flames.
2. Toss charcoal briquettes into your foundry, light, and put the lid on.
WARNING:
Charcoal used for barbecuing is specifically designed to make the coals burn slower at a lower temperature, so to achieve a hotter temperature use lump charcoal, which is basically just pyrolyzed wood. Lump charcoal will emit a shower of sparks, so wear long sleeves and gloves. Also use a lower setting on your hair dryer as you don’t need to pump that much air into it to get the same temperatures.
3. Your foundry will soon reach temperatures around 2,000 degrees Fahrenheit, which is hot enough to melt not just aluminum, but copper, silver, and gold. Try melting soda cans and scrap metal. You can also use your foundry as a blacksmith forge, or even to roast hot dogs for a super-charged cookout—it is powered by charcoal after all.
PROTIP: As soon as you turn the hair dryer off, pull the tube out of the metal foundry. If you leave the tube in the foundry with no air blowing, the heat will travel up and melt your hair dryer.
Now you have a handmade mini metal foundry that can reach unbelievable temperatures. And when it’s not in use, drop a potted plant inside and instantly transform it into fashionable home decor. It’s important to remember that this is an entry-level system. If you want to get serious, I recommend investing in proper refractory materials. Let the broiling begin!
FUN FACT: If you could take a time machine back to Mesopotamia in 3200 BC, you would find the first metal castings. Fast-forward to today and metal casting has become a $33 billion industry in the US, with 90 percent of all manufactured products containing some metal-cast part.