QC#57 – Making the “Flower Pot” Foundry

A simple backyard foundry, artfully disguised as a flower pot. (Made for less than $20, and usable the same day!)

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“Quick Clips” are clips of random experiments in a minute or less.

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Music By:
Music by Jason Shaw (RP-Clattertrap)

Project Inspired By:

This foundry is an original design, which comes after months of experimenting, and over 10 different prototypes. The functionality is founded on ideas I collected while searching the internet for foundry designs.

WARNING: Charcoal foundries can reach temperatures in excess of 1,000ºC, which is well above the melting point of hobbyists. This project should only be attempted with adequate knowledge and training, proper protective safety gear, and in a fire resistant area with adequate ventilation. The sparks flying from the foundry can ignite fires, and the fumes from burning dross can be toxic. Use caution and common sense. Use of this video content is at your own risk.

Project History & More Info:

This video is a quick overview of how I made my backyard foundry.

The insulating lining probably isn’t as resilient or long-lasting as a refractory cement, but it can be made quickly and cheaply with very common materials.

In my experience, the sand/plaster lining is durable and lasts long enough to satisfy any backyard hobbiest, so long as you’re gentle and respect the foundry. Slight cracking may occur after a few firings, and that’s normal and doesn’t affect performance significantly. I haven’t had to replace a lining yet, but if you wanted to, it would be really easy to knock out the plaster, and mix up a new batch, reusing the steel pail.

I made 10 different prototypes and experimented with various ratios of portland cement, sand, perlite, plaster of paris, water, and even kitty litter. I ended up favoring the galvanized steel pail, and a mix of 50% plaster of paris, and 50% play sand, by volume, which was inspired by a video by NightHawkInLight “How to Make a Soup Can Forge” http://bit.ly/IBSoupCanForge

All my materials were from Home Depot. One bag of play sand ($3), and one bag of plaster of paris ($16) are enough to make 2 complete furnaces with lids. The steel pails were $10 each, the U-bolts were $1.50 each, the plastic buckets were $2.27, making the total cost for two of these furnaces $46.54 ($23.27 each). Spray paint is an optional touch, and I used “Burnished Amber” to give mine the forged bronze look you see at the end of the video.

Full step by step instructions will be in the tutorial on January 13th

The purpose of my backyard foundry is to demonstrate the most basic setup for casting metals. However if you plan to attempt this approach yourself, some important things to consider beforehand are as follows;

– Soda cans work really well, however aluminum cans are one of the worst sources for aluminum to cast with, and some soda cans in the UK are actually made of steel. The alloy was meant for extrusion, so is not the best for casting. They also produce more dross (slag) because the thin walls oxidize quickly and the plastic coatings on the cans add impurities. A better source of aluminum for casting would be cast aluminum items from thrift stores, like electric skillets or small engine blocks from lawnmower shops.

– The crucible I used was steel, but it’s important to note that steel can be soluble in molten aluminum. It’s possible that when you lift the crucible out of the foundry, the bottom can dissolve out and drop molten aluminum onto you feet and onto the ground. A good refractory crucible can be purchased for about $30 online.

– Lastly, casting over concrete poses risks of steam explosions. If molten aluminum falls to the ground, it can superheat the moisture in the concrete and cause it to spall (steam explosion) where the aluminum lands. This can potentially send hot concrete and molten aluminum spraying everywhere. When possible, melt and pour metal over sand to minimize risks.

Note: Wearing polyester gloves like the ones I had in the video is risky because the material can melt into your hands if you get splashed by hot aluminum. This can potentially leave burns where the metal lands, ringed by plastic burned into the skin.