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Making Green Sand
I've wanted to cast metal for a long time. I've had the equipment, the supplies, green sand, and everything else ready for months now... well, I finally got around to it!
Making Green Sand
Green Sand is used for metal casting. Simply put, it is a mixture of sand, bentonite clay, and a bit of water.
Bentonite is used in clumping cat litter, so to make green sand, I ground up some cat litter in a ball mill of my own design.
The drum is a 5-gallon paint pail, turned at 32 rpm. The grinding media was about 2.5 gallons of crushed granite rocks, ranging in size from 1" to 3". Six pounds of Tidy Cat clumping cat litter were dumped on top of the rocks, and the drum turned for 1.5 hours. This ground the cat liter very finely. (If you do this, wear a dust mask when you handle the bentonite.)
The ground bentonite (I guess you could call it "cat litter flour" - yuck) was added to a 5-gallon bucket of "fine" masonry sand. The bucket contained nine inches of sand, so I added one inch of bentonite to achieve a 10% bentonite mixture, and mixed the two dry for about ten minutes. I added about 32 oz water in six ounce (coffee cup) increments, mixing constantly between additions, over a period of several hours. I stopped adding water when the sand started to display "packability", or whatever you want to call it. Here is my Dave Gingery imitation...
I squashed a handfull of sand into a lump, and broke it in half. It held it shape quite well, and broke cleanly.
Continue to making the mold.
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I have seen so many recipes for Green sand it boggles the mind. Have fun with the casting, make sure that your moisture level is low. Believe me, you don't want a steam explosion on your first cast. Not pretty.
ReplyDeleteI have been using used motoroil as the liquid content and it seems to do quite well. My casts have been nice and shiny so the cooling is still fast enough to keep heavy crystal build up in the surface of the melt. It smokes a bit and on larger casts there is some flaming at the vents but I haven't had anything serious go wrong. I am still developing my ramming technique. Sometimes too hard and I get some 'flaking' at those points, I guess because the sand can't absorb the vapors. Its a learning curve though.