Aluminum Session No. 2
So, last time we melted aluminum, we had this idea to use charcoal to try to reduce the amount of oxygen mixing with the aluminum in the crucible. Well, we tried it.
But first, just to get into gear, we melted down some more computer parts that we had. A big heat sink and some smaller ones, totalling 538 grams (the can weighs 87, for the 625g as seen here).
All of this came out very well, and we ended up with four ingots weighing a total of 503 grams. That, plus the dross of about 37g came to a total of 540 grams. When you factor in the 87g of the can, we get... 627g. Two grams more than we stated with! And there it is: the Law of the Conservation of Energy destroyed right there in our garage!
Hahaha. (Okay, so our measuring is not exactly scientific. But more or less we got out what we put in.)
It was cool to see the shape of some of the heat sinks, almost reduced to ash. Maybe it has a thin coating on the aluminum that doesn't melt down. Dunno. But you can see the flaky fins of the heatsink here in the can:
And when everything cooled we could peel off this layer of what was essentially aluminum foil from the inside of the can:
Next, we tried some pop and beer cans without charcoal, in the new 'crucibles' that I found behind a local Italian restaurant.
We tried crushing the cans even more than last time, as thin as possible (to reduce the air space), but there's only so much you can do about empty space when you drop them in the can.
These came out full of dross like last time.
But there was a nice chunk of metal under everything that, after cleaning up, should be pretty good.
Finally, we did the charcoal experiment. We filled up another tomato-crucible with cans, then poured in all the activated carbon that we had (you can buy it in aquarium stores; it's for the water filters).
It wasn't really enough so we added wood charcoal as well, trying to pack the crucible as much as possible.
We fired it up like everything else to a pyrometer reading of 950 C (although that is not an accurate reading for the actual metal in the can), and then pulled it out for pouring:
But nothing came out.
So we poked at it a bit and tried to see what was going on:
You could see shiny bits (not entirely clear in the photo), but the metal was there.
It looked like it needed more time so we put it back in the kiln and kept firing.
And then we tried again:
As far as we could tell, there was no discernible difference between this batch and the previous one without charcoal. The aluminum is there, but there's still so much dross connected to it that we have concluded (as others have before us) that it is indeed possible to get aluminum from all-pervasive pop/beer cans, but it's not really worth the trouble. Much better is to find yourself an old desktop and extract a couple nice chunks of pure aluminum from it. Because from the two computers that we salvaged, we got nearly a kilo of aluminum, and from the 60 pop cans we burned (about 840g), we got, after much labour separating as much dross as possible from the usable metal, maybe 220 grams? Say goodbye to the bags and bags and boxes of cans in my garage that we've been collecting for this purpose - in the Recycle Bin they go.
For anyone interested in still trying with cans, an acquaintance, Scott, sent in some interesting info in reply to a post of ours on FBook: "Aluminum cans have an internal polymer layer to stop acidic beverages reacting with the can and disintegrating it in short time. That layer and external print would be quite a high percentage of the overall can mass. The layer is thermoplastic PVA so, if one could regulate the temperature well, 200 C without flame would see it melt and pool away. Then increase the temperature slowly to melting point of Al, to give time for other impurities to oxidise and gas off."
It's been fun, we learned a bunch trying to make this work, but we figure it's best to move on and not try to solve a problem (how to get aluminum from pop cans) that is not really worth solving. In other words, one of the best ways to solve a problem is to avoid it in the first place (get aluminum elsewhere).
Because, look, if the frame of this old IKEA chair we found in the garbage is made of aluminum as we think it is, we'll have more than enough to work with...
Next session we'll prepare our molds and then be ready to cast.
But first, just to get into gear, we melted down some more computer parts that we had. A big heat sink and some smaller ones, totalling 538 grams (the can weighs 87, for the 625g as seen here).
All of this came out very well, and we ended up with four ingots weighing a total of 503 grams. That, plus the dross of about 37g came to a total of 540 grams. When you factor in the 87g of the can, we get... 627g. Two grams more than we stated with! And there it is: the Law of the Conservation of Energy destroyed right there in our garage!
Hahaha. (Okay, so our measuring is not exactly scientific. But more or less we got out what we put in.)
It was cool to see the shape of some of the heat sinks, almost reduced to ash. Maybe it has a thin coating on the aluminum that doesn't melt down. Dunno. But you can see the flaky fins of the heatsink here in the can:
And when everything cooled we could peel off this layer of what was essentially aluminum foil from the inside of the can:
Next, we tried some pop and beer cans without charcoal, in the new 'crucibles' that I found behind a local Italian restaurant.
We tried crushing the cans even more than last time, as thin as possible (to reduce the air space), but there's only so much you can do about empty space when you drop them in the can.
These came out full of dross like last time.
But there was a nice chunk of metal under everything that, after cleaning up, should be pretty good.
Finally, we did the charcoal experiment. We filled up another tomato-crucible with cans, then poured in all the activated carbon that we had (you can buy it in aquarium stores; it's for the water filters).
It wasn't really enough so we added wood charcoal as well, trying to pack the crucible as much as possible.
We fired it up like everything else to a pyrometer reading of 950 C (although that is not an accurate reading for the actual metal in the can), and then pulled it out for pouring:
But nothing came out.
So we poked at it a bit and tried to see what was going on:
You could see shiny bits (not entirely clear in the photo), but the metal was there.
It looked like it needed more time so we put it back in the kiln and kept firing.
And then we tried again:
As far as we could tell, there was no discernible difference between this batch and the previous one without charcoal. The aluminum is there, but there's still so much dross connected to it that we have concluded (as others have before us) that it is indeed possible to get aluminum from all-pervasive pop/beer cans, but it's not really worth the trouble. Much better is to find yourself an old desktop and extract a couple nice chunks of pure aluminum from it. Because from the two computers that we salvaged, we got nearly a kilo of aluminum, and from the 60 pop cans we burned (about 840g), we got, after much labour separating as much dross as possible from the usable metal, maybe 220 grams? Say goodbye to the bags and bags and boxes of cans in my garage that we've been collecting for this purpose - in the Recycle Bin they go.
 |
| Bags and bags and boxes and boxes of cans |
It's been fun, we learned a bunch trying to make this work, but we figure it's best to move on and not try to solve a problem (how to get aluminum from pop cans) that is not really worth solving. In other words, one of the best ways to solve a problem is to avoid it in the first place (get aluminum elsewhere).
Because, look, if the frame of this old IKEA chair we found in the garbage is made of aluminum as we think it is, we'll have more than enough to work with...
Next session we'll prepare our molds and then be ready to cast.
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