THE CRAFT OF FIRE

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...

We finally melted some aluminum! The kiln, loaded up.  We're not ready with our plaster molds, but we decided to just fire up the kiln and make some ingots out of the aluminum we had collected. The melting point of aluminum is 660° celsius, but we had to get the pyrometer reading up to about 930° C before the metal in our tin-can crucible (not really tin, not much of a crucible either) would melt. The soup-can crucible fared much better when the flame wasn't blasting it straight on. So we figured it's just the difference between what the pyrometer is reading—placed perhaps a little too high up in the kiln, with the hot air rushing by and out of the vent up top—and what temperature the metal is actually at, down below. A bit more of a spread than we had figured, but metal doesn't lie: it melts at 660° C and don't you try telling it otherwise. Unless of course it's not pure aluminum. But the heat sinks from the computer are—almost 99.5% pure, ...