| Much of it is burned off, but there are constituents that remain and need to be removed. This is called "dross". https://en.wikipedia.org/wiki/Dross You can actually witness the formation of dross yourself if you make your own aluminum foundry (which is ridiculously easy if you have hair dryer, a coffee can, an empty propane canister, and some charcoal). My understanding is that aluminum oxidization contributes somewhat to this, but it's also caused by what's left over after the plastic and paint have burned. Granted, I am in no way saying that recycling aluminum isn't 100% worth it. I was merely trying to address the issue before someone might have brought it up. (I've noticed some people despise the use of absolutes and always need to point out that nothing is absolute) EDIT: For anyone interested in "recycling" their own aluminum, this is almost exactly what I did about 10 years ago, and it was a lot of fun. This guy's casting looks dreadful, though. https://www.instructables.com/Quick-cheap-and-dirty-aluminum... There are other tutorials that describe using a soup can as a crucible, which might work for a short time but I think that's pretty dangerous. |