Originally Posted by mattathayde
pretty much has been hit right on the head so far but i will add something.
it has been said that the metal gives off gases or something bad (at least some of them have been said to). im not sure how true this is but i personally dont want to use them until i know the exact alloy of the metal and have results of how that metal reacts to heat ( alloys with zinc can start to give off their zinc around 500ish *F iirc and zinc poisoning is very very bad). if its pure AL then i would give it a try if i was bored.
in the end it comes down to what is more consistent, if you can get them to work then use them but for me its one more thing to clean and i dont think it will work as well as foil
For the metal to give off those fumes it would first have to reach its melting point, then its boiling point. Unless you see pieces of molten metal in your bowl after smoking it, you can use it.
and most brass contains some zinc