My wife and I found possible drug paraphernalia in my son's room?

Sounds like heroin or oxycodone; both of those are nasty drugs to get into. You don't have to accuse him of doing anything but ask him what he was using the aluminum for. If he does suggest it was for a school project then casually ask to see the project. I'm not saying you shouldn't trust him but heroin and oxy are not good habits.