get a 1.25 l coke bottle, put boiling water in it, to make it shrink and harden the plastic, then ptu about 100ml of hydrochloric acid (commonly foudn in most pool sheds) in it, then roll up 3 decent size peice of aluminium foil (do each to about the size of a phat cuban cigar) then put the foil in, put the lid on, tighten it, shake, and sit sub cone over the top!! hehehe
this is not an exsplosive as such, the acid reacts with the foil, creating a hydrigen gas, which heats the plastic, expands, pops (mighty loud btw) and then burns anythign it comes in contact with, thanx to the hcl