i use the glass beads as my screen, i use only four and I put the flat side up so the coal can sit on it. Also you should take the class to a torch to burn off anything that might be on them. I also pre heat the glass with my butane torch. Ive used this couple times and it makes the session much longer mine was 1 hr while with foil it would be 30 min.
i think this is easier then poking holes in foil, its much faster, you get more air but the hits are much more consistant because of the heat from the glass, i think every1 should try it it's defiantly not bad
Would it also be possible that the glass beads would slightly weigh down the tobacco, thus inhibiting air flow, in addition to no air being able to freely flow above the shisha because there are flat-bottomed glass beads pressing down on it? It seems like, in theory, it's a good alternative; however, in reality there are a few of the technical aspects involving air flow that it would seem would make the pull extremely difficult.