Multiple screens (5+) work just fine without liquid leaking if you follow the below procedure.

Get a good torch and hold the thin flame just in the middle above the glass, while sucking.

The carbide should get redhot on the top without touching the flame if you are doing something right. Once that happens breathe out, then inhale the vapor slowly until your lungs are filled.

be sure the torch goes off properly as in less then ten seconds your serotonin receptors will be carpetbombed by dmt molecules.

If you feel good about it repeat the above.