how to build a vibrating platform?

i need to eliminate the air bubbles which form when pouring plaster of Paris into rubber moulds. so i thought i could eliminate this through low vibration as the plaster is being poured and eventually starts to harden.

Pretty much what NachoMahma says. I use a variable speed drill for the motor and have a metal plate with a bolt going through it, off center. Put the other end of the bolt into the drill chuck.
NachoMahma8 years ago
. An electric motor with an unbalanced load. Like the buzzers on cell phones, only bigger.