Breaking glass with sinus tone.

In technology class we always try to push the limits and lately we've been trying to break a wine glass by analyzing it's resonant frequency and replay it with a sinus generator at very loud volume.
First of all it doesn't work with normal wine glasses, cristal is best and is easy to resonate by making your finger wet and rubbing it over the edge of the glass in circles (you know the old trick) we managed to vibrate the glass to a certain point but the breaking didn't occur....Probably not enough juice from the speaker next to it!
Anyway you can try this experiment at home it's pretty cool!

Here's footage from a university who did succeed and filmed it in highspeed!