Head in Glove

Walked down the High Street this afternoon, for the first time in ages. 

The street performers are mustering. Three living statues, a couple of caricaturists, the mandatory piper, and this guy.  

His act appeared to consist of sticking a vinyl glove on his head and blowing into it so it slowly got bigger and bigger, until eventually it exploded and fragments flew all over the place.

I watched for a bit. Still baffled. What was I just not getting?