blast cabinets

[Eric J Petrevich/LRM<inchman@prolog.net>]

I have a small problem with my blast cabinet.  I'm using AL-Oxide for media 
and the air pressure is about 100psi.  (note, my air compress give ~16 CFM@ 
100psi.)

When I start blasting, I only get media in the first "spurt" of the 
trigger.  Then if I release and pull the trigger again, I get blast on that 
first spurt again.  If I hold down the trigger, I only get air. So I have 
to keep on squezing the trigger and releasing it to blast objects.  Any 
ideas what causes this?
TIA

Inch