Don Bruder wrote:

It does sound suspiciously piezo to me... What "flavor" sand was being
used? If it's a quartz based sand, rather than the more usual "silica
sand", that might go a long way toward explaining it, since quartz does
do the piezoelectric thing.

Can't rule out static buildup, either, but good Sir William's shaving
device leads me to lean toward piezo effects as the source.


Aloxite grit does it too, its an electrostatic effect, caused by the
particles being charged by friction as they rush up the pipes to the
nozzle tip. Charge is transferred and stored on the object until the
potential is high enough to discharge away, or it leaks through
something. Certainly you get a stronger effect if you hold the object
away from the walls with the cabinet gloves.

Steve