On Thu, 29 Jul 2010 13:13:37 +0100, John Rumm
wrote:

Depends on where the valves are in the gun. Mine has a sprung ball valve
near the inlet, and then a second on the outlet itself (formed from a
long rod attached to the trigger that runs up the length of the delivery
pipe). IME you will always get a bit of seepage on the can end since
there will be wet foam about that was moments ago constrained by
pressure from expanding, suddenly exposed to moist air.

I had seepage from the can end which was surprising since no foam,
only propellant, was coming from the other end! But I had heard a
quiet hiss from the nozzle when the trigger was locked, so I'm sure
something isn't shutting completely.

The foam will conform to any odd shape or size gap - so you can position
the board where you want it and let it set - even if that means at one
place its 10mm from the substrate. You would need one big pile of
gripfil to deal with a gap like that.

Luckily I didn't have any big gaps to fill, but I see your point. But
if fitting closely, I think grip adhesives would be just as good?

Yup foam cleaner is basically acetone. Probably about the only way to
buy it in larger quantities these days!

So do thinners do nothing to foam then? I wonder whether I got that
idea from?

Thanks.