: . . .
: The plunger end can also be a challenge, at least it can with the
: 5200. It will set up enough around the piston to prevent a
: caulking gun from moving it. I place a couple layers of
: aluminium foil over the open end of the cartridge as tightly as
: I can, and then wrap with electrician's tape to compress the
: foil tightly around the steel rim around the edge of opening. If
: you have a small silica gel packet (an active one) to put in
: there before you cover the opening, so much the better.

: Pl Premium, like most single component polyurethanes, uses a
: moisture catalyzed cure, so if you keep the moisture from it, it
: will probably keep reasonably well. I haven't tried putting the
: whole tube in a container with a good sized silica gel pack, but
: this might work even better than what I have done so far. I look
: forward to trying the golf ball trick on my next tube. :)

: Best regards,

: Allan Edie

Perhaps a quick shot of WD40 into the plunger end would work?