: Does epoxy have a shelf life?

My West system stuff is about 18 months old (and I bouhgt in quantity,
so it should do at least one and maybe two more boats yet). The resin
seems to have no problems, but the hardener goes off where it is in
contact with the air - it can't be being oxidised, since it is an
oxidising agent, but maybe it is hygroscopic. Anyhow, it goes "stiff"
and becomes very hard to clean off - my metered pump basically seized
up and even having dismantled it, I can't seem to get it cleaned up -
resin removing cream doesn't shift it, and vinegar has no effect.

However, even using hardener which is obviously in this state (I did
a test using some which had been left in an open 35mm film canister for
a couple of weeks) it seems to work fine. Maybe if it has absorbed water
vapour, it will behave a bit like resin used in high humidity and get more
amine blush than usual, but on the test piece I did, it seems to have
worked OK.

Anyone out there have any ideas of how to de-gunk the metered pump ?

Andy