: There's a commercially available aerosol product called something like
: "Bloxygen" and sold by Woodcraft or Lee Valley. It's an inert
: gas that's sprayed into the can prior to closure...displaces the oxygen to
: prevent skinning over.

: Supposedly it's an inert gas so there should be less potential danger (or
: social stigma :-) )than the propane/methane suggestions.

I bought a can of Bloxygen but haven't used it yet, so I can't report on its effectiveness. The oxygen in the air reacts with the varnish and will cause it to skim over or turn the entire contents of a partially full can to jello. Once it jells thinning won't save it. So keep the can closed as much as possible. Open, stir, pour into a working jar, and cap as few times as possible. Storing the can upside down with one side propped up guarantees an air tight seal on the lid and avoids forming stalactites on the regularlly bottom of the can. Don't buy big cans and store half full for extended times. The mason jars sound like a good plan. After throwing away two quarter-full cans of Captains I bought the Bloxygen.