[Fred Hargis]

Oil based finishes have just about an indefinite life, until the can is opened. That allows the start of the curing process and it won't be long until it's, well, cured. That's waht you are seeing. You can do things like Dave suggested (and a few others) to slow it down, but it's best not to expect it to last too long once opened. Keeping it in a refrigerator also helps. For what seems to work best is to either 1: cover the finish with a piece of wax paper cut to fit inside the can, or 2: fill the finish can with something (marbles) until it's full enough to push almost all the air out.

 

[Fred Hargis]

I've tried vacuum sealing (believe it or not) a couple of ways. The first, I actually cut the port out of one of those Ziplock vacuum bags, and put it on a paint can lid for a can of varnish. I had perforated the lid right under the port to draw a vacuum. Really worked (the vacuum part) since I could crush the can pumping the air out. But it didn't seem to help. Next I tried just using a gallon size Ziplock, put the quart can in there, and then suck it down. That didn't seem to help either. I'd like for someone else to try it and see what happens. Maybe my method needed to be tweaked. Anyway, the pint jars should help, if the finish fills them up.