There’s a tip on the Fine Woodworking* website at the moment about preserving finishes. Peter Limon suggests using a vacuum pump on mason jars to remove the air to prevent oxidation. Because I use quite a bit of varnish, stain and oil on boats I’ve often opened a can of last year’s finish to be disappointed with the contents so I hunted around for ideas:

1. Keep a set of jars in graduating sizes. I have a large, tall jar that originally held passata (I think) and various other food jars going right down to a mustard jar. Because it’s not a good idea to use finish straight from the original can I pour out what I plan to use and decant the remainder into a clean jar. The less space in the top, the less oxygen to spoil your finish.
2. Cut out a piece of grease proof paper and lay it on the surface.
3. Fill the jar up with clean, glass marbles to displace the air.
4. Spray an inert gas into the top and put the lid on swiftly. Search online for “wine preserving spray”.

I favour 1 and 3. Cheap, easy and effective.

*You’ll need membership to find it. I tried to post this on their forum but the spam filter got it!

St.John