When opening a new bottle of Truoil, I have four 35mm film containers; transparent white. I forget which company my wife buys. I fill each container about l/3" from the top and put on the cap. The cap recesses into the container and forms a good seal. You might add a marble or two to bring it right up to the bottom of the cap. I've been working out of one container for over a week now and no scum is trying to form.

Don't sacrifice the future on the altar of today