Rog,
Storing them in a mason jar with an inch or two of linseed in the jar
to keep the rag from drying out, and with the cap screwed on works
well... The rag heats from slow oxidation of the millions of
microscopic crevices of just barely dampened fibers with the oil
(surface area phenomena) deep inside the folds of the cloth with the
R-value of the cloth storing the temperature rise, driving the
process... That won't happen with a sloppy wet rag in an O2 limited
environment...

denny