On the subject of moisture and also of a finish drying out, my experience with old radio cabinets has been limited to either shellac or lacquer. My dad began servicing radios in 1943, and I remember seeing him use olive oil to remove a white water ring on the top of a console radio. I never forgot it and now use it on just about any old cabinet that still has a reasonable amount of finish on it. In a few cases, it has even convinced me to leave an old original finish alone instead of redoing it.

Olive oil works equally well with shellac or lacquer if it has a dried out appearance, although it may take a few applications over a period of as many days to do its best. This is especially true if a stubborn water ring is deeply embedded in the finish. New and old surface scratches are hidden immediately, and stay that way for months or longer. As a test several years ago, I treated ½ of a cabinet and let it set out in the garage for several months. At the end of this time, the difference was still like daylight and dark. I have not made any tests to see what would happen with water spills, but it stands to reason that a surface treated with olive oil may be less susceptible to it.

Olive oil in the bottle will become rancid over time, and stink to high heaven. However, I have never had this happen on a treated surface, including the inside of old battery sets with the lids closed. To keep olive oil fresh, store it in the refrigerator. It turns white and solidifies, but reverts back to an oil at room temperature.