This tends to exclude many common household objects and much of what was owned by the middle and lower classes. The following discussion outlines some of the options to consider when choosing a finish for a period piece. It is certainly true to say that one form of period finish was to have no finish at all, particularly for domestic or utilitarian pieces. Homebuilt benches and stools may have had little more than a cursory removal of the worst splinters. However, in an environment with little temperature or humidity control, as well as numerous pests, untreated wood isn't likely to enjoy a long and useful life.
Surface treatments help to seal out moisture and discourage insects.
There is, unfortunately, almost nothing written in period that addresses specifically how the surfaces of common furniture were treated. However, it is probably safe to assume that the techniques known to artists might also be known to other trades, such as carpenters and joiners. It is also quite possible that the finishing and decoration of furniture was left to specialized painters if the owner wanted something beyond raw wood. In looking at period documents, one must be careful in making assumptions based on modern definitions. There is evidence that carpenters in the14th century treated interior woodwork with oil and varnish, sometimes colored with ocre 2 .