Many times as furniture makers, we will put a finish on the underside of a tabletop to prevent it from warping or cupping. The theory being, if you put the same finish on the top as you do the bottom the moisture transfer will be equalized on all sides, helping to prevent wood movement. Regardless whether or not this theory is true, there are other reasons to finish the bottom of your tabletop.
Continue reading on my blog to see the real reason why I finish the bottom of my tables.
-- What I do in and out of the shop at http://www.BriansBenham.com