What’s that Stuff Growing Under the Table Finish?

A friend has a drop-leaf dining table that sat in front of the dining room windows for a period, but there seemed to be no effect on the finish. However, recently something has been “growing” under the finish and it’s all over the table. It looks like it might be mold of some sort, but there are no noticeable cracks, bubbles, splits, humps, etc. in the finish. Nothing is evident on the surface, just under the finish. There does appear to be some coloring difference where the window light would have hit. The table has not been exposed to moisture or any weather elements. Has anyone ever heard of such a thing happening to finish? Any thoughts on how to clean it up? Thanks for any and all ideas. – Paul Kilmer

Tim Inman: Ah for a picture! If the “growth” is black, it is mildew; if it is white or gray, it is probably the finish de-laminating from the substrate. Heat from the sun would “cook away” the finish from the wood. Mildew loves moisture and stagnant air. Mildew is usually easily cleaned with a solution of TSP or other heavy duty detergent, mixed with a little chlorine type bleach. Amazingly, my experience is that if I add a little soap like Murphy’s® Oil Soap, the cleaning action of this brew is really magnified. Underneath the finish, it will be tough to clean. Also, be careful. Cleaning mildew below grade, so to speak, can open the micro pores which are almost certainly in the finish film, and cause more damage than you had in the first place. If the finish has delaminated, then unless the original finish is a traditional lacquer, you’re probably looking at a total finish replacement. Old time lacquers can be resolved and repaired in place.

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