I'm asking this for a friend, so the facts are two people removed, but it's a question we may be ablew to answer here.
A FOAF has a piece of Arts and Crafts furniture, which I presume is made from quartersawn oak. But this piece develops a growth of blackish mold every so often. The owner has tried a variety of cleaners, bleaches, etc., to no avail: the stuff keeps coming back. My friend would like to either a) tell the owner what can be done with it to cure the problem, or b) know what can be done because the owner's ready to trash it, and my friend's ready to trash-pick it and fix it up.
Any suggestions, based on this admittedly sketchy information?