how do you clean mold off wood?

vacuum the loose stuff off first with a hepa filter (otherwise you just spread it), then scrub with warm water and a squirt of dish soap, or white vinegar neat. bleach is what the label pushes and it's the wrong tool on wood - it sits on the surface, the roots carry on underneath. dry it fast with a fan. if it keeps coming back the wood is damp from somewhere and that's the actual job. black staining left after cleaning is just a stain - light sand, or oxalic acid wood bleach if it bothers you.