I've been given four 8' x 6" x 5/4 hit-or-miss quarter-sawn oak boards. Unfortunately they sat in a shed for a year or so and ended up covered with dirt. The dirt has sand and small stone particles in it.
I can brush most of it off, but I'm not crazy about putting it through a planer and wrecking the blades on any ground-in particles. Any ideas for cleaning them off without ruining my planer blades?