I saw a picture once of wood samples placed under a microscope. One was cleaned with bleach the other with sodium percarbonate. The sample of the bleach cleaned wood looked like a tangled mess and the author of this particular page concluded that this method (bleach cleaning) resulted in serious penetration issues for any type of sealer. This guy made a convincing arguement and he was some tree hugger with nine hundred initials like Phd, etc so I guess he knew his stuff. Take from this what you will.