I have a pallet load of redwood (dressed) various board sizes but
approximately 150mm x 25mm x 3M each. I had them stored outside under two
tarpaulins (cheap B&Q ones). Obviously not really up to scratch for this
purpose and I have only uncovered them to find that the damp/wet has got in
and a number of them are covered in the black/grey mould (or whatever?).
It's not thick at all in fact it seems more like it has stained the wood
rather than coated it. This lot cost quite a bit to buy so I want to salvage
as much as possible.

Does anybody know of a cleaner that will get rid of this or suggest what is
the best course of action to remedy the problem.

Many thanks,
Neil