I have the answer and S. W. does not like it. MILDEW!

Our company has discontinued the use of S.W. deck stain due to this mildew problem. I am currently responsible for washing 3 separate customers decks for an unknown length of time due to this issue. I used the deck stain on those decks in the summer of 2008 and in all 3 cases less than six months later they turned black. S. W.'s response is "the mildew spore count was too high when you used the product."

Now that logic baffles me because I paint the rest of the house at the same time and have had no mildew issues with the paint.

A product called JOMAX is available for mildew washing. Follow directions and wash twice a year. Sorry for the news.