Cleaning residue on stained deck?


I have a natural cedar deck that I pressure washed and then stained with semi-solid this past spring. Came out quite nice.
A good portion of this deck in under a maple tree on one side and oak trees on the other. Over the past few months, even though I kept blowing the leaves off the deck, there has been a buildup of a black residue on the deck. I tried scrubbing this with a soap and water solution without success.
Can anyone recommend a solution that will soften/emulsify this residue hopefully without harming the stain below it?
Any advice greatly appreciated.
B
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What happened last year, didnt the stains go away. I use laundry bleach sprayed on from a garden sprayer about every 6 months. I have alot of shade and find for me the dark areas are mold, it should work on leaf residue. Bleach wont hurt deck stain. If after you spray the bleach turns white it is mold growing.
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Bob M wrote:

Is the black color simply darkening, or is there something gummy/stick? If it is sap from trees, mineral spirits and stiff brush should take most of it off. If it is simply staining from tannin in leaves, it probably won't come off (unless bleach works on it).

Why do people use good wood like cedar and then paint the stuff? Kind of like buying gold jewelry and having it tin plated :o)
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snipped-for-privacy@earthlink.net wrote:

When the desk was first constructed to replace on old pressure treated one, the white cedar was stained with Sikkens Cetol CRD. For the first year the deck look like a piece of fine furniture. And that's one reason why we selected cedar in addition to its longevity properties. However, starting the 2nd spring, it severely darkened and bubbled in places to the point where we actually had the wood rep and the sikkens rep both visit at the same time. Of course they both pointed fingers at one another. Bottom line, we were stuck so the only thing I could do was pressure wash the deck to remove as much of the bubbling/peeling/residue and possible, let it dry for a couple of weeks then apply a semi transparent stain this past spring. It looked pretty good until the dark residue started this fall.
One responder mentioned that it might be mildew which I could remove with a weak bleach solution. I haven't tried that yet with the fall leave tasks, but now that that's done, the bleach is my next job.
I hope I answered you question about covering up nice wood. Even though I did my homework on this new deck and selected materials and finishes based on the results, after the honeymoon the look went away.
Later - Bob
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Bob M wrote:

I was mostly teasing about coating cedar...I expect I will never have a cedar deck. If I did, I'd let it weather naturally and expect it to outlast me :o)
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