# Black Spots on the deck



## trowe727 (Mar 8, 2012)

This is my first time that i have posted on here.

I am in the process of stripping a redwood deck. It had a solid stain on it before and I was able to pull up most of the stain with the pressure washer(using the green tip). There were some areas that I spot stripped and everywhere the I applied the stripper the wood turned black. I used the Deckscape stripper and hit it with DS revive after and the wood is still discolored. I dont want to keep hitting the wood with the pressure washer and it goes very deep into the wood. Any suggestions?


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## SeattleHomeServices (Sep 20, 2012)

trowe727 said:


> This is my first time that i have posted on here.
> 
> I am in the process of stripping a redwood deck. It had a solid stain on it before and I was able to pull up most of the stain with the pressure washer(using the green tip). There were some areas that I spot stripped and everywhere the I applied the stripper the wood turned black. I used the Deckscape stripper and hit it with DS revive after and the wood is still discolored. I dont want to keep hitting the wood with the pressure washer and it goes very deep into the wood. Any suggestions?


Stop power washing the deck ... its like using water on a grease fire in this case. The water is causing tannins to leach out of the wood. 

Assuming it's tannins I did a little research. You can mix hot water and oxalic acid and it should (with the right concentration) eliminate the black marks.

The other issue could be mildew in which case you'll use bleach-water.

Maybe call a lumber yard that sells redwood and double-check ...


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## trowe727 (Mar 8, 2012)

I stopped pressure washing it, but I've never seen this. It turned black even where the stripper ran down the railing, so you can see the stream where the stripper was on the post. The rest looks fine. It's a little fuzzy, but not bad.


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## Custom Brush Co. (Jan 26, 2011)

I've had this happen before, after the deck dried seemed spots went away. Using a wood bleach as mentioned above (oxilic acid) can work. Trying to take solid stain off & go to a semi-trans is going to be a difficult one to please picky clients. Hard to get perfect wood finishes outside without spending lots time & money. I always try & sell solid stain in these cases.

You might mention to not expect perfection in color uniformity.


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## 1963 Sovereign (Dec 14, 2011)

call pressure tek in ohio ,you need some chemical brightener,to counteract the stripper.(which in fact may be oxalic acid if memory serves me


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