# Mahogany decking has turned black, need help



## mustangmike3789 (Apr 10, 2011)

this is really unfortunate. this may have happened due to a natural staining that happens with wood that contains tannins/tanic acids. this is done in wood working all of the time. all you need is tanic acid, iron and water. this is noticeable on fences when you see the black streaks running down from all of the nail heads. if you have a high iron content in your water, this could have been the cause or if iron nails were used to build the deck. do not try to clean it off with soap. soap will permanately lock this stain in. normally this staining does not go very deep. you should try to clean it with dish washer detergent mixed with clean water and a nylon deck brush. it will take some scrubbing but it can be removed most of the time. oxalic acid crystals may be needed to get some of the tougher stains. Home Depot may have these crystals in the tile section near the sulfamic acid crystals used for removing grout haze on tiles. i dont feel that this was caused by your paint remover.


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## KarenA1114 (Apr 30, 2011)

*... almost*

Mike, Thank you so much for the information. I used the oxalic acid and it worked on some of the decking; those areas don't have the black stains anymore. Unfortunately, on other parts, it seems as though the stripper did not fully remove some of the original sealer, so the oxalic acid did not get to the wood and those areas still have black stains. I don't know what to do now. I am afraid to use the stripper again because I don't want to make it worse. It is my understanding that mahogany should not be sanded as it would close the pores and then new sealer would not be absorbed. Do you (or anyone else) have any suggestions? Thanks again.


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## mustangmike3789 (Apr 10, 2011)

I am glad the the acid worked for you. Just out of curriosity, did you try the dishwasher detergent. As far as sanding the wood, I can not give you an honest answer on that. I have never heard of that but that doesn't mean that it isn't true. You may want to start a new thread with something to do with wood working. I think that you will be safe to continue with the use of the stripper if you work in smaller areas and don't let it dry on the surface.


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## KarenA1114 (Apr 30, 2011)

Mike, I did not try the dishwasher detergent, I went straight for the acid. It does not appear that the discoloration is very deep in the wood as you mentioned in your first response. I will try dishwasher detergent, water, and a scrub brush next, on a small spot first. If no luck with that, I may try sanding. I read on one website that sanding mahogany with a power sander was not a good idea, but on other sites, people say they have done it and had no issues. It’s hard to know what to believe. Thanks again for your help. I appreciate it.


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## hyunelan2 (Aug 14, 2007)

From what I've read here, sanding will only close the pores if you use too-fine of a sandpaper. If you stick to the really gritty stuff (like 60), you should be able to sand it and reseal. At least that's what everyone has said in the other decking threads (though I don't think any specifically mention mahogany).


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## KarenA1114 (Apr 30, 2011)

hyunelan2 - Thank you for the information. I probably would have bought the wrong sandpaper. I'll try sanding and also the dishwasher detergent on a couple of different spots and see which works best. I have over 200 square feet of decking to prepare for new sealer. Using a sander would probably be a lot faster. The nails should not be an issue either since the deck is fairly new.


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## hyunelan2 (Aug 14, 2007)

Just be sure to practice in a small, less-noticeable area. If the sanding doesn't work out, you don't want a bad spot right in the middle of your deck.


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## KarenA1114 (Apr 30, 2011)

To follow up, the mahogany is in good shape now. I sanded all the decking using a 3" x 18" belt sander with 50 grit sandpaper. This made a big improvement. I then used the 2-in-1 Wood Prep solution again to brighten the wood a little more and prepare it for new sealer. After letting the wood dry for 24 hours, I applied two coats of Behr Waterproofing Wood Finish. Hopefully, I'm done with this for a while - the label claims the finish will last two years. We'll see!


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## chrisn (Dec 23, 2007)

KarenA1114 said:


> To follow up, the mahogany is in good shape now. I sanded all the decking using a 3" x 18" belt sander with 50 grit sandpaper. This made a big improvement. I then used the 2-in-1 Wood Prep solution again to brighten the wood a little more and prepare it for new sealer. After letting the wood dry for 24 hours, I applied two coats of Behr Waterproofing Wood Finish. Hopefully, I'm done with this for a while - the label claims the finish will last two years. We'll see!





Good luck with that.:whistling2:


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## mustangmike3789 (Apr 10, 2011)

yes, the label will probably last two years. as far as the product behind the label, good luck with that. maybe i should have went further in my last post to you by recommending a good sealer for your deck.i was only trying to help with the problem that you were facing at the time. we seem to get a lot of heat for steering people away from Berh paints.:furious:


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## KarenA1114 (Apr 30, 2011)

I would welcome suggestions for a good sealer to use next time. I live in the northeast. I used the Behr because I had already purchased it and wasn't sure what else to use. Consumer Reports' highest rated product is a solid stain, which I don't want. I wanted a clear finish, no tint, but those seem rare. Cabot has a sealer that says it's crystal clear, but I wasn't sure if it is a better quality product than Behr. The one I used is transparant/natural, which has a yellowish tint. I can live with it for now.


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## chrisn (Dec 23, 2007)

KarenA1114 said:


> I would welcome suggestions for a good sealer to use next time. I live in the northeast. I used the Behr because I had already purchased it and wasn't sure what else to use. Consumer Reports' highest rated product is a solid stain, which I don't want. I wanted a clear finish, no tint, but those seem rare. Cabot has a sealer that says it's crystal clear, but I wasn't sure if it is a better quality product than Behr. The one I used is transparant/natural, which has a yellowish tint. I can live with it for now.


 
Better quality product? No question about it.:no: Do some research and see for yourself.:yes:


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## oh'mike (Sep 18, 2009)

mustangmike3789 said:


> we seem to get a lot of heat for steering people away from Berh paints.:furious:


Steer all you want!:laughing:


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## housepaintingny (Jul 25, 2009)

The next time I would use Cabott Australian Timber Oil. It works great for hardwoods and accents mahogony nicely. I would stay away from the Behr Cleaner and Stains in the future. The next time strip the deck, clean with a per carbonate deck cleaner, such as Wolman Deck Brite, brighten and apply one coat of a quality penetrating stain


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## chrisn (Dec 23, 2007)

housepaintingny said:


> The next time I would use Cabott Australian Timber Oil. It works great for hardwoods and accents mahogony nicely. I would stay away from the Behr Cleaner and Stains in the future. The next time strip the deck, clean with a per carbonate deck cleaner, such as Wolman Deck Brite, brighten and apply one coat of a quality penetrating stain


 This is the key word.:thumbsup:


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## KarenA1114 (Apr 30, 2011)

Thank you all for your advice. I definitely *won't* use the Behr products next time. I sure don't want to go through this ordeal again!


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## chrisn (Dec 23, 2007)

KarenA1114 said:


> Thank you all for your advice. I definitely *won't* use the Behr products next time. I sure don't want to go through this ordeal again!


:thumbsup::yes:


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