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Old 16-09-2008, 14:25   #1
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Teak wood blackened spots, any cure?

Somewhere in the past, prior to my ownership, I think water has wicked up under the teak cabin sole on my boat.
The wood (teak) sole has blackened in some spots, noticeably where the wood is fastened/screwed down to stringers.

I have sanded the black spots, bleached them and thought they were "fixed" only to find as soon as they are given a finish coat, they magically re-appear.

The center of the cabin passageway doesn't have any spots. They are only at the outside edge boards, which leads me to think, when sailing healed over, bilge water may have intruded.

Does anyone have the secret to refinish without replacing wood? I have suspicion replacement is the only cure.

I know if there is any solution, someone on this site will have it.

Thank you in advance,


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Old 16-09-2008, 17:14   #2
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I have used wood bleach in the past but I recall it worked only on bare wood. I have a cabin sole with the same issue. Looking for some help here also.

Will & Muffin
Lucy the dog

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Old 17-09-2008, 05:57   #3
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The problem is that although you've treated the surface, the moisture is still in the lower ply's of the decking and it migrates to the surface over time. If the decking cannot be removed, you'll need to leave the surface unfinished for some time. If you have decking that can be removed and you can get at the back/underside, you can drill a series of holes into the decking (but not through!) in a regular patten that can later be filled with epoxy paste. It is a very time consuming process but by opening up the grain, the moisture can be "wicked" out by laying the decking out in a dry environment. You can somewhat hasten the process by applying a low level vacuum to the back of the decking. I've done this by "vacuum bagging" the decking with plastic and then leaving a shop vac run at low speed with the nozzel taped in place through a hole in the plastic. If you cannot remove the decking to get at the back side, you can still use the "hole" method although you would use fewer of them and later plug them with matching teak plugs.

Good luck!

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Old 29-10-2008, 12:07   #4
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I ran into a similar problem with my bulwarks, made of red fir and were fiber glassed over, when I had removed half of the fiberglass on one side I found large black and/or dark spots....too late now, I have to continue on and take it all off. I found to get the dark pots light was alot harder (actually impossible) than gettign the light places dark so I stained them with a walnut stain.
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Old 29-10-2008, 13:18   #5
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Hylyte has an excellent point, you first have to stop the source of the water first.

There is a little confusion about the term "bleaching wood" that people sometimes use. Bleach (sodium hypochlorite) is a base since it has more negative than positive ions, which is the definition of a base. An acid is needed to return wood back to its original brown color. For cleaning really dirty teak you first need to apply a detergent (base) and rise it well. You then need to apply an acid to bring back the original brownness of the wood.

I would try stripping off all the finish and try a teak cleaner kit with a part A (detergent) and a part B (acid)

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Old 29-10-2008, 17:00   #6
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When I was sailing on the w-class boats we used many bottles of dry cleaning fluid to wick the stains of just about anything out, I can't guarantee this but it might be worth the try before any other drastic measure. I know it gets grease out of the teak and red wine as well as other hard to clean substances.
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Old 29-10-2008, 17:22   #7
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svHyLyte and DavidM are right on. Sounds like you have a combination of things working against you, all caused by moisture.
When trees grow they absorb water-soluable minerals which are then deposited in the wood. Being water soluable they dissolve again when the wood gets wet and they migrate to the surface where they are deposited as the moisture evaporates. This makes dark brownish stains. Second, moist wood is a playground for mildew (there are over 1,000 forms of the stuff) and when it grows it makes the area look black or dark gray. I think you have a combination of these two.
First you must get the wood DRY .... REALLY dry. All of the finish must be removed to accomplish this so the moisture can evaporate. If you can get the wood out into the open where sunlight can get to it and air can circulate all around it it will dry much quicker. If you leave it in place at least run a fan at low speed over it. In place the drying could take several days.
Once dry, one of the two step teak conditioning kits would work - one step to remove the stains, the second to kill the mildew spores and bleach the wood back toward its original color. Use step two sparingly so as to avoid over-lightening the wood.
Once the stains have been removed you must first make certain that the source of the original water is stopped, and ideally the BACKS of the boards should be treated with a water-repelling oil treatment. then, and only then, should you refinish the tops of the boards using a good polyurethane finish. You'll probably never get the whole floor to march completely, but this should at least make if look good again.
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Old 23-11-2008, 10:19   #8
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Thanks for the ideas and information everyone.

I will try them. With much appeciation for the helpful thoughts.

Thank you

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Old 26-11-2008, 11:15   #9
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Semco 2 part teak cleaner and brightener...

Just stripped the teak on our CSY 33 and then used the Semco 2 part cleaner and brightener. It worked VERY well for the exterior teak.

The Semco teak sealer is nice stuff as well, I like the simplicity and ease of application.

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