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post #1 of 13 Old 08-22-2012 Thread Starter
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Black spots on the wood

I've been working on refinishing the wood toe rails on my boat. I've had good feedback from Sailnet members on how to remove the old varnish (thread: "Power tool for sanding toe rail") and now I'd like to tap the collective knowledge on this forum on how best to deal with the parts of the rail that have become so aged/exposed/worn that there are very dark spots in the wood. I would guess that this is the beginning signs of surface rot, maybe.

How have other people effectively dealt with this? Should I sand more deeply, bleach it, sell the boat and buy a big-screen T.V.?

Ross
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post #2 of 13 Old 08-22-2012
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Re: Black spots on the wood

Ross,

The discoloration is perfectly normal, and is NOT indicative of rot. What I'd recommend is to begin with the least destructive method first then progress to bigger guns as required.

That said, you probably won't need to go beyond a gentle cleaning with water, a white scrub pad and some Bar Keeper's Friend.


The key ingredient in BKF is oxalic acid, which will bleach out the discolored areas. It also has no abrasive material that will do damage to your teak. Likewise, use the white scrub pad (never a green one) to keep from removing the softer wood between the growth rings.

You could also try a commercial teak cleaner, but I'd try BKF first since it's cheap and a can will last a long time.
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post #3 of 13 Old 08-22-2012
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Re: Black spots on the wood

My experience has been that the dark spots are "mold." I just use household bleach to bleach the spots back to bright teak.
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post #4 of 13 Old 08-22-2012
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Re: Black spots on the wood

Household bleach works fine - may need more than one application.

Wash the bleached spots in fresh water afterwards.

Doing it at this moment on my woodwork.
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post #5 of 13 Old 08-22-2012
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Re: Black spots on the wood

I go with PorFin on the Bar Keepers Friend. If the discolorations remain after a scrubbing with that product, go to West Marine or a paint store and buy powdered Oxalic acid which you can mix to a more concentrated solution in warm water, and then load into either a spray bottle or a small garden sprayer (works best) give it all a good soaking keep it moist until the wood appears uniform. You can do it in stages. I have and do use all sorts of things on teak and exterior woods but Oxalic Acid is far better than alot of people think and need not be used at harsh levels unless you are just plain impatient....If it is giving your hands a good tingle when sprinkled on the back of your hand it is plenty good enough to remove the discoloration and kill most mold or fungal activity. Rinse real well, and if you want to be very very thorough then use a very mild soap to neutralize an further activity. I have recently done this to the Morgan I have and the teak is now fresh and clean as new....this includes the seam area on toe rails where growth has a tendency to hide on older boats
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Last edited by oysterman23; 08-22-2012 at 06:35 PM.
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post #6 of 13 Old 08-22-2012
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Re: Black spots on the wood

They will all work. Wood bleaches vary in strength from sodium hydroxide (very caustic), chlorine bleach (sodium hypochlorite solution) and oxalic acid. The latter two work great without need to neutralize the caustic pH. Using sodium hydroxide requires application of an acid to neutralize the caustic solution (as in typical 2-part teak cleaners).
By the way, thorough rinsing should be done with clean water.

Last edited by Seaduction; 08-22-2012 at 07:11 PM. Reason: further clarification
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post #7 of 13 Old 08-23-2012
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Re: Black spots on the wood

When ya rinse be sure to flood it with water, not spray it off.

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Bellingham, WA.

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post #8 of 13 Old 08-23-2012
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Re: Black spots on the wood

Quote:
Originally Posted by CharlieCobra View Post
When ya rinse be sure to flood it with water, not spray it off.
That's a new one on me. How come?


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post #9 of 13 Old 08-23-2012
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Re: Black spots on the wood

I assume spraying can splash the bleach places you don't want it. Like canvas. Don't ask how I know.
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post #10 of 13 Old 08-23-2012
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Re: Black spots on the wood

The bleaches penetrate into the pores. Flooding it with water gets it out so it doesn't attack your finish from underneath. Kind of like flushing acid or something out of your eyes. You flood it, not spray it.
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Bellingham, WA.

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