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Old 04-20-2014, 12:57 PM   #1
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Cleaning black off teak caprail.

I've stripped and begun refinishing the teaks in the cockpit. I'm now about to tackle the cap and handrails forward of the cockpit. There is some water damage and black (mold?) damage near the joints on some areas of the caprail and I am contemplating whether to use the 2 part acid cleaner on these, but am somewhat reluctant. My shipwright friend cautions about over zealous sanding as teak is a soft wood and too much material can be removed, so I want to proceed cautiously.

Can I just apply the cleaner to the affected sections, or will the colour be lighter I. The cleaned areas. The underlying wood is now quite bright already.

How long do I need to let this dry afterward? Product says 2 weeks which is near impossible this time of year in Vancouver.

I intend to follow up,with 2 coats Cetol Natural Teak and 6-8 coats Cetol Marine Gloss.
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Old 04-20-2014, 03:38 PM   #2
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I wonder how deep the black can go?

The book BRIGHTWORK by Rebecca J Whitman offers just about everything that can be done re stripping old finishes. The chemical route offers results but is involved and a bit dangerous. She recommends you seal off every single way fumes can get into a boat before starting.

The five basic methods of removing finishes from wood are:
1. Heat
2. Chemical
3. Dry scraping
4. Acid bleaching
5. Sanding

I have only used 5, 1, and 3.
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Old 04-20-2014, 03:52 PM   #3
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Thanks, but stripping the old finish off isn't the problem. There is a pattern of "black" in the grain proximate to the joint. If the pattern was more random and elsewhere, I wouldn't worry too much about it but it is more obvious as a pattern that follows where two boards join, if you get my meaning. Sorry. Don't have a photo.
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Old 04-20-2014, 03:58 PM   #4
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You will only remove a small amount of teak sanding. To kill the mold spores and bleach the color back I use oxalic acid, which by the way is organic and in spinach, in hot water and let it dry. Then I wipe it off, wash with clean water and sand lightly when it dries. I would do the entire rail so it's even.

You can also wash the bare teak with a strong soap like dishwashing soap. It cleans the teak well. I always clean my teak just before applying the first coat with acetone so the oils in the wood are removed and the first coat of varnish can adhere better. Wear gloves and use white rags. I wipe with clean rags until the rags are not turning brown. You'll be amazed at how long the varnish holds to the teak if you clean it like this first.

I have varnish still on the rails I applied in 2000.
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Old 04-20-2014, 04:02 PM   #5
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You will only remove a small amount of teak sanding. To kill the mold spores and bleach the color back I use oxalic acid, which by the way is organic and in spinach, in hot water and let it dry. Then I wipe it off, wash with clean water and sand lightly when it dries. I would do the entire rail so it's even.

You can also wash the bare teak with a strong soap like dishwashing soap. It cleans the teak well. I always clean my teak just before applying the first coat with acetone so the oils in the wood are removed and the first coat of varnish can adhere better. Wear gloves and use white rags. I wipe with clean rags until the rags are not turning brown. You'll be amazed at how long the varnish holds to the teak if you clean it like this first.

I have varnish still on the rails I applied in 2000.
Excellent advice.
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Old 04-20-2014, 05:42 PM   #6
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So Capthead:how long would you let the wood dry after this treatment?
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Old 04-20-2014, 05:53 PM   #7
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I also have a couple of spots on my cap rail where I had metal clips for my ladder lag-bolted down. I'm ready to refinish and will probably re-attach the same fittings. Still, I'd like to learn how to remove the black spots, even if they are out of sight. Still hesitant.
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Old 04-20-2014, 05:55 PM   #8
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The MEK or Acetone cleaning can be varnished over as soon as you're done. Say you start at the bow and wipe to the transom, go back with a Scotchbrite to clean off any lint fuzz and you can start with a thinned first coat of varnish.

If it's a soap wash, I'd do that before the Acetone wipe and let the water dry a few hours.
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Old 04-20-2014, 05:59 PM   #9
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Black spots can be bleached with oxalic acid. If it's difficult, wet the spot then rub the powder on the spot and brush it in lightly with a wet brush. Let it dry and wipe it off. If it isn't gone, repeat.

The 2 part cleaners are very harsh and will eat the wood, my experience anyway. I like oxalic and have had great results with it.
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Old 04-20-2014, 07:46 PM   #10
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I scrub my teak with Cascade dishwashing detergent. Works great
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Old 04-21-2014, 10:13 AM   #11
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I scrub my teak with Cascade dishwashing detergent. Works great
Exactly what I said earlier. Dishwashing soap works great. Oxalic acid gets the color back and even.
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Old 04-21-2014, 10:59 AM   #12
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Capthead,
Don't mean to be disrespectful but Rebecca Whittman Who wrote a very well known and comprehensive book on finishing wood called "Brightwork .. The Art of Finishing Wood" says that the percieved need to get the oil out of teak before coating is "hogwash".

I have very successful experience w varnishing extremely oily teak too to prove she's right. BUT ... others have experienced good success but removing some or most of the oil first. So I'm led to believe that it dosn't make any difference.

However in the book she does not discuss anything but oil based finishes. So de-oiling teak may be the thing to do when contemplating polyurethane, epoxy or other non oil based finishes.
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Old 04-25-2014, 12:41 AM   #13
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Drying of teak is usually quite quick. Teak, compared to many woods is quite resistant to water absorbtion due to the oily nature.
Any water in the joints will take longer for the water to evaporate out.
I've started varnishing within hours after a washdown. If the sun and a light breeze is out even faster.
You just have to cautious about joints or around fittings and hardware where some water can be trapped.
I also use alcohol to wipe down dew covered varnish after taking the bulk dew off with a chamois or microfibre cloth. The alcohol will pick up small quantities of moisture and take it away and then the alcohol will flash off.

I too do not worry about deoiling the wood. I do thin about 20-25% the first coat on raw wood.
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Old 04-25-2014, 06:32 AM   #14
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Capthead,
Don't mean to be disrespectful but Rebecca Whittman Who wrote a very well known and comprehensive book on finishing wood called "Brightwork .. The Art of Finishing Wood" says that the percieved need to get the oil out of teak before coating is "hogwash".
I think it's good to remember Ms. Whittman did the vast majority of her brightwork in the PNW. So what worked there may not hold true for other climates. While I have not seen it often, I have seen varnish lift off of the wood. So a wipe down with alcohol or acetone certainly can't hurt.

I thin my first coats by 50% to get deep penetration into the wood. And brush two or three of them on one right after the other.

As to how well other finishes adhere to teak, epoxy naturally adheres perhaps the best of all. It s an adhesive after all.

As to the black stains at joints. Good advice has been given on how to get rid of them. But I have seen them go deep from time to time where you just have to learn to live with them. Or you would need to take off so much wood to remove them that you could end up with a deep low spot in the wood at the seam that would require feathering out of the wood and could still leave a dip in the rail.

Some times it's best to think of the little imperfections in the wood on an older working boat as adding character to the wood work and the varnish job.
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Old 04-29-2014, 10:51 AM   #15
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The work continues! I have already stripped the teaks along the caprail, sides and transom in the cockpit and have 2 coats natural teak and 2 coats marine gloss (cetol). I will try and get another 6-8 coats of marine gloss on. Now stripping the caprail along the sides. I have used the 2 step teak cleaner (carefully--I didn't go nuts with it) just where the mold was evident. Evil stuff, but it seemed to work and didn't take off too much wood. It has removed much of the black. The old finish sure is thick and difficult to remove in spots. Using the heat gun and gentle putty knife action. Then I use a cabinet scrapper (card scrapper) with a burr on it to remove the stubborn stuff. This card scrapper works really well and reduces sanding significantly.
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Old 04-29-2014, 11:41 AM   #16
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I have used the two part Semco on the black moldy stuff .It is wicked but it works. Cabinet scrapper is a good idea.It can remove material fast and give you a good finish . You will have continully refurbish the burr .
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Old 04-29-2014, 12:10 PM   #17
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Greetings,
Regarding the Cetol Marine Gloss. I have already stripped the cap rails and applied 2 coats of Cetol regular finish. I am of two minds on whether or not to finish with several coats of Gloss. The Admiral, who is usually and will in the future be in charge of this task wants to know if maintenance of a gloss finish is more work than the regular. She is quite happy with the regular finish but I sort of like the "depth" of the gloss having already done the screen door which is a stand alone item. So, the question is to gloss or not? How does the gloss last in comparison to the regular? Help!
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Old 04-29-2014, 01:12 PM   #18
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Someone told me gloss reflects the sun's rays and lasts longer than dull finishes that absorb the UV.

I don't have any experience with dull finishes. That is what I was told and I'm sticking with it.
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Old 04-29-2014, 01:30 PM   #19
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Greetings,
Regarding the Cetol Marine Gloss....So, the question is to gloss or not? How does the gloss last in comparison to the regular? Help!
The Cetol Gloss is a harder more durable finish than the Natural or the Light which has UV protection in it. When we were in Mexico, we would only get about 9 months out of the Light which was disappointing. Later, we reapplied the Light (3 coats) and then 3 coats of the Gloss. A year later it looked good. Your mileage may differ but I think the Light or Natural, over-coated with the gloss, is the way to go.
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Old 04-29-2014, 01:32 PM   #20
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RT: as per your question, this fellows blog is quite interesting. He finishes 10 coats of regular varnish with 2 coats of cetol high gloss because he feels it is more durable.

http://varnishteak.blogspot.ca

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