Arresting the demise of teak

[John R.]

Thanks Larry for making your explanation. I agree we are talking about a thermal response within the wood which occurs in all woods, teak or no teak. The only major difference is being that the oily resins within teak are either being "pushed" (pressure) to the surface as you imply or are simply leaching like sap leaches from a maple tree when cut or injured.

With teak, warm temperatures have the typical effect of expanding pores like in any wood and that simply allows the resins to move easier and in greater quantity. Air in combination with heat from the sun and its UV rays all contribute to the drying out process. I believe the eventual loss of adhesion of a topcoat finish is only marginally due to this resin flow to the surface, the speed of which is affected by temperature. Any place in the wood the resins have been depleted allows for the onset of rot as long as oxygen, dampness and warmth exists, the rot spores will proliferate and the onset of the fungus will begin. End grain being especially susceptible.

Loss of topcoat adhesion can be greatly minimized by use of a penetrating finish rather than one that simply lies on top. It seems great success has been made with newer penetrating finishes ( low viscosity urethanes and epoxies) to dramatically reduce the flows of the teak resins to the surface no matter what the thermal situation. Although rapid changes from cold to warm temperatures will often result in air expelling from the substrate that can compromise a finish adhesion. Is that pressure? I don't know. I would call it breathing. If you come across more information on "pressure" please post it as it would be of benefit in gaining a thorough understanding of what takes place in a wood substrate.

Do I understand you correctly......do you have solid teak bulkheads in your 30? Our 30 I believe is all veneered ply bulkheads like most boats, just double layer 3/4" ply with a teak veneer both sides. I'd hate to hear the price of a 1-1/2" solid teak bulkhead plus I don't think the strength would be anywhere near that of plywood.

Well, I can try to explain this effect. I do not have any textual sources for you other than references to this effect in a multitude of finishing articles and books over the years.
Here is what I believe is close to what happens:

Natural teak is absolutely filled with oils, which protect the surface of the wood fiber from water intrusion, as well as insects. Allowing that surface to be exposed to UV rays, causes a drying out of that surface fiber, which then wicks the oils from underneath it towards the surface. Aiding this is an internal pressure, generated by changes in temperature.Higher temps would cause an increase in this pressure <must be a very small pressure>, which will force more oils into the depleted area, where they are oxidized by UV rays. Once UV rays have dried the teak out sufficiently, water intrusion starts to occur, which will allow the chemical changes that are a process of rotting. The wood will warp, and crack as it wants to, following the grain.

NOw during this process, the wood turns nicely grey, and makes a great non-skid surface for us to walk on. Left alone, the rotting process will allow mildew to grow with black spots spreading horizontally and vertically into the woods fiber..and we look at it and say it needs to be cleaned and 'brightened', a process that uses bleach to kill the mildew and rot. Then the wood returns to it's familiar tan coloration for a period.

Cetoling at this point will cover that surface with a porous seal. The seal is good because water never reaches the wood fiber, and the UV spectrum is prevented from reaching the wood fiber, so no oils are lost to oxidation and the wood remains stable.

That is about as good an explantion as I acan come up with this morning. I will research this a bit more and report back with what I can find out. Seems it is a continual problem with any teak on boats.

I priced out the bulkhead on my CD30..as if I was going to replace it. Guess what? You cannot. I could not find a single source of teak that would provide a piece such as we have on our boats now. You would have to settle for another species, or a laminated application over marine ply. There will come a time, perhaps we are there now even, when teak will just not be included on boats at any price within reason. It would seem that this is a valuable wood, and worth caring for properly.

Does this help?

Cheers!

Larry DeMers
s/v DeLaMer
Cape Dory 30

What I have done on other boats that wanted a varnish finish was to clean as others have described well, then use a teak brightener,really just a bleach preparation (which is all I would use now if doing it).
This will uniformly lighten the wood, towards the light tan color usually..or slightly darker if you limit the chlorine exposure. Rince exceedingly well, using fresh water, a soft brush raked with the grain, then do it again. Allow to dry completely..overnight or longer. Then go to it with the finish of your choice.
I have to say that I have seen some of the most breathtaking varnished finishes on teak bowsprits for instance. The grain just jumps out at you and you feel like treating the piece like a coffee table or something! The boat was heading for the Caribbean, then up and around to Scotland..from Superior. The guy had 12 coats of varnish built up over the winter (he took the bow sprit off and brought the whole darn thing home!)..now that is a varnish nut!
But this is nutz from any practical standpoint you care to use. A bowsprit gets used hard, and I argue that that kind of finish belongs below decks or on protected wood, that sees light service.

Onwards!

Cheers!

Larry DeMers
s/v DeLaMer

Someone in this thread mentioned that teak does not rot and unfortunately that is not true. Under the right circumstances teak will rot just like any other wood just not as easily. It is certainly highly resistant under the right conditions but not rot proof. It can and will easily rot around seams of bungs covering screws, and at other types of seams and joints if left to weather the elements. Especially in warm damp areas such as in the south,ie: Florida.

Larry, could you please offer more details about the "pressure" in teak and how that lifts a finish? The resins in the wood certainly migrate to the surface as does moisture in any wood and that resin migration certainly compromises adhesion of a finish in time. I've simply never heard of a "pressure" per se unless you are speaking of trapped air during the application of a finish. If you can point to a source of additional information on that point I'd like to read more about it. Thanks

[Bob C.]

I wouldn't worry about the "demise" of your teak. The primary reason for using teak for trim to my way of thinking is that it does not require varnishing or Cetol et al. It does not rot though it is susceptible to mildew which is easy to control. It naturally weathers to a light gray however with light fairly frequent scrubbing with soap and water will maintain the usual teak coloration. You don't see the Navy varnishing or "cetoling" their teak decks. They "holy stone" them if that's the right expression. If you want varnished trim replace your teak with mahagony! I've been looking at Tys lately (to buy) and I can tell you that the Tys with varnished trim don't pass muster. My first thought is that if I did buy one of these the first thing to be done would be to strip all varnish from teak. I don't have experience with teak "oils" but that sounds a lot more sensible than any kind of "film"

This spring I purchased a '77 Ty. Great boat and I love to sail it more then work on it. I had an inspection before I purchased (and am very glad that I did) so I went into this knowing I have some work ahead before I get "Vahevala" into "Ship Shape and Bristol fashion". From the inspection I have three issues. 1) weeping where the keel stub mates to the ballast - this has been fixed by professionals. 2) Deck needs new paint. 3) Teak is in fair shape. Very weathered but can be restored.

I have a three year plan which follows the list above. So next year I want to paint the deck and finally get to the teak end next year as a winter project.

My question: What can I do to the teak to keep it from getting any worse. Right now it is the grey, weathered and worn look with deep grain texture. Some cracking is beginning.

Thanks in advance for any suggestions.

John B.
Ty "Vahevala"

Cha62759@traverse.com

[Don Craig]

There's a lot of misinformation going around on this particular subject. You are quite correct that teak does not require any finish at all; it can be left bare and will remain sound longer than the life of just about any boat. I said in an earlier post that teak will not rot, and was contradicted. I was referring to teak trim, the subject at hand. I've been around boats for decades, and I have never seen one piece of rotted topside teak trim, finished or not. Improper scrubbing of teak does much more damage to trim and decks than the natural elements. Bristle brushes, power washers, or any kind of abrasive pads worked WITH the grain, should NEVER be used on teak. All these methods open and excavate the grain, exposing the wood to mildew and grime. Frequent rinsing with salt water, or fresh otherwise, and occasional light washing with mild dish detergent in water and a SOFT (white) nylon tile scrubber worked in a circular motion ACROSS the grain, will keep your bare teak looking great. Long neglected bare teak may be restored with chemical treatments like Teak Wonder or Te-Ka.

I can tell you from personal experience and that of others: Teak takes varnish beautifully. The wood must be prepared properly, and the varnish applied properly. Yes, it does take more time than Cetol. But varnished teak trim conscientiously maintained will wear its original foundation for many years. Ask a professional yacht finisher in a major boating center. Talk about oil seepage from within the wood and "internal pressures" causing varnish finishes to fail has no basis in fact. The failures come from neglect, or lack of knowledge in the original application. (By the way, mahogany MUST be protected by a finish. Unlike teak, it cannot be left bare.)

I don't consider oil a satisfactory finish for exterior teak (it can be a great finish below decks). It provides only fleeting protection from the elements, is a magnet for dirt, and must be renewed more often than either varnish or Cetol to continue looking good. It's high maintenance.

I still think the best "look" for a classic boat like a Cape Dory is a combination of bare teak (toe and rub rails?), and varnished trim. Cetol requires less skill and maintenance time, but even the best Cetol finish can't compare with the look of a quality varnish job. Just one partisan's opinion. For those who really want to understand this subject, I refer them again to Rebecca Wittman's book "Brightwork: The Art of Finishing Wood."

I wouldn't worry about the "demise" of your teak. The primary reason for using teak for trim to my way of thinking is that it does not require varnishing or Cetol et al. It does not rot though it is susceptible to mildew which is easy to control. It naturally weathers to a light gray however with light fairly frequent scrubbing with soap and water will maintain the usual teak coloration. You don't see the Navy varnishing or "cetoling" their teak decks. They "holy stone" them if that's the right expression. If you want varnished trim replace your teak with mahagony! I've been looking at Tys lately (to buy) and I can tell you that the Tys with varnished trim don't pass muster. My first thought is that if I did buy one of these the first thing to be done would be to strip all varnish from teak. I don't have experience with teak "oils" but that sounds a lot more sensible than any kind of "film"

This spring I purchased a '77 Ty. Great boat and I love to sail it more then work on it. I had an inspection before I purchased (and am very glad that I did) so I went into this knowing I have some work ahead before I get "Vahevala" into "Ship Shape and Bristol fashion". From the inspection I have three issues. 1) weeping where the keel stub mates to the ballast - this has been fixed by professionals. 2) Deck needs new paint. 3) Teak is in fair shape. Very weathered but can be restored.

I have a three year plan which follows the list above. So next year I want to paint the deck and finally get to the teak end next year as a winter project.

My question: What can I do to the teak to keep it from getting any worse. Right now it is the grey, weathered and worn look with deep grain texture. Some cracking is beginning.

Thanks in advance for any suggestions.

John B.
Ty "Vahevala"