View Full Version : Silicone vs polysulfide based caulking for teak decks?

Dana Marlin
07-15-2011, 12:01 PM
I am about to re-caulk my teak decks here in El Salvador and have found a source of Silicone based caulking (Maritim); however, I had always heard that Polysulfide caulking was the thing to use. What's the scoup? Anyone have any experience with the silicone based variety?


07-15-2011, 12:23 PM
Dana,is this on your Tahiti? interesting question.....i try to avoid anything silicone.....i have only used polysulfide for bedding things like ports and deck fittings,as its always possible to remove the item at some point in the future,so im not sure how thats going to stick in your caulking seams,always used sika-flex or jefferies marine glue for that purpose. Cant say i have looked for or come across a silicone based caulk for decks....... i kinda stick with stuff i know works..... Cheers

Jay Greer
07-15-2011, 12:51 PM
One consideration is: are your deck seams V grooved and caulked with cotton? Or, are they square seamed and dry abutted? In the case of a Ved seam that is caulked, paying the seam with Jefferies Marine Glue will be the most lasting approach and should keep your decks tight for forty or more years. If the seams are square and not cotton caulked then one of the current air curing or catalyzed rubber compounds is your best bet. Unfortunatly the rubber seam compounds do have a tendancy to pull away from the sides of the seams from time to time making the concept of a tight deck a bit iffy. In any case, the sides of the seams should be made as clean as possible and primed, if required, with that which is recommended by the mfg. If the seams do not reef clean, a side rabbet plane set extra fine will be a great aid.
Primer for Jefferie's Marine Glue is a quite simple thin mixture of turpentine and a bit of bee's wax which, will insure adhesion.

Dana Marlin
07-15-2011, 01:21 PM
Thanks guys! Yes this is for Melita. The seams are square and the old caulking has pulled away from the teak quite badly. The problem is here in El Salv my choices are limited. I can either use this Maritim silicone based stuff which says on the tube that it sticks very well to teak. My other option is to order a case (too much for my job) of Boatlife life-caulk which is one part but polysulfide based. The stuff runs about $25 a tube - which on a cruising budget is pretty hefty. I really appreciate all the help.

Jay Greer
07-15-2011, 07:03 PM
Dana, If your "Melita" is the double ender with the name carved into the bulwark, I am the guy who did the carving.
If "Weatherban" 101 by 3M a one part polysulfide is still available, it will do a good job for you.

07-15-2011, 08:50 PM
I have two conflicting opinions.
In general, Silicones in any form are a bad idea.
The Teak Decking Systems SIS 440 is a silicone based teak seam caulk which I have liked and which has been favorably reviewed.
I don't expect this helped.

Lew Barrett
07-15-2011, 10:02 PM

If I understand, TDS is not silicone based, but uses silicone as a release (flow?) agent. In any case, it can be overcoated, which is the point I care to make.

07-15-2011, 10:35 PM
I find reference to 'silane' in the SIS-440 docs, but I'm way over my head.
I withdraw the suggestion that it's anything like the silicone goops we've all come to hate.

Dana Marlin
07-16-2011, 12:35 PM
Well I was reading Boatlife's description of their Silicone based caulking (they have one too) and they state that it is a "revolutionary new caulking system" with improvements over the polysulfide based systems and that it adheres "tenaciously" to teak. Anyway, having bought a few tubes I am now commited to using it so I shall review it once I learn something first-hand.

Thanks for the help again

mike hanyi
07-16-2011, 12:41 PM
the silicone stuff is so soft that the edges of the teak will split, your varnish work will never be the same,full of fisheyes, you will never ever decontaminate your boat from the silicone other then complete deck replacement.

the Fife 12mr VANITY has silicone based deck caulking- it is a very big problem.

even roofing caulking is better.

07-17-2011, 07:56 AM
Good luck with it Dana and keep us informed how it works out,i expect it will work well short term.

Mike makes a good point about silicone and surface contamination,to which i absolutely agree,howver in my case its more like silicone based sprays such as WD40,absolutely banned from being used anywhere near my paint/varnish area. Bit off topic,but i recall spraying a 5ton bobcat digger,had it all prepped and primered and a guy came along to sort out a wiring issue;after applying the finish gloss,fish eyes were everywhere,and still returned after TWICE stripping off and washing down with thinners.Chatting with the guy after he said he had been spraying WD around to free up some fastenings and to polish the inside of the cab!!! Apparently there is a chemical you can buy especially for removing silicone based contaminants, most auto body spray shops should have some handy.

Dana Marlin
07-17-2011, 06:15 PM
Thanks for the info on the silicone. I seem to have gotten off to a bad start anyway. Having applied 3 tubes of the stuff to half my foredeck I ran out and within a couple of hours was overtaken by a rain squall of biblical proportions! The next day most of the seams I had filled when dry were oozing water. I cleaned up the excess silicone later in the day after all had dried but found it was very soft and didn't seem to be holding to the wood well at all. I am going to reef it all out and replace it with some polysulfide goop when I can order some. Lessons learned at expense sting a bit deeper...

Jay Greer
07-18-2011, 09:19 AM
Well at least you now know what works and what doesn't. Eventually you may be asked to comment on what to use for a similar job and will be rewarded by the questioner doing just the opposite.
One little known fact is that L. Francis Herreshoff had a favorite comment that he would save for special occasions such as this which was; "Don't listen to me. I don't know anything about boats."

Lew Barrett
07-18-2011, 09:59 AM
Look into Teak Deck Systems. (http://www.teakdecking.com/) Jim Conlin and I have discussed it in this thread and it has met with good success in the last years. I used it on my fir decks three years ago with very satisfactory results.

07-18-2011, 07:39 PM
even roofing caulking is better.

your right

PL premium Polyurethane Black roof and flashing sealer.
very rubbery and sticks and stays well and is sandable.

cheap compared to that polysulfide. at about $5 a tube.

Dana Marlin
07-19-2011, 06:40 PM
that polyurethane roofing sealant sounds like the best fix. I wonder if I can find that here in El Salvador. Thanks for that. I can't get TDS here unfortunately.

Jay Greer
07-20-2011, 08:02 PM
Another excellent deck seam comound that has a great track record is "Detco",a two part polysulfide product that hangs onto seam edges with incredible tennacity. It was formaly known as Detco Grove Seam Compound. We once used this product on the decks of the 78' 1969 Transpact Ketch "Mir". "Mir" was dismasted in a freak knockdown just 400 yds short of crossing the finish line. The crew had the presence of mind to cut the main mast free and sail the boat backwards under the mizzen spinnaker across the finish line. My pal Tom Hazlett remembers that day well as he was among the first to grab the weather rail as the boat broached and lead the clearing party to free "Mir" from her main mast and main sail drogue.

Oh yes, the "Detco" payed seams performed perfectly without a single leak! We did discover that a drop or two of fresh water in the two part gallon mix causes the product to kick overnight. Great Stuff!
Transpac info on "Mir" here.

07-20-2011, 08:58 PM
I've used Detco for 23 years on Olinka , It's a pain , but I like the way it looks , and feels , cuts and sands . The only silicon I use on the boat is O rings .

Jay Greer
07-20-2011, 09:07 PM
It may be a pain to use, but "Olinka" looks great!

07-20-2011, 09:26 PM
thanks :) and when you going sailing with us :)

07-20-2011, 10:23 PM
Gents, Been down the polysulphide road, didnt like it. Been down the Detco road ( first job in a boatyard, reefing out a batch of failed product, on a 60" Swan....) lasts better, but...Can't say that I would give up the toughness, tenacity, speed and ease of working of the TDS product...As to the concept of piping a dozen cases of some hopeful Home Depot experimental product, that just gives me a bad shiver down my spine... BT

Lucky Luke
07-20-2011, 10:27 PM
Silicon for deck seams....:rolleyes:.....NO!

I remember a long discussion here about polyurethanes vs polysulfides a long time ago where the very regretted "The Chemist" (R.I.P.), an extremely knowledgeable and helpful person that many here will remember but many newer members not know, did explain why the industry turned towards polyurethanes, mainly because of...profitability!!! He also explained lengthily the differences between these two families of products. A very informative thread if someone would mind digging it out!

From my experience and not dictated by economic reasons, I have a great preference for "thiokol" based polysulfides, although reckoning that they are still far from being the ideal stuff we all dream of. The good old thiokol effectively adheres to wood, and moreover to old wood, even when deck seams had previously been "paid" with Jeffry's glue or other tar based compound.

Just a little language correction there, if you guys don't mind: I said paid, which is what we called pouring the stuff in the seams after they had been caulked with oakum + cotton. Even when no previous caulking (and not "corking" and other ignominious appellations!) had been done like in modern "teak decking" - which, to speak correctly once again, should be called "teak laying": I mean laid on plywood - we should not call this caulking. Filling the seams or whatever one likes, but not caulking. Hey: I am a French speaker! I am not the one who should be correcting nautical language digressions there, OK?

This being said, polyurethanes, like (expensive!) Sikaflex 290 DC are good products, but only to be used on brand new decking, teak being well de-greased, properly primed, with a bond-breaker at the bottom of square-shaped seams. There again, since I am in a rant mood: do you know what these @)$%^&@ commercials of Sikaflex recommend now?: to cancel the use of a bond breaker and open the seam all the way down to the (also Sika) flexible glue that has been used to glue down the teak! Like this, you just buy twice as much of their stuff!!! Grrrrrrr!

However, whether on new or old decking, Thiokol beats Sika and other similar products. These polyurethanes, even used as recommended, with careful primer application, do part from the teak along the edges of the seams after years. Thiokol tends to open in the center of the seam after some years, but then one just needs to clean up that "crack" (a cutter works fine) and fill up with thiokol again, in a somehow similar fashion as when repairing Jeffry's paid seams. Of course, nothing will beat this oldie butt goodie as far as ease of repair is concerned as simply running a hot iron does instant repair, even under the rain! With polyurethane: one has to re-open the seam entirely.

The Detco's two part thiokol based polysulfide (or any similar product one may know about) is defiinitely what I would prefer amongst any other.

For who does not want all the fuss associated with mixing of this product, the black mess that one gets no matter how careful, there appears another alternative which like the M1 by ChemLink. Cheap stuff too, much less than Sika! This particular one has been recommended to me by a very well known American boat builder: John Steele, of Covey Island boatbuilding. There are lots of similar products used for construction (TDS, Fixtech may be some of them? Not distributed here anyway.), and I must say that their performance seems astonishing (and very easy to use). I have not personally used them for teak deck seams but would take John's word on that matter!

Now: your choice, gentlemen, but mine been done for a long time: thiokol, till something really beats it.

Lucky Luke
07-20-2011, 10:30 PM
It may be a pain to use, but "Olinka" looks great!

Olinka looks great: that's definitely what I would wholeheartedly agree upon ! :)