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Old 10-02-2014, 12:33 AM   #1
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CPES Under Varnish

This is one for those who advocate using CPES on bare timber, before applying varnish top-coats. I want to use this system on my teak cockpit doors....in fact I have already taken them back to bare timber, sanded smooth and applied two (2) coats of CPES. The surface is tacky....which I understand is the ideal time to apply the first coat of varnish. But the surface is now also roughened....do I go ahead and apply the varnish and assume I will be able to sand the first varnish coat smooth before applying the 2nd....or should I now wait for the CPES to fully harden, sand it smooth and then start varnishing? Just seems odd to have gone to all the trouble of achieving a super-smooth finish on the bare timber to have CPES roughen it up....

(Have PM'd Marin about this too as I know he was a big advocate of this approach when he was active on the Forum.)

thanks in advance
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Old 10-02-2014, 01:43 AM   #2
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If the CPES isnt fully cured, it will outgas under the varnish. You need to allow it to dry, sand it smooth- lightly- and apply varnish. I don't advocate the use of he stuff myself. I prefer to wet sand with Seafin teak oil to seal the wood, then apply varnish. You can also use 15-20 percent thinner (I like turpentine) for the base coats. This allows deep penetration and much better sealing and adhesion.
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Old 10-02-2014, 04:52 AM   #3
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We sanded the CPES before we added the varnish. I wanted to knock any rough areas, the same I would with any primer/sealer. It sounds like you don't need to.

Here's what CPES says:

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Old 10-02-2014, 04:58 PM   #4
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Aquabelle--- Here is what I do, which I learned from the former owner of Oak Harbor Boatworks, who founded the Grand Banks owners forum.

On bare wood (CPES does nothing over existing finish), I put on one or two coats of CPES, making sure it penetrates as well as it can. As you have observed in your project, this raises the grain and gives a rough-ish surface.

After letting the first CPES treatment cure, I then give the wood a very light finish sanding, just enough to knock down the raised grain. I then put another coat of CPES on.

While this coat is still good and tacky I put on the first coat of finish. We have been using Bristol on the exterior teak on our boat for the last 14 years. Ideally, if the weather and my schedule cooperate, we try to get at least eight coats onto the wood.

So even though the final coat of CPES might raise the grain a bit again, it becomes a non-issue as the coats of finish build up, particulalry in the way we apply the finish coats.

We try to put on three coats of Bristol the first day. We let them cure for a few days, then give it a light finish sanding. We then put on three more coats of Bristol, let them cure, do the final finish sanding to get the surface as smooth as possible, and then apply the final finish coat taking care to get it as smooth as possible in its application.

Unfortuately, being in the rainy, misty Pacific Northwest, my schedule and good weather rarely align to allow us to do a proper finish job. So we put on what we can, and keep the covers on all the time to keep the deterioration rate down until the day comes (in a couple of years) when we will have the time to do a proper job on all the external teak on the boat, which will include removing and rebedding all of it.

When we have been able to get eight or ten coats of Bristol on a piece, we've found that it's good for seven or eight years or sometimes even more in the weather, and longer if we keep covers on the wood when we're not using the boat (or if we're simpy too lazy to take them off when we are using the boat)

We try to put a refresher coat on every four years or so unless the weathering requires a piece to be done sooner.

Everyone has their own favorite way of applying finishes to wood, and there's nothing that says the way we do it is the best way. It's the way we were taught by one of the most experienced GB folks on the planet, so we've stuck to it.
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Old 10-02-2014, 05:16 PM   #5
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Originally Posted by Aquabelle View Post
This is one for those who advocate using CPES on bare timber, before applying varnish top-coats. I want to use this system on my teak cockpit doors....in fact I have already taken them back to bare timber, sanded smooth and applied two (2) coats of CPES. The surface is tacky....which I understand is the ideal time to apply the first coat of varnish. But the surface is now also roughened....do I go ahead and apply the varnish and assume I will be able to sand the first varnish coat smooth before applying the 2nd....or should I now wait for the CPES to fully harden, sand it smooth and then start varnishing? Just seems odd to have gone to all the trouble of achieving a super-smooth finish on the bare timber to have CPES roughen it up....

(Have PM'd Marin about this too as I know he was a big advocate of this approach when he was active on the Forum.)

thanks in advance
Having done this quite a few times.....

1. Let it dry for a week to outgas.
2. Wet sand the epoxy with 150 grit to knock down the fuzz, or coarser grit if you have epoxy that puddled and the surface isn't smooth.
3. Then apply the varnish.

The whole point of this is to prevent wicking of moisture into the wood from dings. The thinned epoxy prevents that migration.
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Old 10-02-2014, 05:26 PM   #6
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Many thanks to all contributors....just the info I needed to push on.
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Old 10-02-2014, 05:27 PM   #7
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The reason for applying the first coat of finish over a still-tacky coat of CPES is that the CPES holds the first coat of finish down like you wouldn't believe, and this goes a long way toward preventing moisture from working its way in under the finish, which no matter how many coats of finish have been applied, will start to lift it.

We originally did not use the finish-over-tacky-CPES technique but let the CPES cure completely before applying the finish.

But we have found, particularly in our damp, rainy weather with the boat outside year-round, that applying the first coat of finish over tacky CPES really adds to the longevity of the finish and goes a long way to preventing moisture from getting under the finish at joints in the wood, which is usually the first penetration point for moisture under the finish.
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Old 10-02-2014, 07:45 PM   #8
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The reason for applying the first coat of finish over a still-tacky coat of CPES is that the CPES holds the first coat of finish down like you wouldn't believe, and this goes a long way toward preventing moisture from working its way in under the finish, which no matter how many coats of finish have been applied, will start to lift it.

We originally did not use the finish-over-tacky-CPES technique but let the CPES cure completely before applying the finish.

But we have found, particularly in our damp, rainy weather with the boat outside year-round, that applying the first coat of finish over tacky CPES really adds to the longevity of the finish and goes a long way to preventing moisture from getting under the finish at joints in the wood, which is usually the first penetration point for moisture under the finish.
In Sydney, it may be a bit different. The outgassing of epoxy is real and varnish really doesn't seem to mix well with it. At least in my experience.
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Old 10-02-2014, 08:06 PM   #9
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Delfin,

I was wondering about that myself. If "out-gassing" is a problem on the first coat under Varnish, or general use of CPES, why / how does Marin get such Fantastic results doing so on his GB? Does it have something to do with the rapid application of multiple coats of Bristol above it?

Far be it from me to question the honorable Marin, but the physics to me does not compute. I would think the CPES would form mini-bubbles in the soft varnish. I could see a case for less than total cure, but not for "still tacky".
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Old 10-02-2014, 08:15 PM   #10
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This from the Rot Doctor:


Subject: CPES (as teak primer)
Date: Mon, 31 Jan 2000

Hi,
I'm refinishing the inside of my Grand Banks. I'm stripping all interior teak down to bare wood. I've purchased some of your CPES and want to put it on all interior teak before varnishing. I have a couple questions for you...
1.) After using CPES on the bare teak, do I need to further prep the wood before applying the first coat of varnish?
No. Apply your varnish 1-2 days after the CPES.
2.) Is there any blush on the wood after applying CPES?
CPES has been carefully formulated to reduce amine blush to the point that it does not effect the bond. There is no prep needed (not even sanding) before applying the varnish.
3.) As with most varnish, the manufacturer recommends two or three thinned coats of varnish (first 25%, second 15%, third 10% for example) before building up additional coats thinned 0-5%. Since CPES seals the wood, and really isn't going to allow the varnish to penetrate the wood anyway, is it still necessary to apply the first two or three thinned coats or can I start with coats thinned 0-5%?
Thanks,
Jim
One coat of CPES performs the function of all three primer coats. Apply the CPES, 1-2 days later start varnishing full strength. If you are planning on staining the wood, do so first, preferably with a water based stain, then CPES and varnish after the stain dries.
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Old 10-02-2014, 08:26 PM   #11
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Delfin,

I was wondering about that myself. If "out-gassing" is a problem on the first coat under Varnish, or general use of CPES, why / how does Marin get such Fantastic results doing so on his GB? Does it have something to do with the rapid application of multiple coats of Bristol above it?

Far be it from me to question the honorable Marin, but the physics to me does not compute. I would think the CPES would form mini-bubbles in the soft varnish. I could see a case for less than total cure, but not for "still tacky".
Bristol is a two part urethane, so my guess is it kicks off and seals the epoxy in a way varnish would not. Either way, adhesion to cured epoxy is going to be as tenacious as you are going to get after wet sanding the surface with 150 grit, so putting the varnish on quickly before the epoxy can cure will not improve that adhesion, IMO.

p.s. I used this technique on a spruce mast on my 36' Cape George cutter and following 9 coats of Schooner varnish, the finish looked like new 6 years later when I sold the boat. The cabin side, cap rails and bow sprit received similar treatment and also held up far better than varnish alone.
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Old 10-02-2014, 08:31 PM   #12
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In Sydney, it may be a bit different. The outgassing of epoxy is real and varnish really doesn't seem to mix well with it. At least in my experience.
Don't know about varnish. We stopped using it 14 years ago and only use Bristol. Bristol and CPES work together beautifully.

However, a number of the owners on the GB forum use varnish over CPES. They, too, apply the first coat of finish over the last, still tacky coat of CPES, and they report the same excellent results as we have with Bristol.

Bob Lowe, the former owner of Oak Harbor Boatworks and the founder of the GB owners forum has promoted the finish-over-tacky-CPES technique for many years. However, he, too, switched to Bristol on his own boat a long time ago, so I don't know if he's had direct experience with varnish over uncured CPES.

We ourselves have never tried varnish over tacky CPES, so I can only pass on what the other GB owners have attested to.

I agree that applying a finish over cured CPES will not improve upon the adhesion of the finish. It is what it is. But appplying the first coat of finish over still-wet CPES in effect "glues" the finish down with more adhesion than one gets from the finish alone.

This has no effect or benefit to the appearance of the finish when the job is complete. What it does is make it harder for moisture to get under that first layer and start lifing the finish.
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Old 10-02-2014, 08:40 PM   #13
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Don't know about varnish. We stopped using it 14 years ago and only use Bristol. Bristol and CPES work together beautifully.

However, a number of the owners on the GB forum use varnish over CPES. They, too, apply the first coat of finish over the last, still tacky coat of CPES, and they report the same excellent results as we have with Bristol.

Bob Lowe, the former owner of Oak Harbor Boatworks and the founder of the GB owners forum has promoted the finish-over-tacky-CPES technique for many years. However, he, too, switched to Bristol on his own boat a long time ago, so I don't know if he's had direct experience with varnish over uncured CPES.

We ourselves have never tried varnish over tacky CPES, so I can only pass on what the other GB owners have attested to.
Like you, my expertise is limited to my experience, which may be insufficient. Thinking back, one reason I let the epoxy cure was because I never could get it flat after application to suit the result I wanted so needed to wet sand it before varnishing and that was facilitated by curing first. Be that as it may, the only argument to applying the top coat over the epoxy before it had fully kicked is to improve adhesion, and I can't see it. For varnish, I can see adhesion being reduced, not improved. Varnish has only lifted for me when applied over wet wood, and the cured epoxy fixes that issue.
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Old 10-02-2014, 08:47 PM   #14
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Originally Posted by Larry M View Post
This from the Rot Doctor:


Subject: CPES (as teak primer)
Date: Mon, 31 Jan 2000

Hi,
I'm refinishing the inside of my Grand Banks. I'm stripping all interior teak down to bare wood. I've purchased some of your CPES and want to put it on all interior teak before varnishing. I have a couple questions for you...
1.) After using CPES on the bare teak, do I need to further prep the wood before applying the first coat of varnish?
No. Apply your varnish 1-2 days after the CPES.
2.) Is there any blush on the wood after applying CPES?
CPES has been carefully formulated to reduce amine blush to the point that it does not effect the bond. There is no prep needed (not even sanding) before applying the varnish.
3.) As with most varnish, the manufacturer recommends two or three thinned coats of varnish (first 25%, second 15%, third 10% for example) before building up additional coats thinned 0-5%. Since CPES seals the wood, and really isn't going to allow the varnish to penetrate the wood anyway, is it still necessary to apply the first two or three thinned coats or can I start with coats thinned 0-5%?
Thanks,
Jim
One coat of CPES performs the function of all three primer coats. Apply the CPES, 1-2 days later start varnishing full strength. If you are planning on staining the wood, do so first, preferably with a water based stain, then CPES and varnish after the stain dries.
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Larry, do you think the word "stain" in the last sentence is a misprint? If you put the stain on first, then the CPES, how do you decide when the "stain" has dried? Am I missing something?
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Old 10-02-2014, 08:48 PM   #15
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Be that as it may, the only argument to applying the top coat over the epoxy before it had fully kicked is to improve adhesion, and I can't see it..
It's like putting glue on top of glue. According to Bob, the first coat of finish "mixes" with the still-wet CPES and as a result there is a tighter bond between that first finish coat and the CPES which of course has soaked into the wood to a degree. So the end effect is the first coat of finish is "bonded" more effectively to the wood than if it was relying solely on its own adhesion properties.

I was skeptical, too, that it would make much difference. But because the trim and joint bedding on our old boat is pretty much shot, we have a real problem with moisture getting under the finish, particularly around joints and seams. When I finally started taking Bob's advice on applying the first coat of finish (Bristol in our case) over still-wet CPES, the problem of moisture getting under the finish at our problem spots was dramatically reduced, even with the fewer-than-ideal number of coats of finish we typically have time to apply before the weather or my work schedule gets in the way.
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Old 10-02-2014, 08:53 PM   #16
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Larry, do you think the word "stain" in the last sentence is a misprint? If you put the stain on first, then the CPES, how do you decide when the "stain" has dried? Am I missing something?
I would think that the directions for the stain would indicate the drying time. If in doubt, give it a few more days. But if one wants to stain the wood for some reason, it obviously has to go down first because once the CPES has been applied, stain won't penetrate the wood cells anymore so it won't work.
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Old 10-02-2014, 11:54 PM   #17
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What 'varnish' do you intend to use over the CPES?

Bristol was available here for a time, although there was a hiccup in supply about a year ago, reportedly due to the death of the founder. But it does look to be still available in the US.
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Old 10-03-2014, 02:27 AM   #18
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The manufacturing of Bristol was taken over by another supplier. It seems as readily available today in this area as it's always been.
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Old 10-03-2014, 09:05 AM   #19
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Larry, do you think the word "stain" in the last sentence is a misprint? If you put the stain on first, then the CPES, how do you decide when the "stain" has dried? Am I missing something?
Carl: I think the order is correct and as Marin says just give the stain time to dry.

We have used CPES on the teak shower grate: applied the CPES as directed, let it dry, lightly sand and then apply multiple coats of varnish. I do thin the satin varnish but only ~5% for better flow characteristics only. The durability of the finish is outstanding. The varnish still wears but the teak does not get wet. Before we used the CPES, with only varnish, water would destroy the finish within a year or so. Now we can go several with only a maintenance coats of varnish. The shower is used twice per day. From what I can tell, the CPES, really does seal the wood and helps prevent moisture from getting into the grain.

The only down side of the CPES, is the dry time: a minimum of 2 days and a maximum of 8 days. Patience is not one of my strong suits.
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Old 10-03-2014, 10:40 AM   #20
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Carl: I think the order is correct and as Marin says just give the stain time to dry.

We have used CPES on the teak shower grate: applied the CPES as directed, let it dry, lightly sand and then apply multiple coats of varnish. I do thin the satin varnish but only ~5% for better flow characteristics only. The durability of the finish is outstanding. The varnish still wears but the teak does not get wet. Before we used the CPES, with only varnish, water would destroy the finish within a year or so. Now we can go several with only a maintenance coats of varnish. The shower is used twice per day. From what I can tell, the CPES, really does seal the wood and helps prevent moisture from getting into the grain.

The only down side of the CPES, is the dry time: a minimum of 2 days and a maximum of 8 days. Patience is not one of my strong suits.
I was just confused because the way the statement is worded, the sequence was stain first, then CPES, then once the stain has dried, varnish. Didn't make sense to me.

A shower grate is an excellent test bed for this technique and you are doing it that same way I have for a long time. Incidentally, I've started using tung oil to increase flowability of the varnish. It doesn't take much and has the downside that it does significantly increase the time for the varnish to dry, but it makes even the stickiest varnish flow and flatten like honey.
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