Alternatives to clear penetrating epoxy?

[johnw]

Well, I've got some CEPS left over from Black Swan, so I'll probably use it on the boat, but I'd sure like to know what smells so awful about it. Is it toluene, or tree-like resins, or what?

[johnw]

I skimmed the West advisory linked to above, and one thing occurred to me. They said it didn't matter how far the epoxy penetrated, only the permability of the barrier mattered. I have very little experience with epoxy, but I have seen a lot of dings in varnish turn into a variety of white or black scars in the wood, requiring stripping, sanding, bleaching staining etc. to get a uniform surface to reseal with whatever.

It seems to me that the more you can get the epoxy to soak into the wood, subject to the wear and tear of the real world, the better protected the wood will be, and that a few mills of the best goop in the word over a relatively soft wood don't count for **** when a tired old guy is getting klutzy deploying the anchor, unstepping the mast or whatever.

Any thoughts from the experts?

Allan

This is why I don't trust the comparisons between penetrating epoxy and an unthinned epoxy barrier. I think they are testing what their product is good at, rather than what the competing product is intended for.

[Eric Hvalsoe]

I'm not a chemist either. I think toulene is the active solvent at least in the cold weather version of restore it (smiths), that's why it smells the way it smells, why it flashes off as fast as it does. Which is sometimes what I'm looking for. In that case, really, how deeply could it be penetrating? I tend to think of solvents across an arc of volitiity - the higher the volitility, the stinkier, the sooner they flash off, the faster the cure. And then there is alchohal, mmm.

One thing I find Smiths not to be, is rubbery. Now the base coat of Tuf Shield (also stinky) is rubbery. I just used Restore It AKA Smiths AKA cpes today - for some protection with a quick seal on a tiller - a couple of hours later I wet sanded teak oil over it. I was in a hurry. I was not looking for a high build up or a bristol finish. But it still looks pretty sharp. Spose I could have used old salem - but not that old can left over in the paint locker.

I don't think Old Salem is as 'hard' or as tough as CPES or other epoxy variants. In fact it is not particularly thin, and should not be thinned, but it seems to bond well to bare would. If you are in fact trying to fill the grain on the way to a good looking painted or varnished surface, old salem will build a hell of a lot faster than cpes, it is entirely possible in the right conditions to apply four or more coats of old salem in a day. Yes it is used to seal plywood. I don't argue that tweaked epoxy resin can also be used as the 'sealer' coat - best if applied as a flow coat on horizontal surfaces.

One thing John, is that I'm not sure how well old salem will cure over epoxied surfaces and joints, that sort of thing. It might cure differently or much more slowly than over bare wood.

[willin woodworks]

Paul G. states very clearly that he has not tried CPES. With all due respect; if you've never used it how do you know how well it works compared to your home brew?

Read the MSDS for CPES and then compare that to the MSDS for MEK, toluene and xylene. MEK is about as harmful and toxic a substance as you can legally purchase. I would not under any circumstances allow it in my shop. Toluene and xylene are moderately less tixic but still require the use of respirators. Nasty stuff no matter how you slice it.

I was pretty skeptical when I bought my first batch from Smith's but I can tell you that it works and it works better than thinned epoxy which I have tried a number of times with little and limited success.

[Eric Hvalsoe]

Old Salem (or something similiar like Interlux 1026, but I prefer OS) when I can
Smith's when I must

[Paul G.]

Paul G. states very clearly that he has not tried CPES. With all due respect; if you've never used it how do you know how well it works compared to your home brew?

Read the MSDS for CPES and then compare that to the MSDS for MEK, toluene and xylene. MEK is about as harmful and toxic a substance as you can legally purchase. I would not under any circumstances allow it in my shop. Toluene and xylene are moderately less tixic but still require the use of respirators. Nasty stuff no matter how you slice it.

I was pretty skeptical when I bought my first batch from Smith's but I can tell you that it works and it works better than thinned epoxy which I have tried a number of times with little and limited success.

What we are discussing is solvent thinned epoxy not ultra low viscosity epoxy with 100% solids CPES has "Volatile Organic Content (VOC) mixed: 675 g/l" in other word its 67.5% thinners or 32.5% epoxy solids.

Those thinners for the bulk are;

Naptha
Xylene
Toluene
Iso propyl alcohol

plus many additional minor solvents. Its an expensive way to buy thinners. I'm prepared to accept it penetrates better than my 10-20 percent home brew but I think if I thinned my epoxy to to 67.5% solvent I'll bet it penetrates equally well. But the real question is what does it do that neat epoxy wont? One advantage of slightly thinning epoxy is that it doesnt pool and leaves the wood surface dry and non glossy. My experience has been that it is a good primer but I wonder how much of that is a feel good factor as decent thinned paint primer would do the same thing?

No thinned epoxy is completely waterproof unless it is overcoated and the purpose of epoxy sealing is to reduce moisture level changes to below 3 or 4 % ( approx)

So your comment "that it works" means what? Does it make wood waterproof, restore its strength or is it a good primer? If the main use is as a primer and you insist on using thinned epoxy, then my solution is equally as good. The reason is that it does not matter how deep you go with the "penetration" its the surface barrier coat that is the important thing. Water tries to get in from the outside.

[Tom Painter]

I've never been to a CPES tent revival so I'm a little skeptical that it is anything other than a cleverly thinned epoxy. Whether or not to entomb boats in epoxy is an ongoing almost religious argument. There are many examples of long lived boats so treated and not. There are about an equal number of "professionals" who advocate epoxy coating and not. In the end, I suppose, boats seem to last about as long as the owner cares for them...

[Paul G.]

Putting it bluntly, I would say that CPES is faith based as opposed to evidence based. Any popcorn in that revival tent!

[Peter Malcolm Jardine]

Whatever happened to the hot linseed and turps mix? The old method was to warm this stuff up a fair bit, (carefully mind you) and then whitewash brush it into the hull until it wouldn't take anymore.

The other one is copper napthenate, which is Pentox. It comes in clear form as well as green. You use a turkey baster and squirt it in to all parts of the bilge by the gallon.

[Paul G.]

Well, I've got some CEPS left over from Black Swan, so I'll probably use it on the boat, but I'd sure like to know what smells so awful about it. Is it toluene, or tree-like resins, or what?

The smell is a very toxic mix of thinners, remember the bulk of the 2/3rds solvents are common cheap thinners like xylene and toluene.

[Peter Malcolm Jardine]

One part of this discussion is what result are you looking for? Do you want a sealer? Do you want a primer? Do you want a biocide. CPES has it's place, but it isn't the only sealer, and it is not a biocide.

[Paul G.]

Peter my 1945 carvel boat was saturated in red lead copper napthenate and god knows what paint on poison. It lasted as well as the fresh water did not get in! I think the older methods were and are absolutely fine provided there is regular maintenance.

As I understand it the OP was asking about coating ply. Because of the thin layer and glueline whatever epoxy is only going so far. To reduce checking I think the best way it to pay for better plywood and save on the epoxy. End grain should be sealed with epoxy though

Here is a post from a respected boat design forums member Paul Ricelli

1 - Penetrating epoxies (CPES, etc.) do penetrate wood (so does lots of stuff).
2 - Penetrating epoxies do leave behind a coating, within the cellular structure of the wood.
3 - Penetrating epoxies do limit the amount of moisture vapor mitigation into surrounding substrates.
4 - Penetrating epoxies can be used to control moisture content in wood.
5 - Penetrating epoxies are not a very effective "sealant".
6 - Penetrating epoxies are an effective wood primer, under paint.
7 - Dan Dannenberg and the like minded.

Okay, now Richard and others are bunching up their panties. Maybe partly because they haven't seen my logo in a while and partly from the statements in the second paragraph. The second paragraph is completely true, tests have plainly born this out, the debate has been over for some time, but . . .

1 - Testing has shown that one; the addition of solvents does help epoxy resin penetrate wood and two; that this particular trait isn't necessary, nor desirable for a good waterproof seal. In fact, testing has shown that the amount of penetration into wood doesn't have anything to do with the ability of a product to make something waterproof. What has been found from testing is, it's all about the quality of the coating employed, not how far it's penetrated into wood.

2 - When a penetrating epoxy is applied, it eventually leaves a coating of plastic within the wood structure. Because of the reactive diluents and modifiers used in most penetrating epoxy formulations (their big failing point BTW) are grotesquely unable to offer moisture vapor ingress protection, though they can slow it a little, depending on application technique.

3 - Since we've gotten to it, these epoxy types can be employed with other products to effectively prevent moisture vapor penetration (the real goal of waterproofing). Interestingly enough the usual "other" products are epoxies with much higher, preferably 100% solids content after cure. The amount of moisture vapor ingress a penetrating epoxy can resist, is purely subject to the amount of solids in the final results of one's effort. In other words, one coat of CPES really doesn't do much, but several can be considerably better.

4 - There are occasions where penetrating epoxies can be employed with good success. This once, not so long ago was on just about everything imaginable, but in recent years has diminished considerably. Some times the "hot on hot" method can't be employed, so a vehicle penetration might be considered (though a non-reactive modifier is a much better choice). This is when a penetrating epoxy should be considered. Other instances may include partial restoration of highly damaged material for molding, sampling or as a fore runner to restoration. I've used penetrating epoxies to hold damage at a constant, until I could get at the cause or address this element of the project. Admittedly, I find I have less and less need for this material (penetrating epoxies), but occasionally, it's just the ticket.

5 - As has been suggested and the physical properties clearly show, penetrating epoxies aren't an effective sealant, if waterproofing and moisture vapor penetration into a substrate is a desired goal. Most of these products dry full of out gassing pin holes and literally flash off their bulk, leaving a web of, non-inter linked, overlapping carbon molecules chains with limited ability to prevent moisture getting past it. Even with several coats, the best thing you can do to a penetrating epoxy is apply a full strength, 100% solids epoxy over it, which makes one wonder why employ the penetrating epoxy in the first place.

6 - Because of these types of products penetration, they make good paint or varnish primers. Personally, I'd rather use viscosity reduction techniques on regular epoxy resins, if I was going the epoxy as a primer route, but penetrating epoxies are also very good. I see no advantage to their use, except on highly flexible substrates, where they'll out perform a regular epoxy all day long. Given the price of primer in comparison, I use primer unless I have a specific reason for penetrating epoxy.

7 - Those that know me, know I don't care much for folks that are married to their ideals so fervidly that new information just can't be absorbed. I consider these types useless and tend to question all they might have an opinion about. Larry Pardey is a classic example of this insidious mentality. He still thinks epoxy is a fad. Dan Dannenberg is a skilled and able craftsmen, but also one of these stuck in his own rut types. He can't see past his own nose and this is a sin as he's got some mad boat building skills.

I've spent my whole life making adjustments to my understanding of the world. I was taught Pluto was a planet, but apparently it's only a planetoid. I'll bet both Larry and Dan just can't get their head around this and insist it's just a passing fad.

You can debate the penetrating epoxy myths all day, but the tests and the jury has long since come in. The big selling point with penetrating epoxy is it's ability to penetrate. Tests has shown it doesn't matter what the penetration level is, it's the quality of the cured coating that is the determining factor. This means that the penetration thing is nothing more then a marketing ploy. Just like using the word copper in a bottom coating product or the word epoxy in a paint product. Both words are designed to sell product, regardless of testing results.

[RodB]

I'm prepared to accept it penetrates better than my 10-20 percent home brew but I think if I thinned my epoxy to to 67.5% solvent I'll bet it penetrates equally well. But the real question is what does it do that neat epoxy wont?

It = CPES

I'll make a few points...
Obviously you can always coat wood with "neat epoxy" to achieve a barrier (West recommends 3 coats I think [ expensive and a lot of work]), but if you want to apply a sealer followed with paint and avoid checking... isn't it much much much easier to use the very very easily applied CPES... as a sealer and primer? Many proponents of CPES here have made similar comments... ie., they use CPES in very specific circumstances and it seems to work as described. A few have made negative remarks about their results when trying to use thinned epoxy. Finally, certainly there are volatile solvents in CPES but when the solvents are gone, what you have left in my observations is a epoxy looking material that has volume and appears like cured epoxy in a very thin layer. When you apply a second or third coat, the build is sure and evident and it does not seem to leave voids. When you look at areas where CPES has penetrated, the solidification of the matrix of the wood is easily recognized....the plasticized material so to speak. I have not see this same effect with thinned epoxy at all.

I am certainly open minded about this subject but the criticisms of the skeptics being answered by those who have tried the product seems to create a controversy for some reason. Also, I have not seen any anecdotal experiences anywhere concerning the use of CPES ending in failure.

Perhaps if one applied CPES to a piece of MDF or a wooden shingle one might observe some interesting results when cross cutting the samples compared to just thinned epoxy. I kinda think many folks will be impressed if they play around with CPES and experiment with thinned epoxy.

RodB

[johnw]

One part of this discussion is what result are you looking for? Do you want a sealer? Do you want a primer? Do you want a biocide. CPES has it's place, but it isn't the only sealer, and it is not a biocide.

For me, the big thing is to put on a finish that will protect the plywood from checking. I gave a piece of leftover okume ply to a friend who made a hatch with it, and he painted it, and it checked something awful. I don't know what paint he used, and I'm sure he didn't use CPES. I don't want to put all this effort into a boat and have it check. On the other hand, I knew someone who worked with thinners a lot, and she died of pancreatic cancer. Mind you, she was a printer, and worked with some known carcinogens (I'm pretty sure Bestine has nasty stuff in it, for example.) I'm building outdoors, and I probably won't get hit with enough of whatever is in the stuff for it to do much harm, but a forum like this is a good place to hash out what's safe to use in what circumstances. I'm sure this won't be the last boat I build, and I'm sure others would like to know, so I'd like to find out whether there's a real advantage to the CPES stuff, or if there's an alternative that works as well without a noxious chemical cocktail.

I'm interested in the oil-based alternatives a couple people have mentioned, but I've managed to get those mixes wrong and have an oiled surface that didn't want to dry out enough to pain over, so I'd want to know what I was doing with that kind of mix before I put it on my precious little project. I've used Smith's before with good results, I just don't like working with it. On the other hand, on a little boat, I can probably do all the work I need to with it in a matter of hours.

It's interesting that people become so passionate on this subject. I can certainly understand. If I build a stitch & glue boat, and have to wear a space suit while sanding it and sealing it, it takes a bit of the romance out of the project. That's why I started the stitch & glue thread, which I learned a lot from, and why I started this thread, which I'm learning a lot from as well.

Of course, the ultimate in aesthetics of building would be to build the way Eric does, but I'm not at that level, and want to get this boat done quickly as well. Which means I'm going to be using some nasty modern chemical stuff (instead of the nasty old fashioned chemical stuff like red lead.) Best I know something before I start.

[RodB]

John,

I'm assuming you are talking about fir ply? If I took the time to build a stitch and glue hull, I can't imagine not taking the time to glass the panels before assembly...and that includes the hatches. My 5 year old Texas flats boat is as sound as the day I finished it...

RodB

[johnw]

Nope, okume ply. Same stuff I built Black Swan with, except 4 mm instead of 6 mm. I sealed Black Swan with Smiths, and the results have been good so far. The okume my friend built his hatch with was left over from the deck for a Snipe.

[RodB]

I think it narrows down to three choices... CPES, or epoxy coat, or epoxy glass...

R

[Wayne Jeffers]

For me, the big thing is to put on a finish that will protect the plywood from checking. . . .

A low-toxicity way to keep plywood from checking is to saturate it with raw linseed oil. A tip from Ken Swan that I saw in Boatbuilder magazine many years ago. I have a 10-year-old fir ply skiff that I saturated with raw linseed oil and it has never offered to check.

Saturate with as much (unthinned) raw linseed oil as it will take. When the wood stops taking up oil, wait for 15 minutes and wipe off all surface excess. Let it dry a couple of days. Prime with oil-based primer, then apply top-coats of choice.

Note: Epoxy will not reliably bond to oiled wood -- do your gluing before you apply the oil.

Also: The topcoats need to have an effective biocide because the oil seems to promote surface mildew in a damp climate.

Wayne

[johnw]

Well, a damp climate is certainly what I've got. What kind of biocide? Does the top coat need to be bottom paint?

[Wayne Jeffers]

It's often damp enough here in the Midwest, too. To be fair, I saturated the plywood, gave it an oil-based primer, then two topcoats of Sherwin-Williams least expensive exterior latex, and it has really been only the parts that have been under a silver polytarp cover that have been a mildew problem. Exposed areas have not been a mildew problem. Mildew has always washed off easily enough, but still it's been a nuisance.

I'm guessing this has been because of the underlying linseed oil, but I could be wrong about that. My problem may just be the relatively cheap latex topcoat. I've never yet bothered to repaint it.

Wayne

[pipefitter]

One thing about CPES and marine ply is, it's not going to soak past the paper thin veneer that is on the faces of most marine panels these days. There's a waterproof, and I suspect, CPES proof glue line after that. A lot of regular epoxy soaks in initially as well. I am not certain it matters all that much with plywood, and may well be that the surface being sealed works as well as penetrated.

We know that straight epoxy soaks into end grains sufficiently enough.

[Wayne Jeffers]

In my experience, epoxy coating alone will not prevent fir ply from checking; you also need a layer of glass cloth with the epoxy. I doubt CPES would do any better, although I have never tried it.

Sealing and preventing checking are two different things.

Wayne

[wizbang 13]

Okkume here , not fir.
1088 ply, uses full thickness on the outside layers. It is one of the main things to look for when buying ply. If one has ply with paper thin outside layers, it is a big strike against it for boat building.

[purri]

Interesting but I fail to see how the method(s) deal with inherently "greasy" timbers.

[johnw]

Interesting but I fail to see how the method(s) deal with inherently "greasy" timbers.

I'm just dealing with okume plywood, but wouldn't inherently greasy timbers be sort of immune to checking?

[willin woodworks]

When I say that CPES works (Has worked) better than thinned epoxy I am refering to it's qualities as a primer and a sealer. I can only speak from my experience but I have found that the surface of solid wood that has been premed/sealed with CPES is smoother and more unfiorm that that sealed/primed with thinned epoxy. End grain penetrations is greater in ply and in solids and the "Plasticised" appearance that has been referred to appears much more stable and uniform.

[Todd Bradshaw]

If preventing checking is the goal, then I think Wiz hit the first nail on the head - the quality of the plywood is the biggest factor. Checking is caused by cycles of moisture absorption, followed by drying out. The surface layers actually expand and contract and depending on the quality, species, veneer thickness, glue type and maybe even whether peeled or sliced you can pretty much bet that all plywoods are not created equally. There seems to be a pretty substantial amount of force present when the stuff wants to crack and if you're expecting to overpower that force with a vapor permeable application of diluted resin, theoretically glueing all the fibers together so that they can't expand, contract or move, I think you're dreaming. Even a fairly substantial coating of unthinned epoxy is probably not the solution because it has little strength. Epoxy/fiberglass coating has shown to be most effective because of a couple of factors. The first is the tensile strength added to the equation by the glass, which is drastically more than that offered by any liquid coating alone and about the only thing that has much chance to overpower the expanding/contracting forces (though it still may not be completely effective). The second is that the glass acts as a thickness guide for the resin, making sure that you have the required 10 mils or whatever it is that's needed to form the most effective moisture barrier (though again, it probably won't be perfect).

It doesn't matter how deep something penetrates if it's not very strong in the first place. Sure, you can watch diluted resin get sucked up by some punky gingerbread trim from your front porch and make it hard, but that has little to do with boats or sound wood. I'm not anti-CPES and think there are some uses for it (improved paint base) but I do find some of Smith's ad hype so full of bull that it's offensive and doesn't do the product any good. And if resisting checking is the main goal, I'd probably use that money to buy better plywood or some 6 oz. glass cloth.

When Kool-Aid is offered, it's usually a good idea not to drink all of it.

[johnw]

I'm going to be carrying this boat on my back. Glassing it would add a lot of weight, so I don't think I want to go that route.

[RodB]

Todd,

You are always very analytical and logical... I would like to point out that the pro CPES people on this thread make specific claims for their personal experience while pointing out the studies from the Forest restoration site. Those studies are very interesting as they measure water weight gained in porous materials with and without treatment with CPES. You and I are on the same page about glassing the plywood for a boat, but it is interesting that John used cpes before and did not have any checking.

I have not seen any of the okoume I have used check (some in my garage for 5 years on a rack close to the door) but it has always been at least double coated with System Three epoxy or glassed if in a boat project. I'm temped to prepare a few pieces with paint only, primer and paint, CPES and paint etc and leave them out to see what happens.

You do point out that all plywoods are not equal and I'm sure this would be one of the major factors when checking takes place. I have only bought quality marine ply Okoume form World Panel in Miami... and have never had any concerns.

If you go with a "given" that the plywood that was only coated with cpes and painted and didn't check was an averagel Okoume ply... then did the CPES , minimize the amount of moisture movement so that checking did not take place? What are the chances the ply would not have checked anyway without CPES prior to paint?

I use CPES for very specific situations and find it a good tool to keep around the shop...but I'd bet it wouldn't stop fir ply from checking... and I have always been under the assumption that most decent Okoume ply wouldn't be likely to check if primed and painted with good materials. I have read and been told that fir ply has checked with epoxy coating... and that only glassing will keep fir ply from checking.

John,
I have seen first hand the protection offered by glassing ply over time... from both abrasion and moisture intrusion... I'm thinking boats can be built very light with 4 oz cloth applied to the surfaces... or even 2 oz cloth.


RodB

.

[johnw]

I'm wondering how much protection a thin layer of epoxy and milled glass would give. I wouldn't be relying on it for strength.

[Todd Bradshaw]

Rod, I have 25 year old Okoume floor boards from my old Avon sportboat. A couple spots are reinforced with Kevlar and WEST 105/205 on their back sides, but about 90% of their surfaces, including the edges are protected only by Captain's Varnish which has been maintained. No checking or any other problems. The difference? It well might be because I built them from Bruynzeel Okoume. If I still had the stack of that stuff and the stack of 20' sitka 1x12s that I once had, I'd be one happy camper!

Milled glass? Just about the same amount of protection as plain resin would. What is the milled glass really adding to the equation? Not much. By the time you got enough of it in there to do much more than just thicken the resin, or reach a high fiber-to-resin ratio, the stuff would be totally obnoxious to try to cover a boat with and at the same time, lack the directional tensile strength of continuous fiber woven cloth.

[johnw]

Rod, I have 25 year old Okoume floor boards from my old Avon sportboat. A couple spots are reinforced with Kevlar and WEST 105/205 on their back sides, but about 90% of their surfaces, including the edges are protected only by Captain's Varnish which has been maintained. No checking or any other problems. The difference? It well might be because I built them from Bruynzeel Okoume. If I still had the stack of that stuff and the stack of 20' sitka 1x12s that I once had, I'd be one happy camper!

Milled glass? Just about the same amount of protection as plain resin would. What is the milled glass really adding to the equation? Not much. By the time you got enough of it in there to do much more than just thicken the resin, or reach a high fiber-to-resin ratio, the stuff would be totally obnoxious to try to cover a boat with and at the same time, lack the directional tensile strength of continuous fiber woven cloth.

I was thinking in terms of abrasion resistance, but it would take more than a thin layer to do that, I suppose.

[Cuyahoga Chuck]

One thing about CPES and marine ply is, it's not going to soak past the paper thin veneer that is on the faces of most marine panels these days. There's a waterproof, and I suspect, CPES proof glue line after that. A lot of regular epoxy soaks in initially as well. I am not certain it matters all that much with plywood, and may well be that the surface being sealed works as well as penetrated.

We know that straight epoxy soaks into end grains sufficiently enough.

Any marine ply that is claimed to meet BS1088 standards MUST be made from approximately equal thickness verneers. That is one of the stated elements of the standard.

[willin woodworks]

Neither CPES nor any epoxy coating without glass is going to prevent checking in fir ply. Bet on it. CPES may reatrd and may minimize (MAY) the checking of fir ply but prevent? Never.

As someone else has already stated; if you're using ply with a paper thin outer veneer, you bought the wrong stuff. Marine ply should have equal thickness plys throughout.

[johnw]

Neither CPES nor any epoxy coating without glass is going to prevent checking in fir ply. Bet on it. CPES may reatrd and may minimize (MAY) the checking of fir ply but prevent? Never.

As someone else has already stated; if you're using ply with a paper thin outer veneer, you bought the wrong stuff. Marine ply should have equal thickness plys throughout.

I'm not using fir ply.

[JormaS]

Having skimmed through this thread I can't see any votes for a linear polyurethane paint. What's wrong with LPU in this application? Just wondering.

[Todd Bradshaw]

If you want abrasion resistance, mix your epoxy with carborundum grit. Your boat will leave grooves in rocks - though it may weigh just as much AS the rocks.

[Paul G.]

Having skimmed through this thread I can't see any votes for a linear polyurethane paint. What's wrong with LPU in this application? Just wondering.

LPU is a finish coating, not suitable as a primer. CPES has some pretty strong followers on this board, what I get from the discussion is that it is a good primer (and so is warmed neat epoxy and thinned epoxy as well as paint) The benefits of penetrating epoxies are debatable because it is not a substitute for a thorough repair, nor does it really matter how far an epoxy penetrates as it is the surface coating that is important in keeping moisture out. I have to agree that when you see epoxy soak into wood there is a significant feel good factor, but the evidence and testing shows that apart from being a good primer in certain circumstances the actual benefit is minimal.

Regarding the checking problem, no thinned epoxy by itself is going to solve that problem, a thinner surface veneer may actually be of benefit as the glue layer will be more effective a resisting movement. To truly stop checking, a covering with boatcloth and epoxy is probably your only solution. Personally I have never had a problem with any marine ply checking that has been coated with neat epoxy, and construction ply that has been glassed.

[RodB]

CPES has some pretty strong followers on this board, what I get from the discussion is that it is a good primer (and so is warmed neat epoxy and thinned epoxy as well as paint) The benefits of penetrating epoxies are debatable because it is not a substitute for a thorough repair, nor does it really matter how far an epoxy penetrates as it is the surface coating that is important in keeping moisture out. I have to agree that when you see epoxy soak into wood there is a significant feel good factor, but the evidence and testing shows that apart from being a good primer in certain circumstances the actual benefit is minimal.

What a bunch of baloney... thinned epoxy is not the same as CPES ( as a primer or anything else). I specifically remember a thread on this subject a few years ago where a guy took a board, cut it in half, and coated one piece with CPES and the other he did not... next he painted both boards with a couple coats of an exterior alkyd enamel.

He left these boards outside to suffer the perils of wind, sun and rain...for the next couple years and I think at the time he was writing the post, he said the CPES coated board was as sound as the day he put both boards outside and still going srong, the board with no CPES was in poor shape as the paint had deteriorated because of water ingress into the board.

This wasn't a very scientific study but it is yet another anecdotal experience like several others in this thread where individuals post their positive personal experience with CPES. Edited to add: Two years is not very long... but this example at minimum shows the paint was not all that good but the CPES added enough of a moisture barrier that the sample treated with CPES faired better.

CPES does have some very real benefits (if you want to call it a thinned epoxy or not). The point of this thread is that CPES is convenient way to achieve some added insurance against moisture ingress without having to coat the surface with regular epoxy. It also allows one to get an extremely good bond with paints and varnishes that are applied within 12-18 hours or something like that.

I also have my own experiences where CPES filled the cells of a porous wood and definitely made it stronger, more stable and "plasticized" it more or less. That aint going to happen with thinned epoxy (regular epoxy thinned with a recommended solvent.

RodB

[Todd Bradshaw]

That's not really much of a test. I have wood trim on my house that was painted with Brightside five or six years ago and is doing fine. This small box-like extension on my garage wall was built out of Home Depot fir exterior plywood in 2000. It got two coats of rolled on WEST 105/205 and a couple coats of white Brightside. It gets sun exposure for at least half the day and is obviously outside year-round. The ply finally started to check last year and I tore it out and built a new box. "A couple years" should be easily possible with just a decent paint job.

I'd also be careful about assuming that making something harder is making it stronger. It's often not the case, and assuming that CPES (which any way you want to call it is still diluted epoxy) is making something stronger when it comes to boat wood is most likely a mistake.

[RodB]

When am I going to learn to qualify everything with Todd on the job?

The example I cited above was only at two years... and he said he would continue to observe the test pieces. A solid scientific study would certainly be nice to see here. I'm thinking if the sample coated with CPES withstood the two years better than the non treated sample, it certainly says something about CPES and the paint that was used.

Todd, did you read the Forest restoration link on the effectiveness of CPES? I've seen enough to convince me that CPES is worth using for very specific situations and I don't need to have a full scale 10 year study to decide whether to use it or not. The studies shown on the Forest Restoration cite that are based on weight increase due to water penetration of CPES saturated samples are well enough executed to convince mes of CPES's effectiveness as a moisture barrier. Of course its not going to be as effective as standard epoxy at a proper mill thickness, but we are not talking about using CPES vs standard epoxy, are we?

Lets just say that some of the instances where I used CPES it did fill the majority of the cells and when the sample piece was crosscut, it was a more or less solid matrix... to me, it would make sense the sample with a more or less solid interior ... was somewhat stronger than the untreated piece. If you saw the cross cut samples, you would pretty much assume the solid matrix sample would be stronger than an untreated sample. I may be wrong to make any assumptions, but in a general sense, CPES is well worth using in very specific situations as added insurance against moisture ingress and of course stabilizing deteriorating wood. From my personal experience, I think CPES stabiizes wood in various stages of degradation and is also easily applied.

No one in this thread including me has tried to compare CPES to standard epoxy for any kind of use... except it does penetrate porous woods well and fill the voids to a high degree when standard epoxy would not penetrate much at all. The point is CPES penetrates very well into wood. My experience with thinned epoxy was negative and I will not even consider thinned epoxy in the future for any use.

RodB

[Todd Bradshaw]

but we are not talking about using CPES vs standard epoxy, are we?

Actually, if we're talking about this thread's original title and answers to the checking question posed in post #1 (which is worth re-reading) I think we would have to be mentioning epoxy, or fabric reinforced epoxy as one of the best available solutions. We would also need to address the question of whether or not good quality Okoume marine ply needs anything other than paint, varnish and reasonable maintenance (which has been mentioned). We have also heard from folks who had good luck with oils. I think you are way too hung up on the penetration thing - and what exactly is "porous wood"? If somebody asked me if I wanted to take a ride on a boat that was being kept afloat by structural wood which had been porous and was now "strong" due to deep penetration of some sort of mystery goo that's mostly thinners, I'd take a flying leap - for the nearest dock.

Standard epoxy seals about as well as anything you can possibly find due to it's high solids content and will stick tenaciously with very shallow penetration. So will tar, though it tends to be rather impractical. Penetration may be important for Smith repairing rotten decorative archetectural do-dads, but it doesn't mean much for boatbuilding or sealing boat wood.

[hokiefan]

The smell is a very toxic mix of thinners, remember the bulk of the 2/3rds solvents are common cheap thinners like xylene and toluene.

There is nothing good for you in toluene. The CPES MSDS doesn't list the concentration, but its third on the list so its the third largest component if they did the MSDS right. In the industrial world toluene requires excellent ventilation or an organic vapor cartridge respirator. Toluene is an excellent solvent, part of its toxicity is because it dissolves parts of you.

Cheers,

Bobby

[johnw]

There is nothing good for you in toluene. The CPES MSDS doesn't list the concentration, but its third on the list so its the third largest component if they did the MSDS right. In the industrial world toluene requires excellent ventilation or an organic vapor cartridge respirator. Toluene is an excellent solvent, part of its toxicity is because it dissolves parts of you.

Cheers,

Bobby

ick.

[hokiefan]

ick.

It can be done safely. In a former life we use millions of pounds a year. But where you have it in the open you have excellent ventilation. There are worse chemicals to work with, my current life has a long list of them. You just have to identify them, learn about them, and take the appropriate measures so they are on the other side of proper barrier.

Cheers,

Bobby

[johnw]

Thanks, your expertise is appreciated.

[pipefitter]

I have seen a lot of marine panels with thin, 'A' grade face veneer. In fir, meranti and occoume. Also with a claimed rating of BS 1088. BS has not meant British Standard for many years but the letters still apply for another abbreviation.

I am neither for nor against CPES. I just happen not to need it. I used regular epoxy as a primer so that my paint would hold a wet edge in this hot, humid climate longer. When you put on slick coats down here in Summer with a brush, your feet better be moving.

If you buy the solvents separately that are in CPES, and a gallon of epoxy, you can have close enough to the same thing for pennies on the dollar. I did an experiment using interlux's epoxy paint thinner 233N and regular two part epoxy. I put a paint paddle into a 1/4 full pint jar. It wicked to about the 3/4 height on the jar.

233N contains:

Naphthalene (This is the main ingredient in mothballs IIRC. I can see where that would have some anti-rot properties in itself.)

Cyclohexanone

Methyl n−amyl ketone

Ethylene glycol monobutyl ether acetate (Could this be of the same ethylene glycol purported to prevent rot in wood?)

Acetic acid, C6−8−branched alkylesters

From Wiki.

Trace amounts of naphthalene are produced by magnolias and specific types of deer, as well as the Formosan subterranean termite, possibly produced by the termite as a repellant against "ants, poisonous fungi and nematode worms.

[Paul G.]

Stopping ply check is probably a local environment and species choice issue. Ive used meranti, gaboon, hoop, fijian maple & kauri, pine, mixed grade (whatever that is) white meranti etc and Ive had no checking at all, but all ply exposed to the sun has been well glassed and painted white.

[Wayne Jeffers]

If you want to avoid checking, it seems your choices are:

1) Choose a species of plywood that is not prone to checking, or

2) Cover the plywood with fiberglass cloth set in epoxy, or

3) Saturate it with raw linseed oil and take your chances with mildew, or

4) Fill the checks with something like Interlux trowel cement (if you can find an old can somewhere) and repaint.

I actually dug out the old issue of Boatbuilder (September/October 2001, p. 26) and found the sidebar about linseed oil and plywood checking. Ken Swan suggested using an oil-based topcoat over the oil-based primer.

My mistake with my skiff may have been trying a hybrid of Ken Swan’s raw linseed oil plus Dave Carnell’s latex house paint over the oil-based primer. I may also have been asking the impossible by keeping it under a polytarp cover where it could not get proper ventilation.

Of course, if we still had lead in paint, mildew would never be a problem, although many of our children would be brain-damaged or dead. I’m not sure what chemicals are used in paints these days to inhibit mildew and what the realistic life-expectancy of those chemicals may be. No doubt some paints are better than others in this regard. Come to think of it, mildew has only been a problem with my 10-year-old skiff in recent years.

Wayne

[Lewisboater]

233N contains:...

Acetic acid, C6−8−branched alkylesters

Hmmm...I use Vinegar ("Vinegar is a liquid substance consisting mainly of acetic acid (CH₃CO₂H) and water" Wiki) which is 5% Acetic acid as a kill cure...it stops the cure of epoxy. Don't know if I would want to thin my epoxy with something that will inhibit or prevent it from curing, regardless of whether thinning is something that is useful or not.