View Full Version : CPES Question

04-06-2007, 06:56 PM
As some of you know I'm restoring a very old Beetle Cat - my first restoration project. I had never heard of CPES before joining this forum and plan to use it on questionable wood. It seems like you folks are using it on just about everything and quite often. My question is under what circumstances should this product be used and what level of wood deterioration makes CPES ineffective?

04-06-2007, 08:03 PM
Before CPES acquired magical powers and legendary status on the WoodenBoat Forum it stood for Clear Penetrating Epoxy Sealer and my wild guess is that is what it is - a sealer, albeit a very good one. Personally I would use it to seal good wood, and not waste it on bad wood, and not expect CPES to behave as anything more than a good sealer. Others may point out that I've never actually used the stuff.

04-06-2007, 08:19 PM
I'm one of the folks that use CPES for some jobs, but certainly don't credit it for everything claimed in some of the ads, and don't use it for all priming/sealing work.

From what **some**of the experienced folks here say, it makes a good undercoating / sealer for varnish and paint -- and I've found that to be true.

Some paint and varnish failures are due to the paint/varnish detaching from the wood -- and if you can get a bit of penetration from the CPES, supposedly you can reduce that detachment failure. Others use thinned varnish or thinned epoxy for this seal / primer coating.

I used the Smith & Co CPES mixes with their epoxy and epoxy fairing compounds, but of course there are other makers. A primary use for me was on some partially-rotted fir bottom planks. As recommended by Steve Smith, I cleaned out the rot with a wire brush by hand, then got out the respirator with fresh organic filters.

I used MEK to clean the rotted wood - nasty stuff, best used outdoors on a windy day. Then I soaked/coated the wood with CPES -- ditto use with a respirator outdoors as it is nastier than MEK!

After several coats of CPES, I filled any hollows with the epoxy fairing compound, painted with red lead primer from Kirbys, then with bottom paint. It seems to be holding up well, but the boat has only been campaigned for a full season.

If you decide to use CPES, you should read up on it and make up your own mind. Here is the Smiths info pages -



Andreas Jordahl Rhude
04-07-2007, 07:09 AM
CPES is a sealer. It does not get rid of rot or magically cure it. Replace the rotten wood.


04-07-2007, 10:38 AM
There is a product named "Git Rot." Supposed to control rot in a boat. Used to be that use of the product would mark one as a duffer.

Many years later Smith makes Restor-It. (sic) It is more commonly known as CPES...clear penetrating epoxy sealer. If one reads the label it was produced for stabilizing rot degradation in architectural elements.

There are many true believers in the miraculous properties of this product. Most are found within the four corners of the screen you are looking at. It's a strange local phenomenon.

Others will understand that the only way to rid a member of rot is to replace it.

Bob Cleek
04-07-2007, 12:45 PM
I'll take the blame for being the first to tout CPES in here. I've used it for years and years with great results. It is a staple for me and many others. All of the above posts are entirely correct. I know Steve Smith, the manufacturer, who is a Chemist with experience in wooden boats, and I've talked with him about CPES a fair bit, so now, for a bit of history:

CPES is a SEALER! It was originally formulated "to restore decayed architectural elements." What this means is that by cleaning out the really bad rotted wood, soaking the piece in CPES and filling and fairing with epoxy before painting "architectural elements" (i.e. non-load bearing carved trim pieces and such) could be preserved and given a bit of a new lease on life. This is pretty neat if you are restoring an old Victorian or if the top side of a glue lam beam that extends out into the weather is rotted, but the rest is sound. It is useless if you want to repair a rotten structural member! In a marine application, rotten wood should be REPLACED!

CPES is also an amazingly effective sealer, particularly in the marine environment. (IMO it would be overkill if, say, painting your house.) This is not because it "encapsulates" the wood or totally prevents moisture from entering the wood, which it DOES NOT do (although it will slow the cycling somewhat, to no effect one way or the other.) It is a good sealer because it penetrates the wood well (owing to the specialized solvents it contains) and because the epoxy will molecularly bond to paint or varnish if the coating is applied to the sealed part within a day or two while the epoxy is curing. CPES sealer will in large measure prevent the wood beneath paint or varnish from becoming saturated and causing the paint or varnish to separate and lift from the wood, a common reason for paint and varnish failure, particularly along joinerwork seams which open and close with movement on boats. (Like anything else, CPES isn't forever... it too will eventually degrade, and it has NO UV resistance, depending for that on the coating applied over it. It does, if used properly beneath a correctly applied varnish coat, extend the life of a decently maintained varnish job maybe by a factor of four in my nearly thirty years of experience using the stuff regularly.)

CPES is not just "thinned" epoxy adhesive, nor is it just thinned "Git Rot" (which is IMHO truely crap). It is a specific formulation designed and tested for the purposes above.

Now, Smith's is an industrial coatings company which produces their products in huge batches for industrial and military customers. They aren't in the retail product business, although they do sell small batches to boat builders out of the "back door" of their factory in Richmond, CA. While I don't know the exact nature of his relationshiip with Smith's, some middleman purchases large containers of CPES and apparently repackages it in cans bearing the label "Restors-it." His advertising, which I've seen in WasteMarine, claims that "his" product will "restore" rotten wood to a stronger than new condition. His claims, which are way over the top, may be arguably accurate, depending on what you mean by "better than new." THAT'S a subjective assessment. Bottom line, CPES won't "restore" structural members in a boat. It is just a really great sealer as far as it goes in marine applications. Sometimes, you can get by using it to stabilize a bit of soft wood on the surface of a non-load bearing piece, but that is really a dicey way to go. Use it for sealing under paint and you won't be disappointed. Consider rot like cancer. You MAY sometimes put it in "remission" with "chemotherapy," but the only way to really stop it "metastisizing" is to cut it all out!

Wild Wassa
04-07-2007, 03:01 PM
I use it. I like it. I think that it describes rot well. Rot that I wouldn't even have known existed (by staining the rot). I think that it works well and does what the manufacturer claims that it does. I only use it for what the manufacturer recommends is CPES's use.

I would not seal new timber with CPES. CPES is 75% solvent(s). CPES is a timber preservative that attacks existing rot. There are plenty of other timber sealers that are a fraction of the cost of CPES ... like normal thinned epoxy, for example.

I think that I can attribute to having saved 'my boat' because of having used it. I'm sure there are other similar products that would have done the same. Having found CPES several years ago, thanks to being on WBF, I have no need to switch products.

With CPES, remove the rot as much as possible, then totally saturate the area with CPES. I often apply 7-8 coats of CPES and I only stop when the timber no longer takes up CPES which could be as few as 2-3 coats. The CPES then forms a matrix around the existing rot (it goes hard) encasing the rot. The rot is then deprived of nutrients ... stopping the rot.

I also paint the CPES on until I have a uniform gloss, which on not too degraded old timber, only tends to be about 2-3 coats. CPES is a very expensive product but is well worth the bucks ... CPES goes hand in glove with 'Fill-It', also manufactured by Smith and Co. Fill-It does not slump or run ... unlike some fillers.

Here are examples of how I have used CPES.


Wooding and then a wire brushing of the Laser II CB (below)


The first coat of CPES (below)


Now after a few coats of normal epoxy (the rudder has been physically keyed with #400), the foils are ready for filling and fairing.


My boat, was in a bad way. Wooded.


Sabilized with CPES and Fill-It, prior to scarfing in patches ... 31 patches in the hull in fact.


Then painted ... and she still remains in top condition, several years after taking these photos.

Would you trust a boat like this ... http://www.woodenboatvb.com/vbulletin/upload/showthread.php?t=61172 ... to anything but CPES?


04-07-2007, 03:53 PM
I made use of CPES some years ago, with many thanks to Mr.
(Bob, I sure hope they send you a check from time to time)

I have and iron fastened 1931 ketch. It was a bucket of rust when I bought it, and regular primers and sealers couldn't stop it from looking like a bucket of rust by the end of each season. I wooded the hull and used CPES as a sealer above the waterline. It's been over eight years and I'm lucky to see maybe a tiny spot or two each year. That's asking a lot of a sealer. Beyond that the advice here is dead on.

04-07-2007, 09:04 PM
Hi. I have read many of the threads on CPES and have an interest in using the product. A question probably more for our Australian members.

Most commercial shipwrights I have used don't use the product - they all seem to use Everdure by International instead. Is this a comparable product? Is the CPES by SENSEAL available here in
Australia the same as the product made by Smiths in the USA?

Thank you

Peter Malcolm Jardine
04-08-2007, 10:26 PM
Well, this place has really had the greatest number of threads on CPES and Kirbys Paint...

I started using epoxy sealers well before CPES, but only as a localized method of isolating and slowing down small pockets of rot in superstructures... Now I use it as a standard method of sealing wood before paint and varnish, especially in areas that get a lot of wear and sunlight. I still use it for small pockets of rot, and I will define that as areas less than 2 or 3 square inches. Otherwise, I take out the piece of wood... and I don't prefer to patch, I usually replace the member...

AND I still use linseed and turps for some things, and thinned varnish and so on.... really what I am seeking to do is SLOW the deterioration of the finish. There is no miracle cure or finish... but the greatest expense on a wooden boat is time... I will try anything that makes sense to increase the life of finishes, or slow a small patch of rot etc...

Anyway, a search here would provide endless answers and debate on CPES for anyone.

As for Kirby paints, I can't get them, so ..:D

Wild Wassa
04-09-2007, 03:53 PM
michaelpetrozzi, CPES has only been available here in Oz for about 4 years or so. It was first distributed by Timbertech Trading in Sydney and they (sadly) passed the distribution on to Senseal in Melbourne. When I've called Senseal and ordered things, the standard question is, "What do you want it for and how did you hear about us" ... then I say, "I want it for boat stuff and Timbertech Trading used to send it overnight, why do I have to wait at least a week to get this stuff from you and why don't you ask questions about am I happy with the slow delivery?" Michael order it well before you need it. Senseal use Universal Couriers and I'm convinced that an order goes around the universe twice before it arrives here.

I would attribute the using of other similar products to CPES by Aussie boatbuilders, to CPES's somewhat recent arrival in Oz and unless Senseal lifts their game, CPES will not be used by many in the boat industry here.

'Multi Primer' is CPES. Calling it 'CPES' tends to be how most know it. Yes, it is exactly the same product.


04-14-2007, 12:14 AM
Thanks for the reply Warren.

Interesting obervations on delivery - sounds like they have some problems. I'll bear that in mind.


04-14-2007, 03:11 AM
I have just finished coating my boat with Resoltec Re.1010. It is aimed at the same market as cpes, but is water-solvent based and very low toxic risk. First coat: equal parts of resin, hardener and water. Second coat:reduce the water by 1/2.Third coat neat resin mix. It has a slightly milky look which helps to see which bit you have done, this disapears after an hour or so. Total cure about a week, no sanding between coats if done within this time. 3 coats leaves a varnish like finish, but needs U-V protection. Two coats recomended as a primer for paint or pre-glue for ply. It goes on like a water based varnish i.e. very easily.
I canīt vouch for itīs durability, obviously, but so far very impressive.
Also compatable with any other epoxy system (it says on the tub) and priced around the same as normal epoxy.
The company is expanding, but I donīt know if they plan to sell in the U.S. Being low toxic,it could be mailed.
Very responsive to quierys on their products. Have a look www.resoltec.com (http://www.resoltec.com) and click on the union flag.
Hope this helps,
Oh. in UK it is sold by Connexion Technology Ltd.

04-14-2007, 11:18 AM
For those who have a hard time getting CPES,you can do pretty much the same thing with epoxy paint solvent that is used for brushable 2 part epoxy paints. It buys the same amount of time for soak in. In any of the sealer/restore products, it is the epoxy residue that is left once the solvents are gone.This way,you can control the viscosity with one kit of epoxy for alot less $ and still have standard epoxy that can be used for everything else. I use interlux solvent 2333N which is for brushing 2 part urethanes and epoxies. The solvent contains ethylene glycol which "may" slow rot/fungus if you are hoping for a snake oil magic in other restorative epoxies solvent mix.If it's the stench of the stuff that one feels makes the difference,this solvent stinks plenty and you would have to use the same fresh air considerations as CPES.

Rotten wood is thirsty wood and will absorb standard,thin layup resin further than you might think. It will take a few coats to get it to stay wet.

04-18-2007, 12:35 AM
It appears that if CPES is tested in a methodical way it underperforms quality epoxy systems by a very great deal.

This does not mean it is useless though - but it just might mean for some applications that there are other ways to go.

See http://members.ozemail.com.au/~storerm/Faq/Saltpreservative2.html

04-18-2007, 08:55 AM

Michael, with all respect I don't think your comparison at the above link really deals with what CPES is designed to do, or how it is commonly used. It is not a substitute for epoxy or a cheaper epoxy -- just a great sealer/primer for use **under** epoxy, varnish or paint.

CPES isn't a replacement for epoxy any more than a good primer is a replacement for the paint that is supposed to be used over it. The ability of CPES to transfer small amounts of moisture is a **good thing** when used under varnish which can also transfer small amounts of moisture.

Folks building boats from ply obviously have a strong interest in keeping water out of the wood and avoiding rot -- and that requires the best waterproof seal possible (whether epoxy, paint, or whatever).

But those of us with boats build of solid wood and very little epoxy have a different focus -- the wood will take up/swell/shrink, and needs to be able to keep the coatings like paint or varnish still attached. According to a number of folks here who have a lot of experience, CPES provides a superior form of that bonding/priming/sealing.

Nope, it doesn't magically eliminate rot, cure cancer or turn punky wood into steel -- despite some of the snake-oil claims of some marketing material. But as a sealer/primer it seems to be really good for some applications on some boats.

Wild Wassa
04-18-2007, 09:23 AM
Thorne, exactly.

Some further thoughts on CPES.

Those evaluating CPES as being an inferior epoxy are evaluating the CPES for qualities and properties that CPES does not have or for uses CPES is not recommended for. CPES has only one real purpose in life and it does it extremely well. CPES forms a matrix around the last of the existing rot that was not able to be removed, encasing the rot, depriving the rot of nutrients ... stopping the rot.

Attributing qualities to CPES that not even Smith and Co attribute to CPES ... is just that.

As a painter I do not use multiprimers. There are better primers for all paint base types than CPES ... I use specific primers for the different paint bases.

CPES does not replace normal epoxy when normal epoxy is called for ... using CPES is only one stage in the total process ... if needed. CPES should not ever be compaired to normal epoxy because it is a totally different product.

Thinning epoxy with products like a denatured alcohol (for example denatured ethanol) only works when the thinner is a reactive agent. Otherwise the structure of the epoxy is weakerned.

TPRDA was my standard thinning, wood preserving and reactive agent for use with Bote-Cote for several years before I started using CPES. TPRDA still remains my standard for the stage that TPRDA is designed for and is as important in my kit of tricks as CPES is. TPRDA does not replace CPES and nor does CPES replace TPRDA. These two products can not be compaired under any circumstances. They are totally different products with totallty different purposes ... and both are excellent for 'their main purpose in life'. 'Their main purpose in life' is to make my life as a painter easy. Which they both do very well.


04-19-2007, 01:00 AM
Howdy all,

Well argued Wild Wassa - and I agree about a quality epoxy system not being used for traditional boatbuilding.

But if the data shows that the CPES treated wood is porous to water - and supposedly air as well - and the nutrients are already available within the wood ...

That's the problem - there is no real indication as to why it should work if it doesn't cut off one of the three.

Maybe it simply works by hardening up a degraded surface? Which might be merit enough in some circumstances.

Best Wishes


04-19-2007, 07:54 AM
As I've mentioned elsewhere, the semi-current edition of _Classic Boat_ from the UK has the results so far of their 3.5 year test of various finishes on two flavors of hardwood == very interesting!

Cetol is doing the best, with Le Tonk the best of the oils, and some good marine varnishes rating the same.

One of the interesting aspects of Cetol is that is it semi-permeable to water vapor, as are some varnishes (as I understand it).

Again, what may be good for protecting or totally sealing ply may not be as good for solid wood = and I think that CPES falls into that category.

Michael - Have you tried testing the difference between ply coated with epoxy over with a fresh coat of CPES, and epoxy-coated ply without the CPES primer/sealer coat?

That's where you might find the value in this and similar products, as several of the very experienced folks on this list seem to feel that the bond between the epoxy and wood == usually the failure point in most testing == is much improved when epoxy is laid over uncured CPES.