: Pete, how does it hold up under the sun? I got an e-mail from a fellow
: asking about the use of it for pre-sealing an s&g kayak, would that be
: pricey or worthwhile, seems to me that thin epoxie like MAS and Raka
: obviate the need for it but he was thinking of DEEP waterproofing.

Good questions. Before answering, let me ramble for a while. Full disclosure: I have no financial interest in CPES. I buy it from the same source and at the same price as anybody else. Never used it until last summer. Then I got a call about waterproofing an old log house. (The call came through Nick - thanks Nick, I owe you one! ) Now this place was built in 1903, and has seen 98 Seattle winters. You can imagine how punky, moldy and insect-infested these logs were, particularly on the south side. Several had been replaced 6 years ago because they just rotted away, but they were in danger of doing the same thing due to the same conditions. When logs dry out, they develop radial checks and cracks, and any that face upward become sources for water to penetrate into the heart of the log. Then it's time for the molds and insects to chow down.

As a pretreatment for a comprehensive waterproofing regimen, I wanted to saturate the cracks with epoxy. If the moisture content of the wood stays below 20%, the molds stay dormant. And the insects haven't developed a taste for plastic. I tried several penetrating epoxies on mockups, including System 3 Clear Coat and CPES. CPES provided by far the best penetration, and I then used several gallons of it. There were places where CPES ran out the end grain of a log 10 feet away from where I was injecting it! After an overnight gullywasher, and before the rest of the waterproofing was done, I checked the substrate with a moisture meter, and found that all of the treated wood was under 7%, while untreated wood in adjacent areas was all over 18%. That right there tells me everything I need to know about the product.

Now, about boats. There are no UV blockers in the product, so any epoxy on the surface suffers UV degradation over time. But the product penetrates full depth, and the wood itself protects all of the penetrated epoxy from UV exposure. There is almost no film built, a small fraction of one mil. (One mil is .001") Deep waterproofing in wood just doesn't get any better than CPES.

There is another advantage to this product as well. All epoxies are made from phenol and acetone. Phenol can be derived either from coal tar or wood tar. Most (and cheapest) phenol comes from coal tar, and the resultant epoxy tends to be brittle. Those made from wood tar tend to be more flexible. CPES is in the latter group, according to the manufacturer, and that is a good thing for a waterproofing material. The strength of the wood is not compromised by introducing a brittle adhesive throughout the wood fiber matrix. So the boat or paddle can bend and flex without the high point loads and catastrophic failure that has been alluded to in previous posts.

For paddle applications, there is another benefit. I know from rowing in college that a rough natural wood grip causes less blisters than one with any kind of finish on it. With CPES the protection is IN the wood, not ON it. A light sanding gives a velvet natural texture that is kind both to the eye and the hands. And it's permanent.

There is a drawback, of course. A couple, really. At $32.02 per 2-pint kit, $44.95 for 2 quarts, or $144.76 for 2 gallons the stuff is pricey. And there are 18 volatile organic solvents in it, about 50% of total volume, so handling precautions, good ventilation and personal protective equipment are in order. The label says "This product is inherently unsafe. It cannot be made safe." With that said, given the small volumes and short durations inherent in boatbuilding, risks are minimal when good handling practices are used.

For my money, penetrating epoxy doesn't get any better than CPES.