How much epoxy is in CPES vs West System

[Steamboat]

Having the urge to kick the hornets nest I decided to do a little experiment comparing CPES to West System epoxy and post it here to stir the pot. My only reason for purchasing CPES was to try and preserve a rotting log carving that my wife loves. Other than to say that the CPES has stabilized the rotting wood of the carving, I will make no other claims about the product performance in preserving wood.I put the same volume of CPES (2) and West epoxy (1) into two ‘identical’ bottles. The epoxy formed a solid cylinder of the original volume. The CPES formed a soft gel that reeked of toluene and xylene. After two weeks out in a warm shed away from the house the CPES was still a soft gel and still reeked of toluene. The evaporation of the solvents from the CPES gel was so slow that I dislodged the gel from the bottle broke it into fragments and spread the CPES gel on a pie plate. Some weeks later the toluene smell was gone and I had a pie plate of hard CPES fragments. These fragments were poured back into the original jar (3) for a rough volume comparison to the West epoxy. The bottom line is there is that volume of CPES is not about 1/3 of original CPES gel and 1/3 of the West epoxy. This implies that the original volume of CPES was 2/3 solvent.which, by my nose, is mostly toluene.The bottom line is you get less epoxy per unit volume in CPES than your standard epoxy resin.

[Ian McColgin]

Yep. And if you're feeling real scientistic you can put a couple of drops of pain in a pint of thinner and leave it out back for a while . . .

Not sure what you've learned that you'd not understand just reading the directions of these two very fine products.

[Steamboat]

Yep. And if you're feeling real scientistic you can put a couple of drops of pain in a pint of thinner and leave it out back for a while . . . Not sure what you've learned that you'd not understand just reading the directions of these two very fine products.

This was motivated by all the arguments about what you are paying for when you buy CPES and how much is epoxy and how much is solvent. I have no problem with the product when use for its intended purpose of repairing rotted wood.

[MN Dave]

Weighing the residue would tell you more than the volume. The gel is porous, and random shaped debris does not pack well.

I like the typo Ian. I don't know how to put pain in thinner, but it would be nice to get it out of my knee.

[Garret]

...I don't know how to put pain in thinner, but it would be nice to get it out of my knee.

For many, becoming thinner helps the knee pain considerably...

@ the OP: I have had great luck with both products (when used for what they are intended) & have found that thinned West is not the same as CPES when it comes to penetration.

[Todd Bradshaw]

Penetration with regard to epoxy products is very highly overrated (and in most cases, not particularly necessary). There are even serious questions with epoxy/solvent mixtures regarding just which, or what percentages of these ingredients are actually doing the penetrating. There is really no guarantee that the solvent is pulling the epoxy in with it as it "penetrates", and solvent-soaked wood doesn't have much benefit unless you want to start a fire with it. Most of Smith's hype is aimed at folks who don't know any better. My wife has a Ph.D in chemistry and holds five molecular biology patents. She gets a good chuckle out of the CPES "scientific" advertising hype.

[MN Dave]

CPES and chromatography?

[Steamboat]

CPES and chromatography?

That's not paper chromatography or thin layer chromatography, its wood chromatography. Which is just about what the claims for CPES are. . .

[Steamboat]

Penetration with regard to epoxy products is very highly overrated (and in most cases, not particularly necessary). There are even serious questions with epoxy/solvent mixtures regarding just which, or what percentages of these ingredients are actually doing the penetrating. There is really no guarantee that the solvent is pulling the epoxy in with it as it "penetrates", and solvent-soaked wood doesn't have much benefit unless you want to start a fire with it. Most of Smith's hype is aimed at folks who don't know any better. My wife has a Ph.D in chemistry and holds five molecular biology patents. She gets a good chuckle out of the CPES "scientific" advertising hype.

The guys doing nanoparticle research use acetone (10% by wt) to improve the dispersion of nano fillers into epoxy resin. They suggest that higher concentrations of acetone interferes with the rate of polymerization and the durability of the final product. They also suggest that less volatile solvents should not be used since they interfere with the completeness of polymerization. The nanoparticle experiments were done with dicyandiamide as the "hardener". Who knows what is being used in CPES, I have not been able to fine on Smith web pare.The bottom line is you are paying a lot for toluene and xylene, two solvents that should be used with caution.

[MN Dave]

, I have not been able to fine on Smith web pare.The bottom line is you are paying a lot for toluene and xylene, two solvents that should be used with caution.

The part about the solvent is true. It isin't on the Smith page, but not exactly hard to find.
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[JimConlin]

Makers of such products are required to fess up about their ingredients and the fraction of Volatile Organic Compounds VOCs), meaning solvents.
Especially with proprietary snake oils like CPES, makers try to be coy. The CPES published data is a model of obfuscation, listing about 20 components, each comprising 0-50% of the product. IIRC, Someone did some lab analysis and concluded that CPES is about 2/3 solvents. For the TotalBoat product, it looks like it’s lower.

[Nicholas Carey]

I like some of the text on Smith & Co's CPES page:

---

Smith's Clear Penetrating Epoxy Sealer is the only product made largely from the natural resins of wood itself.
. . .
Wood naturally contains water, typically 8% to 15%, even 25% or more in humid environments such as around boats or in chronically humid climates. The solvent system that carries the natural wood resins of Smith's Clear Penetrating Epoxy Sealer into the wood has to be capable of dissolving that water [emphasis mine], so that the penetration show [sic] in the prior examples can happen.

---

Take a look at these more recent MSDS' for CPES. It's a laundry list of nasty solvents:

• MSDS, CPES, part A
• MSDS, CPES, Part B

On top of toluene and xylene, it's a veritable cornucopia of other solvents, including Methyl-[something]-Ketones.

[nedL]

I have never tried or used CPES. I do occasionally use Minwax “Wood hardener” which in some cases may be a different path to a similar end. It is a water thin water clear single part liquid that I take to be somewhat like a thinned out urethane varnish. It realy does not restore much strength, but does seem to do an excellent job of preventing wood (esp endgrain) from absorbing water, which prevents further rot.

[Ian McColgin]

I remember the first time I used CPES coming up to the statement running something like, "WARNING, this product cannot be made safe."

As we have noted often, that weasel pssss can cause cancer in rocks.

And yes, you are paying for solvents.

On my various old boats, I've installed a few hundred dutchmen of various sizes in spars, decks, hull planks, and frames. I chop away past detectable rot but there's always spores running out ahead and I have found I have a better outcome if I CPES the faying surfaces, especially soaking the endgrain. I use WEST for my gluing epoxy and always put unthinned on the faying surfaces before putting in whatever thickened I feel I need - the better the joint, especially if subject to bending, then thinner I go - and have had no compatability problems and have found no need to wait between the CPES and the real glue-up.

I think Rot Doctor overstates a bit but when I got Marmalade if found that the old plywood decks with teak veneer were a bit spongey. I reefed out that think layer of black faux calk lines and in the course of a hot dry July I occasionally sloshed the deck down with acetone. Finally, I invested in a couple gallons of CPES and soaked that in. It actually worked and made ripping off the cabin and deck unnecessary. It's not a solution for all problems and it's expensive. It is very rarely a good idea to leave bad wood in place for weasel pssssing, but there are times when it does make sense.

[paul oman]

the west epoxy is 100% epoxy (solvent free)
the other product is 31% epoxy and the rest is a blend of solvents (mostly naphtha) - sort of epoxy thinned solvent

[jackster]

the west epoxy is 100% epoxy (solvent free)
the other product is 31% epoxy and the rest is a blend of solvents (mostly naphtha) - sort of epoxy thinned solvent

Shouldn't that be epoxy thickened​ solvent?

[Ian McColgin]

For a glue, having a product that's as much epoxy, as little solvent, as possible is wonderful. It's what allowed me to get started with WEST before there was much in the way of additives. Epoxy has wonderful gap filling qualities thickened in various ways - some very soft for easy fairing, some hard enough to be cast structures of their own, like structural fillets, and some where we don't think of it as thickened because we use unthickened when glassing but think about it.

It's so good it gets over-used. Fat uneven glue lines are not just sloppy work. Thickened epoxy allows for sloppy work and hard spots. These on a scarf mean the wood can't flex as it should. The transfer of stresses though the timber are changed and localized. Epoxy is so strong that this might not lead to failure. Might not.

And when a sloppy joint or lamination done up with hard thick epoxy does, the epoxy pulls a bit of wood away. This leads people to think that the epoxy didn't fail, the wood failed. Not so at all. The joint, an epoxy/wood structure, failed.

Unthickened WEST is just right for most glue-ups with clean mating faying surfaces. It's a glue.

CPES is not a glue. It's job is for the solvents to carry micro amounts of epoxy into the wood. It is "just thinned" epoxy. Personally I have used a couple of (my experience) terrible propriataries like Git Rot and I have thinned WEST with recommended thinners. I did not get anything like the results I get so easily and repeatedly with CPES, but then I am not the smart chemist that Mr. Smith is.

Or that Paul is, for that matter.

Or a couple of OSU grad students I knew in the '70s who called themselves "epoxy engineers" and mixed different formulations depending on whether they were gluing a bridge back together or a leaky dam face or what. Today composits dominate well beyond marine and aeor-space industries.

People who understand the chemistry and work with non-standard applications can buy generic and modify to suit. For people like myself, getting very familiar with a finite number of propriatary products is the way to get reliably replicable results.

[David G]

Weighing the residue would tell you more than the volume. The gel is porous, and random shaped debris does not pack well.

I like the typo Ian. I don't know how to put pain in thinner, but it would be nice to get it out of my knee.

'


Some find that drinking the thinner will help with the pain. I prefer single-malt thinner.

[tonino]

Two totally different products with two totally different purposes, 2 totally different application techniques.

[wizbang 13]

I dunno how “lite beer” gets away with that name, five cases of it is just as heavy as regular beer.

[Boatbum]

Having the urge to kick the hornets nest I decided to do a little experiment comparing CPES to West System epoxy and post it here to stir the pot. My only reason for purchasing CPES was to try and preserve a rotting log carving that my wife loves. Other than to say that the CPES has stabilized the rotting wood of the carving, I will make no other claims about the product performance in preserving wood.I put the same volume of CPES (2) and West epoxy (1) into two ‘identical’ bottles. The epoxy formed a solid cylinder of the original volume. The CPES formed a soft gel that reeked of toluene and xylene. After two weeks out in a warm shed away from the house the CPES was still a soft gel and still reeked of toluene. The evaporation of the solvents from the CPES gel was so slow that I dislodged the gel from the bottle broke it into fragments and spread the CPES gel on a pie plate. Some weeks later the toluene smell was gone and I had a pie plate of hard CPES fragments. These fragments were poured back into the original jar (3) for a rough volume comparison to the West epoxy. The bottom line is there is that volume of CPES is not about 1/3 of original CPES gel and 1/3 of the West epoxy. This implies that the original volume of CPES was 2/3 solvent.which, by my nose, is mostly toluene.The bottom line is you get less epoxy per unit volume in CPES than your standard epoxy resin.

I would imagine so. CPES is supposed to penetrate and what better to aid in that then large amounts of solvent which slow the hardening, make it more liquid, and to soak into things. You will get a similar effect by diluting standard epoxy with acetone (as much as 50/50). Of course you lose considerable strength, but if your goal is to soak the wood making it more rigid and less water absorbent, the strength doesn't matter that much. Most here will recommend against diluting epoxy and if your goal is to bond and/or strengthen they are right. But I's also seen successive coats of diluted epoxy get soaked up by dried our near rotting wood. It dries so slow that you can keep adding coats for a couple hours and each coat soaks in nicely. In the end it is harder and water resistant if not waterproof. I realize I am proposing heresy, but that seems to me what CPES is anyway. It has always worked well for me, but keep it away from frames and planks. Always something non-structural.