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View Full Version : CPES and Captain's Varnish compatibility?



tapsnap
06-15-2010, 02:16 PM
According to the instructions that come with CPES, one should apply several coats of CPES onto new bare wood. allowing for drying and lightly sanding in between. Then a final coat should be applied as an adhesion coat for the varnish. This coat should not be fully dry before applying the varnish.
According to the instructions for Captain's varnish, when applying varnish over epoxy, one should thoroughly scrub the epoxy surface with ammonia/water solution, then sand with 120 grit and solvent clean before varnishing.

I fear that if I follow both these instructions that I am liable to end up with a disaster. Firstly, are these two products compatible? and secondly, do you have any advice regarding the application of varnish over CPES. Has anyone had experience using these two products together?

Mikeal67
06-15-2010, 02:29 PM
I used CPES with Captains Varnish and had excellent results . Follow the directions on the can of CPES.
mike

tapsnap
06-15-2010, 02:35 PM
So, no scrubbing with ammonia/water solution and sanding?

Mikeal67
06-15-2010, 03:26 PM
No scrubbing . I followed the directions on the CPES can. I put on the first coat of varnish while the CPES was still wet . Then continued to put on more coats of Varnish during the next few days .

Ian McColgin
06-15-2010, 03:28 PM
I am not at all clear on the chemistry of the amine blush, but my impression is that it happens in relation to oxygen. This makes sense, since epoxy would not work as a glue if the blush happened between glued plys.

Most cured epoxy surfaces have that blush (there are blushless epoxy coatings) and it must be removed, which is usually accomplished incidental the the light fine sanding you need to do for adhesion of the next layer of epoxy, paint, or varnish anyway. Thin coats of epoxy cured and sanded between seem to work better than "hot coating" epoxy on epoxy, but this is different from chemical bonding a coat of paint or varnish to epoxy.

IF YOU HIT IT RIGHT - epoxy cured enough that you can paint over without making a mess, but not so cured that the blush has started or that the bonding power of epoxy has stopped - then the chemical bond is really really wonderful.

I personally find it hard to hit it right, especially in large jobs, and the delay of a day to cure and then regular surface prep gives a reliably excellent bond. So, take your pick. Both ways can be screwed up but I personally am more likely to make a mess of the chemical bond approach.

Unless you're a pro with the ability to amass huge and well understood experience, it's best to find a small group of products and techniques that work for you. That's why I keep touting the same three basic products - CPES for sealant and preservative, WEST for bonding, and Gluvit for wierd mash jobs. They are not absolutely the best in all of the situations I use them for, but they are the best I know how to use. Others have had equally good or even better fortune with other propriataries.

Of all the products I've used, CPES is the only one I've actually had good fortune with hot-coating. If the job is small, the CPES deep saturation coupled with its slow cure rate really give a good bond. If you CPES in the morning and paint or varnish first coat in the afternoon (and it's not too hot or sunny) you can put that first coat on unthinned and it'll stick finastkind.

G'luck

Thorne
06-15-2010, 04:05 PM
As above. CPES is ****not**** epoxy or "just thinned epoxy", so most of the rules don't apply -- particularly those for amine blush!

Pay attention to the CPES cure time as it varies by formula and maker. Smith & Co has a Warm Weather Formula that works best at this time of year.

Steve Lansdowne
06-15-2010, 05:00 PM
CPES directions also say it works well as a primer. Don't think of it as Epoxy, as it is not.

sdowney717
06-15-2010, 05:46 PM
http://www.rotdoctor.com/products/cpes.html

oh they call it epoxy, thinned with solvents for penetrating wood.
What do you mean it is not epoxy?


CPES™ contains other precisely measured organic solvents which act as "carriers" and take the epoxy deep into the wood and then evaporate out over a period of time. The resin is carried through the soft or bad wood and into the top layers of the solid wood to seal and form a bonding surface no other product on the market can achieve.

Thorne
06-15-2010, 05:49 PM
I mean it is not epoxy. Something that contains a small percentage of epoxy is not the same as "epoxy" which can often contain from 60-100% epoxy solids. The enduring confusion on this topic mystifies me. 100 pennies is a dollar, and also money. 10 pennies is money but not a dollar.

Try Smith & Co. or other more reputable manufacturers for better info...

Todd Bradshaw
06-15-2010, 07:18 PM
Well, the ammonia/water scrub on the varnish can is clearly aimed at removing amine blush from cured epoxy resin. It's actually somewhat out of date as it was shown years ago that the ammonia wasn't really needed and didn't do anything a scotchbrite pad and water alone wouldn't do. However, CPES, being highly diluted with solvents, most likely doesn't blush and also can't seal the wash water out the way regular epoxy resin does. Washing your CPES surface with water, as if it was normal epoxy resin, is probably going to end up with water down in the wood between the CPES and varnish - which isn't good. I suggest that you ignore the varnish can's directions unless you happen to be varnishing over regular epoxy resin. If you're varnishing over CPES, follow the CPES directions and do not introduce water into the equation.

sdowney717
06-15-2010, 08:11 PM
http://www.smithandcompany.org/CPES/index.html
Smith says it creates "epoxy" impregnated cellulose, but I wont argue any further on this subject.

A Solvent and epoxy mixture, not magic goo but it works good.


Clear Penetrating Epoxy Sealer™ (CPES™) consists of a tough, flexible resin system in a solvent blend



When repairing wood that has mild dry rot, the CPES will migrate along the abnormal porosity which dry rot fungus creates within the wood, as long as it continues to be fed in. Impregnation of wood with CPES changes the cellulose of wood (which fungi and bacteria find tasty and easily digestible) into epoxy-impregnated cellulose which resists further attack by fungi and bacteria while reinforcing the wood, accomplishing restoration.

emf
06-16-2010, 09:44 AM
Hey tapsnap, how goes your faering project? We need some pix.

lagspiller
06-16-2010, 01:53 PM
He mentioned that he was going to have to slow down. In addition to winter being boat building time, I think he might be out looking for wood...

lagspiller
06-16-2010, 02:01 PM
I didn't use CPES, but instead thinned the hell out of Epoxy. I used Xylene and a touch of Denatured alcohol.

That was interesting. Can you be a bit more specific than 'hell' regarding the measure for how much thinning? Epoxy and equal amout of xylene, for example?

xtiffer
06-16-2010, 03:19 PM
I have been using Wood Impreg 120 which is a 2 component high gloss
clear epoxy-polyaminoamide penetrating sealer for wood and composite.
Very user friendly and recoatable without sanding. 3 coats give the perfect base for any varnish job.
As with any epoxy it has no UV resistance so varnish on top essential.
I normally use 5 coats of 2 part polyurethane varnish and the end result looks like 20 coats of Epifanes.
Not sure if it has crossed the pond yet however.
Cheers,
Chris

BrianM
06-16-2010, 03:40 PM
That was interesting. Can you be a bit more specific than 'hell' regarding the measure for how much thinning? Epoxy and equal amout of xylene, for example?


This is the thread where it was discussed in detail:

http://forum.woodenboat.com/showthread.php?t=85032&highlight=epoxy

I tried both 2:1 (Solvent to Epoxy), and 1:1.

Since its been a year, I honestly don't remember which one I used, though I tend to believe its the 2:1 formulation to allow maximum penetration/migration.

Best to experiment with the wood you are trying to seal, and the epoxy you have access to.

tapsnap
06-16-2010, 05:59 PM
I just put on the first coat of varnish. Thanks for all the advice!

http://www.danieloates.com/dory/justvarnished1lowres.jpg


http://www.danieloates.com/dory/justvarnished2lowres.jpg

georgel
06-16-2010, 07:58 PM
Just my prejudice. I would not have any confidence in urethane on wood. I have seen it peeling off in sheets. As to urethane over solid epoxy I have no experience. But I wouldn't use it on general principle. besides its ugly.

Sailor
06-16-2010, 08:19 PM
Nice looking work you have there. I just can't pass by a nicely finished bit of wood.