Varnish Problem

In the last few weeks I have had inconsistent results varnishing epoxy (System Three) coated boat components. I am building a 16 ft. Mckenzie Drift Boat and have varnished the front deck; two seat frames and several other internal components. Several times the varnish remains tacky/gummy and the only result I can find to work is to scrape it off, sand it and start over. Getting tired of this. I am looking for an answer or a tip or two.
I built a stripper canoe a few years ago and had zero problems then with the same varnish…

Here’s what I have been doing. I have been using Epifanes Gloss Varnish. The varnish was from an unopened can that has been stored in my heated basement. It was new in 2006.

Preparation, after a light sanding with 220 I brush off the dust, wipe it with a white terry cloth towel, then wipe it again with white paper towels with 70 % rubbing alcohol. Mixing the varnish in washed plastic bowels (cool whip, butter, etc). I run it through a paint filter from the can into the bowel, and added 10-15% thinner (Epifanes Brush Thinner) and stir until well mixed (like mixing epoxy).
I am using a fairly inexpensive brush. The second time varnishing the deck I added a second coat full strength and it never hardened in a week.
Any body out there have any ideas?????

phil w.

 

There is a good chance that it could be amine blush or sweat that wasn't removed from the 100 solids epoxy. Cobalt is used as a drier in many single pack products like varnishes and enamels, amine inhibits cobalt and doesn't allow the product to through dry. Amine blush or sweat should be removed with fresh water. Alcohol, solvents, etc. will not remove the blush.

If the epoxy surface feels like it has a thin coat of oil on the surface after the epoxy has cured, the surface has blushed and needs to be washed with water before sanding, painting, varnishing.

 

Mike,

Thanks for the quick reply. You hit the nail right on the head. I am familiar with Amine Blush, I just lost my mind and forgot to remove it with soap/water and just sanded the epoxy prior to applying the varnish. Looks like I have created more work for myself.
I had no problems when I varnished the hull as I had washed it inside and out, duh!

Thanks again,

phil w

 

Phil,

I think we've all forgotten a step in some process at one time or another, I know I have. Good luck with your boat and finish.

Mike

 

I reread your original post, the other thing I would caution is the "stirring or mixing up" varnish. Varnishes should be gently stirred, anytime they are mixed or stirred like you would an enamel topcoat you stand a high chance of introducing bubbles. The bubbles will not dissipate during the application and will show in the finish.

Straining is a good idea, and for the optimum finish do not pour used varnish back into the can, try not to pour and thin anymore varnish than is needed for the job.

 

Amine blush will not stop the cure of an alkyd over coat, such as varnish or paint. Amine blush is a wax like substance that as you'd imagine prevents over coats from sticking well, but it doesn't usually alter cure rates.

Of course you stir varnish, though as Mikent suggested, it should be done fairly slowly, as to not create bubbles.

I think it's the brand of varnish you're using. Some alkyds can have it's cure affected over epoxy. As to which these might be, well it's often a crap shoot, without prior experience. What brand of varnish (is it really varnish) are you using?

 

There are exceptions to almost every rule, but if an enamel or varnish incorporates cobalt as the main drier it will not cure if it comes in contact with amine blush. Amine blush can also migrate through some single pack primers and cause both detachment of the primer and topcoat as well as cause "yellowing" of the topcoat.

As a rule, 100 solid epoxies should always be scrubbed or washed with freshwater before sanding or over coating. And again there are exceptions to that rule, an example of,that would be using peel-ply during the layup

 

As I stated in my original post, I used the varnish from an unopened one Liter can of Epifanes Clear Gloss Varnish. The vanish was the last one of a case of 6 cans I purchased in 2006. I used up the rest of the varnish on my stripper canoe in 2006 and other projects.
As I mixed it with the thinner I was careful not to introduce any bubbles into the varnish. My reference to mixing like mixing epoxy was in reference to taking a couple of minutes of mixing and scraping the sides to assure the thinner and varnish was thoroughly mixed.
On the Drift Boats hull that had been washed, eliminating the Amine Blush, both the inside (the first coat) and outside (the first two coats) the varnish dried overnight.
It was the boats major interior components that I have had a real problem with. Just today I scraped the varnish off the front "guest" seat and will be varnishing it tomorrow. I'll post the results ASAP.
I still have a real problem with the front deck as the varnish is really stickey and has accumulated a lot of foreign material the last few days. I scraped it once and re-varnished it last week to it's current condition. I am also wondering if a solvent would remove the varnish with out affecting the epoxy? Anyone got any advice as to what solvent might work; thinner, acetone, laquer thinner, etc????
Thanks for all the previous replys, they are appreciated.
phil w.

 

Thinner is the solvent for that Epifanes, so I'd use that. Epoxy is resistant to most solvents and is commonly used because of it's chemical resistance as a paint. The only thing NOT to put on it, is dichloromethanes - found in pre 2010 paint strippers (in EU) which will attack it and polyesters.
Wipe clean with thinners then sand or wire wool surface and put the fresh stuff on. I've used 12 year old 2k paint (with fresh hardener) without problem, but not one packs that old. I have run into an epoxy/Epifanes (one pack) problem where the varnish did not/had not keyed into the epoxy. It was fresh stuff too when applied.