Varnish over Epoxy

[Porthandbuoy]

A couple of questions:

1) Is there a 'best' varnish to go over epoxy?

2) What's the recommended application method? Should I put the first coat on while the epoxy is still tacky? I don't see much point in thinning the first coat either.

Can anyone advise or put me right?

We're talking cockpit sole and tiller, so outside and exposed to the elements.

 

[Tranona]

Personally, I would not bother with epoxy in the first place, nor varnish on a cockpit sole. You don't say what your sole material is - but teak is best left bare or coated in Semco. Other timbers might be better with a porous woodstain such as Sikkens.

For the tiller, if you are after that "cabinet" shiny finish then conventional varnish - either single or two pot and spend the epoxy money on a canvas "sock" to cover it when not in use ie 99% of the time. Your finish will last just bout indefinitely.

 

[vyv_cox]

I'm not much of an authority on wood but I have read that epoxy on large wooden surfaces is not advisable. Its brittleness when cured tends to cause cracks when the wood deforms. I can vouch for this on my back gate which has epoxy coated plywood panels. Despite having multiple coats the water has got in within a few months.

 

[Pye_End]

Give the epoxy several days (if not longer) to fully harden (in the warm), then use a varnish with good UV properties - plenty of coats.

My preferance would be Sikkens UV varnish on top, but they don't make it now!

Did my washboards like this a couple of years ago and they still look excellent.

 

[oldsaltoz]

Give the epoxy several days (if not longer) to fully harden (in the warm), then use a varnish with good UV properties - plenty of coats.

My preferance would be Sikkens UV varnish on top, but they don't make it now!

Did my washboards like this a couple of years ago and they still look excellent.

Totally agree, just make sure you get a very high UV rating.

Good luck.

 

[Delfin]

I have used epoxy under varnish for many years in many applications and done correctly, it provides the longest lasting possible finish.

Start with penetrating epoxy over the bare wood. You can make this with regular epoxy thinned to the consistency of water with MEK, or you can buy it already thinned. It is critical that it be very, very thin. Apply up to three coats one immediately following the other - in fact, you can apply a coat over a section, then right away go back over it with fresh. When this has kicked off, apply another coat to make sure the wood is completely saturated.

Wait three days, then sand to remove furring only without heating the wood up with friction. This avoids gumming up the epoxy. Follow with 8 coats of high quality UV varnish - I have used Flagship with good results, although it is a little harder to work.

With this method I have gotten 5 years on spruce masts without touch up.

The key is to remember is that the epoxy has no UV resistance and will whiten and dull if exposed to sunlight, you you must keep varnish on it. However, using this method you will create a substrate for the varnish that will resist moisture penetration, which is death to varnish. If you have to go to bare wood following this treatment, it is no more difficult than if you never used the epoxy in the first place.

Using unthinned epoxy is possible, but very difficult to do right, and IMHO not worth the effort.

 

[Bosun Higgs]

West recommend a twin pack poly on top of epoxy. When I have used it, it has lasted way better than conventionals like Sikkens.

 

[davidbfox]

I am just doing varnish over epoxy for plywood cockpit locker lids, following forum advice last year. I could not find any suitable alternative to ply. I had thought there might be a plastic material. Hardwoods from Victorian wardrobes were also usefully suggested by forum members

Last weekend I varnished the new "marine" ply lids then left them in my garage. This weekend they are still very slightly sticky to the touch. The unvarnished (epoxy-only) side is not sticky, the varnished side is.

I used Rylard one part varnish thinned a bit with white spirit. I'm now not sure if it was the thinning or a mismatch between varnish and the epoxy that has caused the stickinees.

On the same session I used the same thinned varnish on previously varnished ply - no epoxy - and that has dried fine so I think it must be to do with the epoxy.

The garage is not heated, but I would not have thought that would cause a problem setting over a week.

I did not thin the epoxy as described in the post above.

 

[Lakesailor]

I had the same with a couple of rudders I made last year. It's likely that the epoxy wasn't fully cured before the varnishing.
Epoxy really needs above 15°C to go off. A local kit boat builder uses hot air guns to harden off epoxy if it's being awkward.

They eventually harden.

I used tun oil varnish over epoxy on my Heron for the decking to get a nice finish. Epoxy reduces the need for quite as many coats of varnish and makes scratch and ding repairs easier as the wood is protected.

 

[davidbfox]

"It's likely that the epoxy wasn't fully cured before the varnishing.
Epoxy really needs above 15°C to go off. A local kit boat builder uses hot air guns to harden off epoxy if it's being awkward."

That's helpful - thanks!

Dave

 

[prv]

A local kit boat builder uses hot air guns to harden off epoxy if it's being awkward.

Last year I used to use a normal domestic fan heater to help with fibreglass and epoxy at January temperatures. This year it seems to have mysteriously disappeared, so I bought a hot-air gun from Machine Mart to replace it.

I think the fan heater was actually better. The gun makes a small area very hot indeed (even on low setting) so I have to keep moving and tweaking it to avoid cooking either the epoxy or the surface it's on, and to get the whole area warm. The shape is awkward to set down and leave to get on with warming the work up while I mix the resin - I end up spending ages wedging and blocking it, and then it falls over (ready to burn something) as soon as I turn round. The fan heater, by contrast, puts out the same amount (or more) of total heat, but it's spread out across the whole work area so I can just leave it to work. And of course it has feet so will sit stably in many situations, and when it won't the square shape is easier to wedge in place.

Pete

 

[Porthandbuoy]

Tons of useful advice there folks; thanks. I particularly liked the idea of a sock of sorts over the tiller.

 

[Delfin]

I am just doing varnish over epoxy for plywood cockpit locker lids, following forum advice last year. I could not find any suitable alternative to ply. I had thought there might be a plastic material. Hardwoods from Victorian wardrobes were also usefully suggested by forum members

Last weekend I varnished the new "marine" ply lids then left them in my garage. This weekend they are still very slightly sticky to the touch. The unvarnished (epoxy-only) side is not sticky, the varnished side is.

I used Rylard one part varnish thinned a bit with white spirit. I'm now not sure if it was the thinning or a mismatch between varnish and the epoxy that has caused the stickinees.

On the same session I used the same thinned varnish on previously varnished ply - no epoxy - and that has dried fine so I think it must be to do with the epoxy.

The garage is not heated, but I would not have thought that would cause a problem setting over a week.

I did not thin the epoxy as described in the post above.

David, the epoxy will outgas slowly at low temperatures, and that is likely your problem. I don't know the Ryland product, but a semi-synthetic varnish like Flagship, or a catalyzed 2 part works well as long as the epoxy has well and truly gone off. The advantage of thinning the epoxy is that the wood fibers absorb the stuff, which greatly helps reduce black spotting if the varnish gets dinged, as well as stiffening the wood and making it more resistant to dings, as noted. I'd take the Ryland off and try another varnish. You'll probably be happier in the long run.

 

[xtiffer]

My way of using epoxy's properties is to use a product
designed for yacht spars: Wood Impreg 120 ( a clear epoxy primer)
followed by Seatop PU360UV ( a 2 part polyurethane varnish).
Just recoating a mast I did 3 years ago and all it needs ( other than chafing damage) is a 220 sand and a coat of varnish.
Tough, glossy and pretty all in one go.
Cheers,
Chris

 

[Harry P]

Thread info?

I am just doing varnish over epoxy for plywood cockpit locker lids, following forum advice last year.

I'd be interested in seeing this thread. Can kindly direct me to it?

Regards
Harry

 

[Amulet]

...The garage is not heated, but I would not have thought that would cause a problem setting over a week.

I did not thin the epoxy as described in the post above.

Although the technical data sheets ask for warmer, Gougeon brothers books says that they find that epoxy sets down to 7 Celsius. That is my experience too (using West System).

I have, however, tried to get it to set at a lower temperature - which sounds like your experience. The bad news is that in my case it then NEVER set properly. It was still sticky to the touch a year later. I hope I'm wrong about yours!

It's best to warm both the substrate and the resin. I bring small bits like cockpit seat lids in and stand them by the AGA. (This stimulates some marital strife.) I stand the can of resin in warm water - but be careful - you don't need to heat it up much to reduce the pot life to a few minutes.

 

[davidbfox]

I'd be interested in seeing this thread. Can kindly direct me to it?

Regards
Harry

http://www.ybw.com/forums/showthread.php?t=245106

 

[davidbfox]

David, the epoxy will outgas slowly at low temperatures, and that is likely your problem. I'd take the Ryland off and try another varnish. You'll probably be happier in the long run.

Thanks for all advice. I did another layer of epoxy after sanding the varnish off. That has set hard and the next varnishing seems fine.

I post this to record the lessons learned for future searchers after knowledge;

1: warm the epoxy and the wood in wiinter
2: if still sticky next day it's going to stay sticky forever so do it again
3: two part varnish is recommended