Novice boatbuilder needs varnishing advice.

[GymBob]

I am currently building my first boat and need advice about applying varnish over epoxy. I have applied 3 to 4 coats of west system epoxy to all of my surfaces that will be brightwork. My question is what type and how many coats of varnish are required for proper UV protection?

[rwatson]

I hope people are going to say "any high quality marine grade, UV inhibited Polyurethane satin varnish", as that is what I am about to use.
I just noticed in the side of the can that high buildup of varnish should be done in the High Gloss version, with the final two coats in the Satin that I was recommended.
A while ago I started a thread on brightwork using West Systems Epoxy. Is that what you are using ?

[PAR]

Varnish isn't the same as polyurethane clear coatings, which sometimes are also referred to as varnish (though the word polyurethane will appear in the name somewhere).

Varnishes are usually composed of linseed, tung or walnut oil which is the oil aspect. A resin such as pine resins, balsam, amber (and others) which serve as a polyimide and a vehicle, typically turpentine (vegetable base) or mineral spirits (petroleum base) as the solvent.

Polyurethane is basically some organic elements tied to urethane.

Both of these clear coatings have UV inhibitors added to increase durability in outdoor environments.

All of the major brands of marine grade varnish are quite good. Some seem to "flow" better then others, while some seem to tolerate more abuse. Generally the polys will produce a harder coating, but can be difficult to repair and have difficulty staying stuck to wood that sees much moisture cycling. Traditional marine varnishes aren't as hard as the polys, but are easier to repair and can absorb more movement in the substrate.

Apply your first coat of which ever, thinned about 20% by volume, then your next coat be 10%, with the remaining coats as desired, with the finest brush you can find. Some have great luck with foam brushes, which do lay down a nice swath, but don't hold much material and can drip. If spraying, thin until you're not getting a stippled finish.

Work clean and carefully, with light sanding between coats.

[rwatson]

Varnish has long been the descriptive term for a clear finish - which is why Polyurethane 'fininshes' have the word varnish "in the name somewhere"
The initial thinning is the recomended way of doing timber - but the question is - onto Epoxy. The thinning will not have much effect for an already sealed surface.
West Systems clear finish has special consideration (and maybe others to) which is why I asked Gymbob about the brand of epoxy he has used.

[PAR]

Good catch Rwatson, I missed the epoxy part. He's correct, you don't need to thin the varnish or polyurethane when over coating epoxyed surfaces, unless you are spraying.

[GymBob]

How many coats of say "Interlux - Goldspar" do I need to apply. Interlux advises 5-6 coats on bare wood. I am thinking that number is intended to seal the wood as well as provide UV protection. Since the wood is already sealed with West System Epoxy can I do less coats for the same UV protection?

[rwatson]

By golly - it does say in black and white that you are using west system. It is must be my old age creeping up on me.
In the West Systems tech literature, the only recommended hardener to be used for clear finish is the 207, which is dearer than the epoxy you add it to!!! The 207 hardener is touted as being very compatible with clear finishes, but the other hardeners are not.
If, like me and it appears 90% of other users, you used one of the other hardeners (205,206) then you may need to check with the supplier that any varnish you use has been successfully used with West Systems.
Interlux is a recognised name, so I would expect no trouble. I was planning on about 3 coats myself, but I notice on a test section that the scratches from 80 grit sanding showed through the brushed on coat.
It may be that I end up with 4-5 for appearance sake, but for UV protection, unthinned varnish would want at least 3 coats, as they are very thin.
I am off today to buy a can of Gloss varnish in my no-name brand to use for a "build up" base, but I will finish off with Satin, which was recomended as the final coat. That should cover the worst of the scratches.

[PAR]

Varnish wears out with UV exposure. You need several coats to maintain a healthy undercoat of epoxy. In other words, if you apply 3 coats of varnish, in one year of direct exposure to sun light you may only have the thickness of one coat remaining (depending on climate). When you sand this for your touch up, you'll be getting into the base substrate. Ideally you want a reasonable base of clear coat so that prep for subsequent over coatings will leave this base intact.

The other West System hardeners will accept varnish or polyurethane over coats, but the result will be more amber color. The 207 is particularly clear compared to the other more amber hardeners.

[Kaptin-Jer]

You might want to look into Awlbright which is a clear or Awlspar which has a slight "varnish" tint. I have bought some but haven't used any yet. I have seen other guys in the yard use both with great success.

[Scott Carter]

I'll go along with Kaptin on the Awl-brite. Exceptional durability and it flows like butter. Proper thinning is madatory depending on your application process, and application over epoxy bases is commonly done; it's even more expensive than West or other epoxies.
Re. "How many coats?": The UV protection it will lend the vulnerable epoxy will increase with each additional coat to a point, but you should count on a minimum of 3 or 4, while Awlgrip recommends 10! As already mentioned by someone else, you want to avoid the wear of daily use finding its way down to the epoxy.

[LP]

I can't say that I have ever used AwlGrip so I can't compare it to what I use. I do have a fully bright finished epoxy encapsulated wooden boat. It was my first boat project. See the avatar. I started with hardware store varnish and decided that it was stupid to be using such a cheap varnish on such a hefty investment of time and money. I went out and purchased some Goldspar which was a fantastic inprovement over the other "stuff" in application and flow out. My source for Goldspar ran out of stock so I ended up switching to the more expensive Captain's Varnish 1015 from Petit. Hold you horses baby. I put it on with a foam brush and you could swear it was a spray coat. Night and day again over the Goldspar! It works so well that I haven't even considered using anything else. The only change I've considered is switching to the 2015 formulation as it has more UV inhibitors.

I put on a minimum of 6 coats three seasons ago and the areas that get heavy use (sidedecks) were in need or recoating this year. The other areas look to be fairing better and could actually make it another three seasons or more. My boat also lives on a trailer that lives inside when not in use.

In many ways, you're are going to get what up pay for with the finish that you choose. I can't compare durabilities of different products, but the application of Captain's Varnish is amazing (to me anyways).

[alan white]

I like Captain's very much too. The Goldspar (if I remember correctly) is a super UV formulation. It also comes a bit thick out of the can, and won't go on well without about a 5% reduction with #333 brushing thinner.
Captain's goes on right out of the can and I rarely thin it, and then only a small amount.
I see no difference, except in price, with Captains often on special for $23.00 or so and Goldspar up around $35.00.

A.

[LP]

I'm buying my Captain's at the wrong location. Where are you purchasing yours for $23 Alan?

[Kaptin-Jer]

I have tried all the high end varnishes. I found that I have a lot of problems with them especially when trying to varnish in the Florida sun. The one "varnish" that I keep coming back to is the inexpensive Minwax. It flows better that the expensive ones in hot weather, gives a very good gloss and last almost as long as the others. I feel that if I have to re-varnish every 6 to 8 months I'm not going to wast my money on the expensive stuff that might last 2 more months. I get a finish that always brings compliments. That is good enough for me.

[Jimbo1490]

Polyurethane is basically some organic elements tied to urethane.

The term 'polyurethane' is thrown around a lot but like the term 'epoxy' really just refers to the type of chemical bond or crosslink the final polymer has. Most any organic (contains carbon) resin or monomer can be 'converted' to polyurethane with the right isocyanate catalyst in the presence of other chemical helpers. The different starting monomers determine a lot about the final product, which in turn determines the final use, such as paints and coatings, adhesives, structural (rigid) foam, soft foam and etc.

For paints and coatings polyester resin (yes the same stuff), acrylic resin and even alkyd resin have been urethane-ized. For marine paints the polyester urethanes are the most prevalent (like Awl-Grip). Acrylic resin based urethanes dominate the automotive paint market. Imron among a few others actually starts with urethane resin.

It should be noted that linseed oil is known in the paint formulating biz as 'linseed alkyd resin', and could also be/has been 'converted' to polyurethane. Natural linseed resin (from boiling flax seeds) was long ago replaced in most paint/polymer markets by synthetic alkyd resin, usually with the name shortened to 'synthetic' enamel or alkyd enamel.