To Varnish or Not? Page 2
You’d think that modern science could come up with something better than tung oil and phenolic resin to protect teak, but this hasn’t happened yet. The fact that boat manufacturers are now turning to plastic teak to deliver the appearance of wood without the maintenance says a lot. In general, the alternatives to oil and resin—be it teak oil, sealer or varnish—are synthetic coatings that are easy to apply and dry to a low- or no-gloss finish. These coatings tend to breathe, so they do not blister or peel, but their ability to withstand exposure 24/7 is on par with an oil-based finish. If you like an oil finish, you’ll find a synthetic coating is just as easy to apply, less prone to darkening, and slightly longer lasting.
Sailors who love wood-trimmed boats but hate the maintenance sometimes resort to brown paint. If the color selection is right, this expedient can be hardly noticeable to casual observers. To others, of course, painting teak is a travesty, but paint sets the bar for durability. The reason is the pigment, which essentially shades both the wood and the finish itself.
A number of “marine” wood finishes, whether resin- or polymer-based, try to improve their durability by including stain or pigment. This ploy is effective, as translucent finishes outlast transparent ones, all other things being equal. The more opaque a finish, the longer it lasts, but the poorer job it does of bringing out the natural beauty of the wood. Whether to use a pigmented finish is, of course, a matter of taste. Sikkens Cetol products are popular among sailors who either like the look or view it as an acceptable low-maintenance alternative to varnish.
Modern technology (and in some cases “boatyard ingenuity”) has given us some two-part finishes that do outlast spar varnish in the marine environment. Just as varnish is oil-based paint without pigment, two-part wood finishes are essentially polymer topside paints without pigment. The life of a clear two-part linear polyurethane finish might be measured in years rather than months. And as an added bonus, two-part urethanes properly applied are even glossier than spar varnish.
Why haven’t these miracle coatings replaced varnish? Because of the consequences of coating damage or failure. Brightwork can and does suffer damage. With varnish, a little skillful touch-up can make a ding or blister virtually disappear. Spot repairs to a polyurethane finish are likely to be as conspicuous as the damage you’re trying to hide.
Widespread failure is an even bigger catastrophe. Hard coatings, whether single or two-part, can be lifted off wood hydraulically by moisture. With varnish you can do a spot repair or strip the wood and start over. Stripping varnish is less fun than putting it on, but with a well-handled heat gun and a scraper (see “Down to the Bone,” p.64) you can get it off readily enough. Two-part coatings are hard to repair, so widespread failure usually means starting all over. Here is the down side of the toughness of a polymer coating. Stripping off undamaged polymer is a trying experience that many are unwilling to repeat.
The other two-part finish, a boatyard innovation, is varnish over a base coat of clear epoxy. The idea here is that the epoxy adheres better than varnish and is less likely to separate from the wood. Epoxy is, however, prone to UV damage, so the overcoat of varnish provides essential UV protection. This type of finish can significantly outlast varnish alone, but unlike a two-part polyurethane finish, it needs frequent recoating. Because of the risk of UV damage to the epoxy, it is even more essential to keep the varnish fresh. The surface coat of varnish can be repaired and renewed easily, but the epoxy undercoat will make dealing with a widespread coating failure much more difficult.
An epoxy undercoat can also provide a superior base for a two-part polymer coating, yielding a tough, deep finish that should not require any maintenance for a couple of years or more. You must be certain, however, that your top coat has sufficient UV screening to shield the epoxy, or you will discover that the negatives of this combination are cumulative.
The Unvarnished Truth
No sailor needs to varnish the wood on his or her boat, particularly if it is teak. There are no safety implications, no performance benefits, nor even a unique benefit to the wood itself. We varnish because we like the way it looks, the way it makes our boats look, and perhaps even the way it makes us look. If this doesn’t matter to you, you should probably coat your wood with something else. But if you really want to turn heads with your brightwork, age-old spar varnish still provides the best combination of beauty, durability and maintainability. Unfortunately, the act of varnishing remains as odious as ever. It is the price you pay