All About Varnishing Your Boat

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Few things evoke the romance of sailing better than varnished wood. But few things are as unpleasant as the act of varnishing. photo by Photos 12/Alamy

Few things evoke the romance of sailing better than varnished wood. But few things are as unpleasant as the act of varnishing. photo by Photos 12/Alamy

Dorothy Parker once famously remarked: “I hate writing; I love having written.” I feel the same way about varnishing. Nothing flatters a boat more than the glow of well-varnished wood, but to bask in that glow, someone must suffer through the process of preparing the wood and applying the varnish.

Almost all woods other than teak will weather and eventually rot if not protected from the elements. Paint is the most effective protective coating, but if you paint wood, all you see is paint. Varnish protects wood without hiding its inherent beauty; ten coats of glossy varnish can transform a merely interesting piece of wood into something achingly beautiful. Dorothy Parker’s sentiment applies: everyone loves varnished wood. It is the varnishing we hate.

Unfortunately, varnish is your only choice if you want to protect exposed mahogany without painting it. As for teak, it can stand the exposure, but due to pollutants in the air, it will more likely turn black than silvery grey if not treated. You can bleach and scrub it back to its original golden hue, but each scouring removes a layer of wood. Exposed screws and popped bungs in teak woodwork are nearly always due to excessive cleaning, not weathering.

What Is Varnish?

Varnish is essentially paint without pigment. It is broadly defined as a transparent hard coating, “hard” being the key word. It is the solid left behind when a liquid mixture of oil and resin dries. In traditional spar varnish, the oil is tung and the resin is phenolic. Today there are many other formulations on the market, but no other transparent single-part coating is more durable in the marine environment than spar varnish.

Most sailors don’t care what’s in the can as long as it goes on easily and lasts a long time. Still, in deciding whether to embrace or shun varnish it helps to know that the can contains some kind of oil, some sort of resin, a quick-evaporating solvent, maybe a drier to accelerate the process, and an additive or additives that boost ultraviolet protection.

Over the years I have tried several different varnishes, most to good effect. I do have a favorite, but will not name it here lest I seem unenlightened to devotees of other brands. I will offer this: you can’t go wrong in terms of aesthetics and durability if you select a spar varnish that has a tung oil and phenolic resin base along with UV inhibitors.

Meticulous preparation is a key ingredient of any good varnish job. Photo by Billy Black

Meticulous preparation is a key ingredient of any good varnish job. Photo by Billy Black

Easier Alternatives

Because varnishing is such a pain in the transom, chandlery shelves are crammed with other products promising similar protection with less effort. Paint sellers also offer an array of transparent wood finishes that are purportedly easy to apply. In fact, virtually all these alternatives are both easier to apply and reapply. Unfortunately, their durability ranges from fleeting to seasonal, with some notable exceptions.

Oil is the easiest alternative and the shortest-lived. The idea is that it restores wood’s natural oils, which, take note, sounds a lot like marketing for daily skin care products. Teak oils used to be either linseed oil or tung oil-based, with tung being the preferred choice, but you’re just as likely to find castor, palm, lemon and even synthetic oils in today’s chemical concoctions. Most also include resin (to extend the product’s life), solvent (to improve penetration) and UV additives.

Teak oil looks nice when fresh, but it washes away at sea or carbonizes and turns dark at a dock. Like any oil, it also traps dirt and fosters mildew. Teak oil rarely lasts more than a few weeks, and its lifespan declines in lockstep with your latitude. For teak decks, oiling can be the best alternative to bare wood, but when it comes to brightwork, the cooler, cleaner, and more overcast your environment, the longer your teak oil will last. In sunny climes, oil appeals only to those who prefer short but frequent maintenance sessions.

Sealers, sometimes called “treatments,” typically contain the same core ingredients—oil, resin, solvent and UV additive—but the ratio of resin to oil is higher. This is to prolong the product’s lifespan, and sealers on the whole do last longer than oil. But if you fail to maintain it properly, the additional resin makes prepping the wood for a fresh attempt more difficult. Sealers are best applied to fresh teak or to teak that has been freshly oiled. You can, if you like, concoct a perfectly serviceable sealer yourself by thinning down spar varnish by 50 percent with turpentine or mineral spirits.


High-Tech Finishes

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.

Woodwork like this cries out for many coats of varnish. Photo by Peter Nielsen

Woodwork like this cries out for many coats of varnish. Photo by Peter Nielsen

Adding Pigment

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.ADVERTISEMENT

Two-Part Alternatives

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.


Varnishing Tips for the Hardcore

  • Start with a perfect surface. Bleach with oxalic acid. Rinse heavily to remove every trace of acid. Sand smooth with 100-grit paper for teak, 120-grit for other woods.
  • Eliminate moisture paths. Moisture that gets under the varnish will lift it. All bungs should be set with varnish. Level-fill joints and cracks with epoxy.
  • Keep initial coats thin. Uncut varnish will bridge wood pores, leaving space for moisture. Thin the first coat 50% by volume—1/2 ounce of thinner to every ounce of varnish. Thin the second coat 25 percent, the third 10 percent.
  • Wipe off surface oil with a rag dipped in thinners. Just before varnishing, wipe teak down with an acetone-saturated rag to remove surface oil.
  • Use a foam brush. Foam brushes tend to keep you from applying varnish too thickly and they don’t spoil the finish with loose bristles.
  • Apply at least six coats. You can add additional coats later, but for complete protection you need at least six.
  • Wait 48 hours to sand. You need not sand between the first three coats (if your applications are within the recoat time), but all subsequent coats require sanding. No matter what the instructions say, 24 hours is insufficient drying time; allow at least two days.
  • Refresh early and often. Varnishing is like reefing; when you wonder if it’s time to recoat, it is.

Epifanes North America,

Flood Company/Akzo Nobel,

Interlux Yacht Finishes,

Performance Coatings,

Pettit Paint,

Smith & Co.,


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