Varnish Details

Revealing some of the secrets of the best varnish finishes
In their hearts, the owners of boats with traditionally varnished exterior brightwork know full well that they’ll have to rub down the varnish every year—without fail—and apply three new coats. But, human nature being what it is, they often procrastinate, claiming that the existing finish is good for at least another couple of months . . . and perhaps a whole season.Such self-deception can be short-circuited by an easy test. Here’s how to tell when your old spar varnish needs to be freshened. Wash the work thoroughly with fresh water to get rid of all grime. Wet an old piece of terrycloth toweling and drag it across the surface of the varnish. If the water left behind forms beads, the varnish is still in good condition. If the water sheets, or lies in flattish streaks, it needs immediate attention.The first step is to degrease it with a rag dipped in mineral spirits or denatured alcohol. Then sand it down using a fine-grit paper. Before varnishing, wipe the sanding dust away with a tack cloth dampened with varnish thinner. Don’t work outside when it’s too hot, too cold, too damp, or too windy. Choose your varnishing days carefully.Some varnishes need to be stirred gently. If so, that instruction will be in the fine print on the can. But be careful not to be too vigorous, or you’ll introduce bubbles that your brush will transfer to the work. Stirring usually isn’t necessary.Pour varnish from the can through a fine filter of cheesecloth or an old pantyhose into a small container with a thin collar of cloth rag tied near the top to catch drips, and work from the container. Flow the varnish on— don’t scrape it on too thin—using a throwaway foam brush for the first coats. Apply the finishing coat with the finest natural bristle brush you can afford.You don’t need to sand down between the first three coats if you apply the next coat between 10 and 24 hours after the previous one. At that stage, it will be dry enough for overcoating but still “green” enough to form some chemical links with the new coat. After the third coat, lightly sand between each coat—just enough to remove the little specks where you varnished over dust and to scuff away the shiny surface. Use 220-grit dry paper between coats or, for a mirrorlike finish, 360-grit waterproof paper dipped frequently in fresh water.During the sailing season, keep an old nail-polish bottle filled with spar varnish. Apply it to small scratches and abrasions in your brightwork before water has a chance to soak into the wood and discolor it.See also Brightwork; Varnishing.