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Get Your Shine On: Top Varnishing Tips for DIYers

A great varnishing job is a blend of smart preparation and time-sensitive application. Here's the right way to do it.
web_varnish brightwork

Brightwork maintenance is a regular chore that delivers instant gratification. Whether it is a transom, a toerail or half-round molding on the cabin side, a fresh coat of varnish on teak or mahogany restores beauty and adds durability.

I prefer single-part varnish because it is foolproof, less expensive than two-part mixtures, and ideal for DIY projects since the workload can be broken down into a schedule that suits you best. But whatever varnishes you use, the single most important rule is surface preparation. Varnish will only be as good as the surface to which it is applied.

More coats are not necessarily better, either, because varnish applied too thick can wrinkle, or it can peel off in sheets if the previous layer provides inadequate adhesion. It’s important to recoat before the surface breaks down, typically indicated by a crazing of minute trails under the existing finish.

When you wash your boat, always inspect the brightwork’s overall condition. Dark streaks or spots indicate that moisture is present and wicking its way toward the wood underneath. Yellowing indicates a break in the film, possibly the location where the moisture is entering, or even wood that has begun to decay. Anywhere that you have a joint, seam or accessory fitting (such as a stanchion base) demands regular scrutiny. A missing plug or bung that is supposed to hide a fastener in half-round trim or a toerail also creates a moisture entry point. Merely stroking varnish over dubious sections will likely do more harm than good, since the coating will lock in moisture that’s already present, helping it to permeate the existing finish.

When the task is to refresh a finish that is in good condition, wipe the surface with a clean cloth dampened with a suitable thinner, preferably of the same brand as the varnish you choose to use. This step will remove dirt, grease and grime, and make it easier to sand with less dust-clogging debris. Use semi--weather-resistant blue masking tape to frame the wood that will be varnished and to prevent the coating from spreading onto the surrounding substrate. A medium 220-grit sandpaper should be sufficient to knock off any gloss; avoid making more work for yourself with a coarser grit. The goal is to prep the surface with enough “tooth” so the fresh coats bond securely.

Most trim work can be hand-sanded, and you can save your fingertips by wrapping each one with the masking tape. I generally cut, not tear, my sheets of sandpaper in half and then fold each half into thirds for half-round moldings. I use a sanding pad or a block of wood wrapped in paper for toe and cap rails. Synthetic pads are also useful.

The key to thorough sanding is slow, steady and evenly applied pressure on the wood. You want to scuff up the finish, not remove it. Be careful not to sand through the edges or corners; a light pass is usually all you need. Replace the paper frequently, but save the used pieces for working areas around fitting bases, cleats and the undersides of handrails. Wipe each sanded section with a tack cloth, or vacuum up the dust, and then wipe the area with a clean cloth that’s dampened with thinner.

I am a fan of badger hairbrushes for all my varnish work. The bristles are hand-cupped and chiseled, and they carry a load of varnish that allows me to flow it evenly onto the surface with minimal brushing while avoiding runs and holidays, or missed spots. Avoid cheap throwaway brushes, which will litter your efforts with bristles as they fall out of the brush. I also avoid foam brushes because they spread the varnish instead of flowing it, a problem that results in less coverage, protection and gleam.

While the preparation is labor-intensive, the actual varnishing stage is about skill—which takes time to acquire. You need to appreciate a number of variables including weather, humidity, temperature, time of day and the suitability of the varnish itself. You also need to develop a technique. Being right-handed, I always work from right to left. This approach allows me to hold the varnish in my left hand and brush with my right while maintaining the wet edge needed to create a solid, consistent film of varnish. I stroke my last pass into the wetted surface as I move to the left, and then I continue onward. In addition, by moving away from the wet varnish, I won’t accidentally touch it.

Because 90 percent of the work in varnishing is preparation, you can usually get a second coat of varnish on the next day by leaving the blue tape on overnight. If the first coat takes a light sanding easily without clogging up the paper, then the next coat will go on quickly. Allow that coat to dry thoroughly, and then pull off the tape and get ready to accept the compliments from your dockside neighbors. 

10 Varnishing Tricks and Tips

Single-part varnish formulas have distinct purposes. A high-solid formula is best for top coating, since it usually has good UV protection and is long-lasting. But its drying and recoating time is longer than other formulas. Sunlight is the killer of all varnish jobs, so you want that UV protection to last. Fast-drying varnish formulas allow you to apply more than one coat a day, but for best results, add a top coat with a high-solid formula.

Never apply varnish out of the can. The brush will allow dirt and dust to contaminate the varnish inside the can, and you will be disappointed with the dust you see left behind in your work. Pour out what you need through a throwaway strainer into a small container and work from there.


Before you close the lid on the varnish can, pour one capful of thinner over the varnish. This thin layer will prevent air in the can from drying out the varnish. Avoid storing varnish in high-temperature areas. Also use the thinner for cleaning your brush.

Varnish is generally ready to use right out of the can without any thinners. However, Penetrol can be added in small amounts to enhance brushing and reduce brush drag to eliminate lap marks.

Unlike paint, varnish should not be stirred. Stirring creates bubbles that may be difficult to brush out. If you add Penetrol or a dash of thinner, gently swirl it into the varnish.

If you notice a missing spot or holiday in what you have varnished, leave it alone and get it on the next coat.

Spot-prime areas that need additional protection such as bare wood, chips or scratches. The spot coat will build up protective layers. Sand lightly after the area dries to feather in the surface, and apply multiple top coats to seal and protect.

Chips or nicks in your brightwork can be sealed and protected with clear nail polish until you can do a proper sanding and varnish job.

Watch the weather when you want to varnish, and note the forecast for the following 24 hours to be sure the varnish will have enough time to dry thoroughly. The prep work can be done anytime, but the varnish-application period is critical.

Protect your varnished brightwork after washing your boat. Dry the woodwork with a clean towel or chamois. Water spots left to dry under the sun can heat up and do a number on the finish.