Golden Advice
There’s nothing prettier than freshly varnished exterior wood.
Here’s how to achieve perfection.
Opening a new can of varnish always reminds me of the rewards of working on wooden boats, of addressing the mahogany and teak trim with a fresh coat of liquid gold. Getting that glow starts long before the first brushstrokes take effect. It’s all about preparation.
I have always been a big fan of single-part varnish. Formulas range from fast-dry varnish—ideal for multiple coats in short order—to high-solid, tung oil coatings that offer ultraviolet protection from the sun for season-long protection. Many new boats are delivered with expensive, two-part clear coatings on toerails, moldings and other trim, but I prefer the cost and mileage I get from a single can. For my DIY projects, it is a feasible, lasting and economical choice.
Applying a fresh coat of varnish is a simple task, but if you are thinking about two-part coatings, be forewarned about trying to apply a two-part, cross-linked formula over an existing single-coat varnish. Doing this is likely to lift the previous finish, creating an epic mess. Completely removing the old varnish is necessary for achieving the best results.
Start with a cleanly prepared substrate. Varnished wood in good condition responds well to a thorough sanding and a fresh topcoat. But before opening the can, do a complete and detailed inspection of the existing finish and the wood beneath it. Areas that appear slightly crazed can be saved, but fractures in the varnish may have allowed moisture to wick its way into protective layers of the finish, as well as into the wood underneath. Those spots may need more than a simple sanding before proceeding.
A spot priming coat may be necessary to cover worn or scarred finishes for the new topcoat to look and protect wood as intended. Scout out any cracks between trim joints, missing plugs or surface chips in the finish. Any dark spots or blemishes in the wood indicate the need for more sanding and, in some cases, bleaching, or complete removal before spreading the fresh varnish.
I have used liquid removers, heat guns and scrapers to reach the bare substrate. Some imperfections, such as gouges, can be repaired while saving the rest of the trim, but more labor is involved. Famowood, a wood filler, dries fast and is easy to sand after filling any voids. It also will accept oil-based stains, a helpful characteristic when varnishing red or brown mahogany.
Varnishing is a labor of love. I keep after the woodwork three of four times a year to prevent major problems from developing, especially in my South Florida watering grounds. True success is predicated on a simple truth: Whatever coating you select for the job, the results will only be as good as the surface to which the coating is applied. Shortcuts or cheating on the necessary labor to prep the surface will reveal the truth in due time.
A sanding block works great with flat and wide surfaces, but I am a proponent of using 220-grit sandpaper for most of my trim work. I do mostly hand-sanding. Wrapping my fingertips with masking tape allows better control and encourages thorough sanding without leaving deep scratches or minute grooves in the existing finish. For tight corners, wrap a piece of sandpaper around a 1-inch putty knife, and then coax it into narrow spaces. After the first round of sanding, I wipe the surfaces with a white cotton cloth and either denatured alcohol or mineral spirits, followed by a swipe with a tack cloth for lingering dust.
Careful taping is important to protect surrounding areas from excess varnish. I use 3M’s blue weather-resistant tape, which can remain in place overnight or longer to allow for two or three coats of varnish with ample drying time between each pass. I have a favorite badger-hair brush with a tapered chisel edge that I use for most trim varnishing, although I have used foam brushes for touch-up work.
Don’t shake the varnish can before opening it. Shaking the can may form bubbles that are difficult to brush out. Also, pour the varnish you need for each project through a strainer into a smaller container to avoid transferring dust or grit. Unused varnish from each project should be strained before pouring it back into the can.
In cool or hot weather, varnish may need a splash of thinner or Penetrol for easier brushing with less drag and lap marks. A capful of thinner or mineral spirits poured into the remaining varnish in the can will prevent the contents from skimming over or hardening on the shelf.
When varnishing new wood, or wood that has had its previous coatings totally removed and is freshly sanded, thinning out the first coat will properly fill and seal the pores, serving as an effective primer for subsequent coats of new varnish. For a smooth, brushless finish, the trick is to maintain a wet edge as the varnish is applied.
Being right-handed, I work from right to left, applying the varnish and then stroking the brush lightly to the right. This way, I am moving away from the just-varnished teak, and I avoid bumping into anything wet.
When doing half round or batten trim, you have to develop a pace where the brush hits the bottom edge first, then the top and, finally, the front. With a smooth pass, you will have enough varnish to cover all three levels in one final swipe. Move to the left and repeat, bringing a fresh brushful from the dry surface to the wet edge.
If you notice that the surface you just passed appears dry, keep moving. You can fix that on your next coat. Trying to correct your miss can lead to too much varnish over that spot. The excess will bubble as it dries, requiring more sanding before the next round.
Unlike two-part clear coatings that cure chemically, single-can varnish dries as the solvents in the formula evaporate. It dries faster in warm weather, and slower when it’s chilly. Allow ample time for the varnish to harden before lightly sanding.
A light touch with the sandpaper is all that is needed to provide enough tooth for the next coat, producing a finish your dockmates will admire.
