Varnish is the most popular marine wood finish because it showcases the beauty of the wood grain and produces the highest gloss and greatest depth. Here are some expert tips to help you achieve beautiful, long-lasting results.
- Sand and varnish with the grain to prevent scratches—which can be visible even through several coats of varnish.
- Keep the dust down by vacuuming your work area first, then spray water on the floor or ground with a water-filled spray bottle.
- Stir varnish gently, do not shake the can of varnish. Aggressive stirring or shaking can introduce bubbles, which are bad news.
- Pour varnish through a strainer and into a separate container to filter it and prevent contamination in the can. Pour only the amount you will use in any one application.
- When varnishing outdoors, avoid working in direct sunlight. Also, time your application so a fresh coat has adequate time to skin over before dew sets in.
- When varnishing indoors, apply varnish in adequate light so you can see skips and holidays. Aim a light source horizontally across the varnished surface to make any skips stand out.
- If brushing, dip less than 1/2 the length of the bristles into the varnish so you get more varnish at the tip, where it’s needed.
- To avoid brush marks, maintain a wet edge by brushing the newly applied varnish into the area just previously applied. A feathering motion, applying less pressure as you lift the brush from the surface, will help to eliminate brush marks.
- To remove small bubbles on the newly varnished surface while brushing or rolling & tipping, make a final pass over the area very slowly, using very light pressure.
- Watch for drips on vertical surfaces.
- Avoid trapping solvents beneath the varnish by applying varnish thinned as directed by the manufacturer. If varnish is too thick, it can sag, or orange peel, and not cure properly.
- Leave trapped dust specs or bugs in place till the varnish tacks over. You can sand them out between coats.
- Sanding between coats: Sand lightly with fine sandpaper. Generally, between coats, use 320-600 grit. After a coat of varnish has dried, if the coat looks really good, use a 3M Scotch-Brite™ pad (not sandpaper) to scuff the surface lightly. If the previous coat has slight imperfections, sand lightly with 320-400 grit paper to even it out and allow the next coat of varnish to achieve a sound mechanical bond with the surface. Sand only as much as you need to. Use a gentle, even motion to remove any peaks or bugs, and most importantly, to avoid sanding through the previous coat. When sanding between coats, the residue should be a fine powder. If it’s not, stop sanding and allow the varnish to cure completely. After sanding and before applying the next coat, vacuum then tack, and wipe with a lint-free rag wetted with mineral spirits to remove impurities. Allow the solvent to evaporate.
- Clean brushes thoroughly after each use.