How to Apply Varnish to Unfinished Wood
Applying varnish directly to unfinished wood produces a durable, clear finish through which you can see and enjoy the natural beauty of your wood and its grain patterns. In fact, stains and other colored finishes serve mostly a decorative purpose unless they contain a varnish component such as polyurethane. Two or three coats of varnish protect unfinished wood against everything from spilled coffee on a tabletop to heat, precipitation and wind on outdoor trim. You do need to prepare the wood by cleaning and sanding it before you actually apply varnish.
Replace any sections or panels that have black knots or knots with cracks in them. Sand the entire wood surface to be varnished with fine sandpaper or a sanding block. Use an electric palm sander if you have one available. Sand in the same direction as the grain on the wood.
Wipe the sanded surface with a soft, dry cloth and then wipe it again with a tack cloth to remove all sanding dust.
Apply an even coat of oil-based or water-based polyurethane or spar varnish to the sanded wood with a natural-bristle brush. Allow the varnish to dry for at least 12 hours. Clean your brush with mineral spirits for oil-based finishes or a soap and water solution for water-based varnish.
Lightly hand-sand the varnished surface. Wipe it with a tack cloth. Apply a second coat of varnish with a natural-bristle brush. Clean your brush as soon as you are finished. Allow the surface to dry for 12 to 24 hours before sanding again and applying a third coat if desired or before using your varnished furniture.
Things You Will Need
- Fine sandpaper or abrasive pads
- Hand-sanding block or electric palm sander
- Tack cloth
- Polyurethane or spar varnish
- Natural-bristle paintbrush
- Mineral spirits
- Use an interior-exterior varnish even for indoor furniture. It protects far better and requires less maintenance than an interior-only varnish or furniture varnish.
- Keep all varnish and mineral spirits away from children and pets. Store oil-based varnish far from flames or extreme heat.