How to Varnish With a Foam Brush

Finish-sand the piece you will varnish with 220-grit sandpaper.

Remove the sanding dust by vacuuming the piece. Lightly wipe a tack cloth over all the surfaces you will varnish.

Strain varnish into a clean mixing cup using a paint strainer. Thin the varnish with equal parts mineral spirits and varnish. Mix enough thinned varnish to apply one sealer coat to your piece.

Apply one sealer coat to your piece using a foam brush. Begin your sealer coat application by dipping the brush into the thinned varnish about 1/2 inch. Raise the brush out of the varnish, allowing the excess varnish to run off the brush. Brush the thinned varnish onto the piece, ensuring the brush strokes align with the wood’s grain. Apply an even coat over the entire surface and allow your varnished piece to dry overnight.

Sand the dry sealer coat with 320-grit sandpaper.

Remove the sanding dust with a vacuum and wipe a tack cloth over all the surfaces.

Apply the finish coats using either varnish thinned 25 percent with mineral spirits, or use full-strength varnish. Thinned varnish does not cure as quickly, which allows more brushing time. Strain the varnish with a paint strainer just before you apply your finish coat. Carefully apply your finish coat, and lightly drag the foam brush’s tip across the area you just varnished. Allow the varnish to dry for the recommended amount of time.

Sand with 320-grit sandpaper between coats. The varnish is dry enough to sand if you see a powder when sanding the last coat. Remove the sanding dust with a new tack cloth. Apply additional coats of varnish as desired.