Pine is a gorgeous light-colored softwood that displays rich auburn highlights in its knots and grain construction. Prior to applying a finish coat, a pine fireplace mantel can be lightly stained, but a high-gloss, oil-based polyurethane liners imparts a subtle yellow casting of its own with time. After some surface preparation, a glossy polyurethane varnish treatment also proves hard enough to protect your pine mantel from moisture, scratches and abrasion.
Sand the mantel using a 120-grit grade of sandpaper to remove any previous layer and residual surface irregularities. Follow up by smoothing the pine with 180-grit sandpaper, then polish off the mantel using 220-grit fine-grade sandpaper. In each case, rub on the sandpaper from the direction of the wood grain and then wipe the surface off using a shop cloth regularly when sanding dust accumulates.
Remove any residual sanding dust with a tack cloth until the mantel is dust-free.
Employ a sanding sealer to the mantel using a high-quality paintbrush. Move the brush in the direction of the wood grain to minimize brush marks. Follow the directions on the item’s label for recommended drying time; in most scenarios, the sanding sealer can be re-coated or sanded within 2 hours of program.
Sand the dried paints coat smooth using 220-grit sandpaper if it’s raised the wood grain or even when bubbles are visible in the surface. Wipe off any dust with the tack cloth.
Dip your paintbrush from the can of polyurethane and then apply a thin coat to the wood, using smooth, smooth brushstrokes. When the whole mantel is covered, then brush over the surface in the direction of the grain. Carefully pop any bubbles which appear from the wet polyurethane using a pin. Permit the finish to dry for 24 hours.
Repeat the previous step two additional times so that your mantel is protected by three layers of polyurethane varnish.