Things You'll Need
Separate container, such as an empty jar or coffee can
Several 2-inch foam paintbrushes
Clean, lint-free towels
Polyurethane is a versatile material made from plastics. Among its many applications is its use as a durable coating for a variety of surfaces. Polyurethane applied to a countertop will prevent stains, scratches, moisture damage and discoloration, as well as create an attractive sheen and highlight the natural beauty of a surface. Polyurethane is typically applied in three or more coats, with a light sanding between coats. Thin polyurethane with paint thinner makes it easier to apply and shortens the drying time between coats. Applying polyurethane takes patience and attention to detail, but the end result is a beautiful, durable surface.
Prepare the surface of your bar. Sand the bar top lightly to remove any dirt, oil or other contaminates and to roughen the surface for better adherence of the polyurethane. Wipe the bar with a damp towel, rinsing often, until it's free of dust. Allow it to dry completely.
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Thin the polyurethane. In a separate container, mix approximately 10 parts polyurethane to approximately 2 parts paint thinner. It's not necessary to measure the parts precisely; you can dilute polyurethane up to 50 percent. Stir well with a wooden stir stick.
Apply the first coat of polyurethane. Dip your foam brush in the polyurethane mixture and brush it on the bar top in square-foot sections. Use back and forth motions in the direction of the wood grain. Brush each section repeatedly until most air bubbles and brush strokes have disappeared. Move to the next section and repeat the process, overlapping the previous section by an inch or two.
Allow the polyurethane to dry completely. This may take up to 12 hours, depending on the temperature and humidity of your work area. Check for dryness by lightly touching the surface. The surface should not be sticky, and touching it should not leave fingerprints.
Sand the first coat. Sand lightly in the direction of the wood grain to remove any bubbles, brush strokes or specks of dust.
Clean the surface thoroughly. Use a clean, damp cloth to remove the residue from sanding. Rinse the cloth often and wipe until all dust has been removed.
Repeat Steps 3 through 6 until you have applied three coats of polyurethane. Use a new foam brush for each coat.
Apply the last coat using full-strength, undiluted polyurethane. Brush thoroughly to minimize bubbles and brush strokes. Don't sand the last coat. Allow it to dry for at least 24 hours before placing anything on the surface.
Keep a small jar of paint thinner and an old rag handy to wipe up small spills and to remove polyurethane from your skin.
Apply polyurethane in a well-lit environment to allow you to see air bubbles, brush strokes and any specks of dust that fall on the surface.
Polyurethane fumes can be dangerous. Apply polyurethane in a well-ventilated area, away from sparks or flames.