Things You'll Need
Pressure washer
Wide-angle tip
Rags
Tack cloths
Professional painter's tape
Canvas drop cloths
Water-based polyurethane
Wooden stir stick
2- to 3-inch polyester paintbrush
A polyurethane finish can prolong the life of paint and prevent ultra violet rays from causing it to fade. Unfortunately, when many do-it-yourselfers apply polyurethane over a water-based latex or acrylic paint, they end up with rampant flaking. If you want to avoid a similar outcome, choose a specific type of polyurethane, specifically formulated to bond with water-based finishes. Remove oils and foreign particles from the painted finish, before you apply the sealer, or the finish may fail.
Step 1
Wash exterior painted finishes, using a pressure washer. Intense water pressure may strip the paint. Avoid this by using a low-pressure, wide-angle spray tip. Rinse interior painted finishes, using wet rags. Let the painted surface dry for four hours.
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Step 2
Wipe down the painted finish, using tack cloths.
Step 3
Cover surfaces adjacent to the painted finish, using a low-tack tape. Spread drop cloths out beneath the finished surface.
Step 4
Open the can of polyurethane, then stir the clear finish, using a wooden stirring stick.
Step 5
Apply the polyurethane to the painted finish, using a 2- to 3-inch polyester paintbrush. Brush left to right, applying gentle pressure as you move your paintbrush.
Step 6
Look closely at the polyurethane finish to see if it is sagging. Quickly smooth these types of flaws before they have a chance to fully dry. Let the polyurethane dry for two hours.
Warning
Oil-based polyurethane will not bond to water-based paint. Be sure to select a compatible water-based polyurethane finish, or flaking will result.
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