How to Apply Polyurethane Seal on Wood Furniture

Move the furniture to an open, well-ventilated work space or outdoors. If this is not possible, open all of the windows in the room and place a drop cloth under the furniture to protect the floor from spills.

Stir the polyurethane slowly with a paint stirrer. Avoid whipping the polyurethane or jostling the can, as these methods can create bubbles, which will become trapped in the finish as the polyurethane hardens.

Pour a small amount of polyurethane directly onto one of the horizontal surfaces on the piece of furniture. Spread the polyurethane over the surface of the wood in a thin, even coat. Use slow, full strokes with a foam or lamb's wool applicator, and always move the applicator with the grain of the wood.

Allow the polyurethane to cure and harden. This may take up to 10 hours, though drying times vary by product -- read all manufacturer's instructions carefully. Buff the hardened polyurethane with a piece of super fine-grade sandpaper, around 400-grit or higher.

Wipe down the piece of furniture with a damp cloth to remove any dust you created when sanding the polyurethane. Apply between two and four more coats of polyurethane, buffing each coat except for the last two.