Polyurethane is a modern substitute for traditional glazes such as lacquer. Polyurethane applied to a ceiling will give the ceiling a glossy appearance, as well as protect it from damage. If you install polyurethane with a brush or a roller, you risk leaving lines in the ceiling due to the overlapping edges left by the brush or roller. You can rent a paint sprayer from most home improvement centers and apply a coat of polyurethane quickly and evenly, with no risk of streaks.
Things You'll Need
Cover the floor and all furniture with drop cloths. Spraying polyurethane will create overspray, which will naturally fall to the ground. Anything not covered will get a thin coat of polyurethane on it.
Place two lines of painter's tape around the top of the wall where the wall meets the ceiling. Use 3-inch painter's tape, and place two strips of tape next to each other on all the walls in the room. This will prevent getting polyurethane on the wall.
Place a box fan in a window. Turn it around backward to pull overspray and fumes out of the room. If you do not have a window, place the box fan in a doorway. If possible, open a second window, simply for ventilation of fresh air.
Follow the guidelines on the technical data sheet supplied with your can of polyurethane or supplied on the manufacturer's website for the specific spray nozzle size and sprayer pressure settings. These will differ, depending on the type and brand of polyurethane you choose to use.
Open the container of polyurethane and place the pickup tube from the paint sprayer in the can.
Spray onto a piece of drop cloth to make sure the polyurethane sprays a consistent layer and does not spit out the material in lumps. If you do not get a consistent spray, increase the pressure slightly.
Spray a consistent stroke of polyurethane across the entire length of the ceiling. Hold the wand perpendicular to the ceiling and approximately 12 inches away. Overlap each stroke by 50 percent to avoid thin areas and to provide a consistent, streak-free finish.
Wear protective clothing, safety goggles and a face mask when spraying polyurethane.