As polyurethane finishes grow older, they have the tendency to give off a yellow hue. This unappealing situation is an unfortunate side effect of chemical ageing. In order to revive wood furniture and return it to its natural beauty, you will need to remove the original polyurethane finish. A polyurethane stripper can help accomplish this; the result will be brilliant, bare wood that can be treated with a new stain or finish that will keep it looking majestic for years to come.
Wear rubber gloves and safety goggles. These two safety items are of great importance whenever you use a polyurethane stripper. The rubber gloves will protect your skin from any direct contact with the stripper (which is a caustic substance), and the goggles will protect your eyes from any unexpected splatters.
Open up the windows and let in the fresh air. Polyurethane stripper needs to be used in a well-ventilated area. Keeping your workspace free of children and pets is also suggested. The fumes can be overpowering, so it is important that you maintain good air quality by opening as many windows and doors associated with the work area as you can to allow for proper air circulation.
Apply the polyurethane stripper evenly to the surface of the wood. A paintbrush works best to apply the stripper; brush on a liberal amount with even strokes. The stripper will bring about a chemical reaction that will break the bond between the polyurethane and the wood.
Remove the polyurethane using a metal scraper. Gently run the scraper along the wood in the direction of the grain, picking up the polyurethane as you go along. Continue the process until all of the polyurethane finish is removed and you are down to the bare wood.
Sand the bare wood with a fine-grit sandpaper until it is completely smooth. Sanding the bare wood will perfect it, rendering it ready for painting or staining. It will also help remove any remaining polyurethane residue.
Protect the bare wood with your choice of sealers. A light coat of varnish, paint or stain should adhere perfectly to the sanded surface and make it look new again.
As you remove the polyurethane with the scraper, you may want to consider using a soft cloth to wipe the area as you go along. This way, you can see what you have removed and what you still need to work on.
The scraper should glide smoothly along the surface of the wood, carrying pieces of polyurethane finish with it. If this does not happen, the polyurethane stripper has not fully finished doing its job. Let it set a while longer, then give it another shot. Be careful not to scratch the wood surface with the metal scraper. Holding the flat side of the metal scraper against the wood will prevent you from making gouges and scratches.