Before film finishes like polyurethane varnish were widely available, paste wax was the best option for giving wood furniture and floors a protective coating, but now, the main purpose of wax is simply to polish the existing finish. You don't need much wax for that -- in fact, the less, the better; you can definitely overdo it. As far as maintaining the shine, apply new wax infrequently -- every six months or so rather than every time you clean.
Waxing Polyurethane Floor Finishes
Flooring professionals generally don't recommend applying paste wax to a polyurethane floor finish. Oiled wood floors are another matter -- they require the protection of a surface coating, which helps lock out moisture and give the wood a sheen. Polyurethane doesn't need the extra protection, and applying wax may make the floor dangerously slippery. Moreover, you'll probably have to strip the wax periodically because it tends to turn dull and yellow over time, and the wax will definitely have to come off before you sand and refinish. Stripping wax is a tedious, time-consuming process.
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But I Like Waxed Floors
If a waxed floor speaks to you of rich luster, be sure to use a paste wax intended for floors, not furniture. Floor wax is softer than furniture wax, and it's identified as floor wax on the label. In some cases, applying a coat of paste wax is the best way to hide scratches and worn spots on your floor, and it may extend the life of your somewhat worn polyurethane finish.
Clean all dust off the surface you're about to wax. In some cases, that may mean wiping the surface down with a damp cloth, but usually, a dry cloth will do. If the surface is stained, wipe it down with oil soap.
Apply the wax with 0000 steel wool or a cloth -- using a cloth may require a bit more effort on your part. Rub it on the surface, using a circular motion until the film disappears. A light coat is all you need -- if you can see ridges in the wax, you're applying too much. You can spread the wax in any direction -- it doesn't have to be parallel to the wood grain.
Let the wax dry. If you're using Minwax or a similar product, the recommended drying time is 10 to 15 minutes.
Buff the wax on furniture using a terry cloth towel, a piece of cheesecloth, a cotton diaper or an electric buffer. Use a floor buffer with a lambswool buffing pad to buff floors.
Wait from four to eight hours, then apply another light coat and buff it up, if you're not happy with the shine. Repeat as many times as you like. It's better to apply several light coats and polish the surface progressively than it is to apply one heavy one.