How to Repaint a Table Top With Polyurethane

Set the table up in an open, well-ventilated work space. Spread a varnish thinner over the table top and allow it to sit for the recommended amount of time. This usually takes 20 minutes or less, but can vary from product to product.

Scrape the old topcoat from the table with a putty knife. Add more thinner as necessary to remove the old finish. This process may strip some of the old stain, but it will not remove all of it. Do not be alarmed if the wood looks streaked -- this is just on the surface of the wood.

Scrub down the table with a mixture of 1 part trisodium phosphate to 4 parts water. This will help neutralize the solvents while removing any residual chemicals. Allow the table to dry.

Sand down the table top with a handheld belt sander fitted with a 100-grit sandpaper pad. Sand the table until the bare wood is exposed and all of the stain is gone. Switch to a 220-grit sandpaper pad, and sand the table until it is smooth.

Wipe down the table with a tack cloth to remove the dust from sanding. Mix your stain according to the manufacturer's instructions, then apply it to the table with a brush, roller, sprayer or rag. Once the stain is on the table, wipe it with a clean cloth until no more stain comes off on the cloth.

Apply additional coats of stain if desired, allowing the stain to dry completely between each application. Stir the polyurethane gently and thoroughly -- never shake polyurethane, as this causes bubbles, which can ruin your table's finish.

Paint the polyurethane onto the table with a foam applicator brush. Use smooth, straight, even strokes, overlapping slightly with each stroke. Allow the polyurethane to dry completely.

Sand the table top by hand with a fine-grade sandpaper, around 400-grit or higher. This will scuff the polyurethane. Wipe up any dust, then apply another coat of polyurethane. Two to three coats is typically enough for most wood surfaces, though four to five is a good number if the table will be seeing heavy use.