Things You'll Need
When it comes to finishing furniture or hardwood floors, polyurethane is the key to protecting and preserving the stain. Applying polyurethane in even coats is a crucial, though not always simple task. Typically, two to three coats are used with sanding in between coats to even them out. However, do not worry if you have applied polyurethane coats unevenly. The problem is easily fixed.
Sand the uneven finish using fine-grit sandpaper. Try not to sand too hard or you may go through into the stain, requiring that you re-stain the area.
Wipe away dust and debris with a clean cloth. Make sure the area is completely clean before applying polyurethane so you do not trap anything between the coats.
Apply a very light coat of polyurethane to the sanded area with a brush. Allow it to dry and then check the evenness of the coat. If the coat remains too thick, re-sand the area and reapply polyurethane. If the coat is too thin, repeat this step until you have an even coat.