If you want to refinish your floors, it is helpful to know what type of sealant was used previously. While paint is easy to identify, other sealants can look suspiciously like one another. Take your best guess, then use one of these techniques to confirm the sealant on your wood floor. You can also use this technique for wood furniture or cabinets.
In order to determine if your floor has been sealed with wax, try leaving a few drops of water on the floor and allowing them to dry. If the water leaves white marks on the wood floor, then wax was definitely used. The white marks you created with this test can be buffed away with very fine steel wool.
If you have mineral oil, you can try a different test. Simply apply some mineral oil to the floor and wait a few minutes. Remove the oil with a white rag: if there is a yellowish brown residue that feels almost like crayon there is wax on the floor.
Keep in mind, however, that wax is often used as a final layer on wood flooring. There could be varnish or polyurethane below the wax. The underlying coating will have to be removed as well if you plan on refinishing the floor.
Lacquer or Shellac
It is unusual to find shellac or lacquer on wood floors in modern construction, but both finishes were at one time commonly used. Therefore if you have an older home, you should definitely test for shellac or lacquer.
To begin, test for one of the two by scraping off a bit of the finish with a coin at one corner. If the scraping produces a finish that flakes off, you probably have lacquer or shellac on your floors. Unfortunately, shellac, lacquer, or a combination of the two could have been used.
To test and find out which specific finish is on your floors, you have to use the chemical used to remove the finish. Start with denatured alcohol: apply a bit to the floor and wait. If the finish dissolves, shellac was used as a sealant on your floor. To test for lacquer, apply some lacquer finish to a spot on the floor. The finish should appear rough, then smooth after the area dries slightly if the floor has been sealed with lacquer.
Testing for a combination finish requires a mix of half lacquer thinner and half denatured alcohol. If you can easily remove the finish with this concoction, there is probably a combination of the two sealants on your floor.
Varnish requires either denatured alcohol or lacquer thinner to execute a test. Apply lacquer thinner, and the varnish should crack. Denatured alcohol will dissolve the finish slightly, but not affect it as much as it would with a shellac finish.
Modern wood floors are most often sealed with polyurethane. Acetone applied to the surface of polyurethane should bead and not affect the wood. If your floor reacts in this way, it has at least one coat of polyurethane on it.