This week’s Ask The Craftsman Question comes from Johnathan.
“How can I tell what type of finish is on my wood floors?”
Johnathan, get out your chemistry set and I’ll show you how to determine the different types of wood finish. The process is fairly simple, you just have to test in a specific order because certain solvents will dissolve several finishes while others will only dissolve one type.
Make sure to do this test in an inconspicuous area since you will likely be dissolving the finish off your floor.
Test #1 Is it Wax?
Put a couple drops of mineral spirits, naphtha, or turpentine on the surface you want to test. Let it sit for a few seconds and then rub it into the area. If the finish dissolves, congratulations, you’ve got a waxed floor! If nothing happens, move on to the next test.
Test #2 Is it Shellac?
This time apply a small amount of denatured alcohol to the finish and do the same process. If the finish dissolves, this time then you can be assured you have a shellac finish. If nothing happens it’s time for the next test.
Test #3 Is it Lacquer?
Go get some lacquer thinner and apply it to the finish and see what happens. If it is lacquer, the finish will dissolve pretty quickly. If nothing happens… you guessed it, next test. Warning! If you haven’t done Test #2, lacquer thinner can also dissolve shellac and make it sticky and soft. Test with denatured alcohol before moving on this test.
Test #4 Is it Water-Based?
This time we’ll try Xylene. Let it sit for a bit longer than the others and then wipe it off. Xylene won’t completely dissolve water-based finishes, but it will soften them and make the surface sticky. If nothing happens…the you have oil-based polyurethane.
Hope this helps! Just remember that you MUST do these tests in the specific order listed otherwise you may get false positives for the wrong finish. Good luck!