I need help! Can wood that has been oiled receive a coat of polyurethane afterwards? I accidentally spilled some citronella oil (the mosquitoes were driving me mad!) on a beautiful piece of mesquite which is already sanded and ready for stain/polyurethane. (It will be used in an outdoor covered patio area.) Is it ruined? – Kortnee
Chris Marshall: Your mesquite isn’t ruined, it’s just oily. I would first wipe the wood down liberally with mineral spirits or denatured alcohol, which will act like a solvent for the citronella oil and help to suspend it again. Then, use paper towels to blot the solvent and oil off the wood. If the oil spill is still evident after that, sand the mesquite again to remove as much of the residual oil as possible — the citronella probably didn’t actually penetrate very deeply if you wiped it off soon or immediately after the spill happened. Then, for all practical purposes, you should be back to bare wood — or nearly so — again. I’d use an oil-based stain and oil-based poly (as opposed to waterbased versions), just as one last measure of compatibility in case any citronella oil is still present in the wood. Oil and water, as we all know, don’t mix well.
Tim Inman: All is not lost. You’ve just made a little more work for yourself. Polyurethane finishes suffer, as a class, from poor adhesion characteristics. They don’t stick on the best. So, it is even more critical with them to have a clean, dry, well-prepped surface before applying coats of finish. Oils will interfere with the bonding ability of the finish. That said, to correct your problem, do what you can to remove the oil from the surface. There are any number of ways. For small spots, something like Fuller’s earth might do. But for larger areas, probably the best advice would be to use a solvent that will blend with the oil and allow you to pick it up in absorbent material, like a cloth or some sawdust. One very excellent and available solvent for this would be simple mineral spirits. It is cheap and not too highly flammable. It will dissolve with the oil, dilute it, and then let you wipe off the excess in waste rags or sawdust. Repeat two or three times. Let the surface dry completely overnight or maybe several days, then go after it!