Expert: Greg Scholl - 6/11/2009

Question
QUESTION: I have 25 year old kitchen cabinets.  They probably have polyurethane varnish on them.  Some of the finish is worn and showing water spots. I want to clean up and spruce up the cabinets without a full refinishing. Question:  If I lightly sand the polyurethane, what product can I use other then varnish to add some protection over bare wood and mostly old varnish.? Can I use tong oil?

ANSWER: Hi Libby, most likely your cabinets are not polyurethane, but lacquer. Lacquer can only be recoated with lacquer.  Areas of waterspots and areas of wear and no finish can't easily be repaired without some experience with lacquer touch up techniques, and often these finishes are "toned", meaning they have color in the clear coats, which makes them doubly difficult to touch up as well.......as the finish is sprayed on almost exclusively. I would not suggest using Tung oil or Tung oil products over lacquer.Hope that helps a little, although I'm sure it's not the answer you were hoping for.............
Greg

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QUESTION: Thanks Greg.   Why do you think the finish is likely lacquer?  Is there any way to determine what it is?  What would happen if I put Tung oil over lacquer?

Answer
Lacquers (and catalyzed lacquers where just coming on the market around that time, a two part, crosslinking lacquer that's extremely durable), are the preferred type of finish for Cabinets for several reasons, and in a factory setting, quick curing is the best reason. Poly's and varnishes take 12-24 hrs. to dry per coat, lacquers 30 minutes to a few hours. Also these color toning techniques are most employed with spray lacquers as well. Another point is that lacquers chemically bond to each other from coat to coat to form a single layer of film, while Poly's and Varnishes do not.They only have a physical bond from coat to coat staying in individual layers, making them less forgiving, less repairable, and less durable. Tung oil is a "long oil" which hardens slowly like a varnish, and will likely creep or crack over a hard finish like lacquer. While a single, thin application of Tung oil likely wouldn't suffer that fate, they are not compatible as a a general rule. Conventional lacquers will soften with lacquer thinner, catalyzed will not however, and neither will Varnish or Poly's, so it can be tough to figure it out....hope that helps a little, but 25 years is a good life for a finish like this, and anything other than a proper restoration by someone qualified will likely leave you unhappy with the results....