Coating Over Tung Oil

Once they're dry, tung oil finishes can be recoated with lacquer. November 12, 2006

Question
I built a custom one-off table several months ago and finished it with pure tung oil. Last week I sold the piece to a client and also sold the idea of making a big entertainment center to match. They want a UV protective finish on the EC because it is near windows and want me to put the same finish on the custom table I made. Can I go right over the tung oil (put 2 coats on a few months ago), or do I need to sand it and start over? I'm not sure if the tung oil actually cures, because there is no dryer in it.

Forum Responses
(Finishing Forum)
From contributor V:
It all depends on the tung oil you used. Most "tung oil" today is actually a tung oil finish. Either way, I have used tung oil in pure form and in finish form and then applied a finish over it with no problems, as long as the pure tung oil sat a week. It does matter what kind of finish you try to put over it. I have done it with precat lacquer with no problems, as long as I mist coat on the sealer. You can also use shellac – dewaxed, like Zinssner. Poly will work fine, but as we all know, that's not a production finish and a royal pain.


From contributor J:
I sprayed pre-cat on an oiled cherry jewelry box with no headaches. The oil had been dry for less than a week. As with any finish over finish, test a small area first.

From contributor D:
Tung oil finish needs to cure at least 36 hours before topcoating. After that, you should be fine as long as the tung is a tung oil finish (common tung oil and varnish blend) and not pure tung. Pure tung will take a lot longer to harden, probably at least a week or two until it could be topcoated. Again, samples are recommended. In the case of the table, you should be good to go with a topcoat.

And by the way, why can't polyurethane be a production finish? Urethanes are used all the time in the auto industry...



From contributor V:
What I was referring to was the Minwax type of poly. I know about the others and they are fine.

As to pure tung oil, I have used a brand several times that will be okay overnight. It's kind of like the old "boiled" in boiled linseed oil. Thought when I read that it would dry in a couple of hours, they were crazy, but it did, and yes, it was pure tung oil.


From the original questioner:
Thanks. The piece was made last September, so I suspect it has been long enough, and that I can simply lightly sand and then finish.