Tung Oil Will Not Dry

[John Towns]

It has been 2 weeks now, since I wiped a coat of tung oil (Woodcraft) on a pair of cherry vanity doors I made. I may have made a mistake of leaving them out in my unheated garage, I mean workshop, for the first 4 days, then I brought them in. I continued to wipe them down of excess oil. When I got home tonight after being away for 3 days, the doors are still not dry.

My guess is that they either need more time to dry, or they will never dry. Since I need to finish this project up very soon, I think I will need to strip them and try again, with lacquer or shellac.

Before I do that, would it be ok to put a thin coat of unwaxed shellac over the tung oil, or am I asking for trouble?

John

[Jim Becker]

If it were BLO, you'd get a hearty "go ahead" with the shellac sealing. But unfortunately uncured Tung Oil can be a bummer if you finish over it. So I'm afraid you'll want to remove it before you attempt any other finish at this point.

My recommendation for the future is to not use Tung Oil (assuming you mean the real McCoy, not "tung oil finish" which is typically a varnish and contains no tung oil--marketing) when it's not "the" finish. BLO looks identical, cures faster and can even be over coated with shellac the same day if necessary. (I do that all the time after reading an article by Jeff Jewitt that used a similar technique) Also, oil based finishes, whether "pure oil" or a varnish, are very sensitive to temperature. (so are water bornes) Shellac, being an evaporative finish, is less sensitive, although very cold isn't condusive to a fun finishing experience.

[John Towns]

A followup question, if I may. Would the 1/3 tung oil, 1/3 BLO, 1/3 varnish blend be an option at this point, since the tung oil on the doors has not yet cured?

[Scott Holmes]

Depends... true 100% pure tung oil needs about 2 weeks to cure... why do they sell this stuff as a finish?

Adding varnish and MS to it may give you a very soft, in-the-wood finish. It may not, the tung oil may have "missed" it chance to dry by the cold exposure to the oxygen it needs to cure.

I'd be safe and remove the tung oil.

Ditto on what was said about BLO...

I have a sample I show to my finishing students; no one has ever been able to tell the difference from the BLO treated 1/2 to the tung oil treated 1/2 of the striped mahogany sample board.

[Faust M. Ruggiero]

Be patient. The tung oil will dry and will look good. If you want to leave it as the final finish and not chance top coating with a solvent based product, merely use lemon oil on a rag to brighten the finish once or twice a year. I built a huge stereo cabinet many years ago and finished it with one coat of pure tung oil. It gets a light coat of lemon oil once a year since. It's the most natural finish I've used.
Whatever you do, don't top coat it unless it is really dry. That may take weeks.
fmr