Sticky Old Masters

[JonathanF1968]

Hi all,

I tried using Old Masters Tung Varnish on a piece of spalted maple to make a clipboard (a fine companion to a pen) and the finish is behaving strangely. The first two coats were lovely. After a few hours, they felt nice slick and smooth to the touch. Then coat 3 never quite got that same feel. If has a slightly tacky feel to it still, after letting it sit/cure for three weeks. Paper doesn't stick to it, but it doesn't feel nice. (Doesn't look nice either.) Any thoughts? I sanded to about 220, raised the grain with DNA and then sanded one last time and blew off the dust/dry paper towel. Rubbed on the finish with paper towel, let dry, light buff with 0000 steel wool between coats.

--Jonathan

 

[leehljp]

This is a personal thing with me - I stopped using Tung Oil "blends" long ago because they do not uniformly work in the manner of pure tung oil. Even "pure" tung oil comes in different "varieties": pre-catalyzed and raw, and maybe another. Blending with "varnish" and others changes some of the characteristics but generally it means that it cures faster.

One characteristic that is sometimes overlooked with tung oil is that it takes time to set up and cure. Application is to wipe on or use a paint brush to apply; then within a few minutes wipe off the excess. Thicker applications don't work on tung oil. Apply and wipe off excess - any that would run if the board were held vertical. If not, the finish might set up and take a long time to cure.

Now to your specific situation: If I were to "guess", I would have waited 24 hours between coats one and two; 24 to 48 hours between coats 2 & 3. While 1 & 2 felt fine, generally tung oil itself will set up but not cure for 24 hours and that varies with the temp. IF the underlying coats were not fully cured when coat 3 was applied, it is possible to arrive at the situation you mentioned. Setting up and curing are two quite different characteristics. I run into this with Medium and Thick CA in cool weather. Setting up and curing are quite different. Time or lack of adequate Time is the difference in a good finish.

Just guessing. Could be wrong.

 

[duncsuss]

What Hank said: it sounds like you didn't wait for each coat to cure before applying the next.

Same thing happened to me with Tried & True Danish Oil.

 

[JonathanF1968]

Thanks, I suppose that is possible. My experience with pure tung oil is that it can take a lot of coats and still feel and look nice, so I was surprised that this was behaving as it has. And also that after three weeks, it still has a relatively strong smell, like it never really totally cured.