Tung Oil Question

[gregbois]

Hi All:

I recently built a bench for the foot of our bed, out of red oak.  I decided to apply a tung oil finish, using Real Milk Paint Pure Tung Oil.  For the first two coats, I diluted the tung oil 50/50 with natural citrus solvent.  The top coat I applied at 100% strength tung oil.  The finish went on very easily, and I wiped it off after around 40 minutes, per the manufacturer's instructions.

The top coat, however, has either lifted the grain or is perhaps itself puckering.  Hard to say which.  The piece was sanded by hand, and I raised the grain three times during the last pass with 400 grit paper.  Still, after letting that final coat cure now for a week, the tung oil feels a bit like crocodile skin.

I have rubbed the finish with wood shavings, and this has helped to smooth it out, but the wood still does not have the silky feel it had after sanding but before the finish was applied.  

I am not sure how to get the finish to smooth out to a lustrous feel.  I am also sure there is some pilot error on my part, since I'm a novice to this type of finish.

Any advice?

Thanks,

Greg
Dry-as-Dust Los Angeles, CA

[Wildwood]

Web site direction say: For the majority of all projects, you will thin 50% with thinners for the entire finishing process.

You may need to wipe off last coat with solvent to remove blistering. Then proceed with thinned tung oil 50/50 mix. To get full protection with tung oil takes anywhere from four to eight coats depending upon wood species. Drying times can and do vary.

I had success using mineral spirits as the solvent/thinner, never used citrus!

[fredhargis]

I may be way off base, but I'd bet that citrus solvent is you problem. You could do a piece of scrap with the real stuff and see if it behaves the same way.

[gregbois]

Thanks everyone.  I think trying to wipe it off with a solvent is a good idea.  And I will try a sample piece as well.  I thought when I'd read the instructions it said first two coats, 50/50 and then full treatment thereafter.

As to the citrus solvent, the interesting thing is, when I did the 50/50 coats there was no blistering.  So, maybe that's a clue, too.

Thanks again. 

Greg

[jteneyck]

Thanks everyone.  I think trying to wipe it off with a solvent is a good idea.  And I will try a sample piece as well.  I thought when I'd read the instructions it said first two coats, 50/50 and then full treatment thereafter.

As to the citrus solvent, the interesting thing is, when I did the 50/50 coats there was no blistering.  So, maybe that's a clue, too.

Thanks again. 

Greg

The directions may very well said to thin the first two coats, but did they really say to use Citrus solvent?  Maybe, but I've never heard of that being recommended as a thinner.  Like Fred, if it wasn't specifically recommended that would be my first guess for the root of the problem.  Generally, the recommended thinner is the same solvent listed under clean up.  

Assuming your tung oil is soluble in mineral spirits, that's what I'd first try to remove the alligator skin feeling.  If that's a no go, you could move up to lacquer thinner.  If that doesn't do it, then I think it will be time for a chemical stripper and a rewind to zero.  Don't use steel wool for this or anything else when it comes to oak.  The fibers are easily snagged in the grain and have a nasty habit of rusting later and making a nice black spot.  

John

[Roly]

The directions may very well said to thin the first two coats, but did they really say to use Citrus solvent?  Maybe, but I've never heard of that being recommended as a thinner.  Like Fred, if it wasn't specifically recommended that would be my first guess for the root of the problem.  Generally, the recommended thinner is the same solvent listed under clean up.  

Assuming your tung oil is soluble in mineral spirits, that's what I'd first try to remove the alligator skin feeling.  If that's a no go, you could move up to lacquer thinner.  If that doesn't do it, then I think it will be time for a chemical stripper and a rewind to zero.  Don't use steel wool for this or anything else when it comes to oak.  The fibers are easily snagged in the grain and have a nasty habit of rusting later and making a nice black spot.  

John

The Real Milk Paint web site shows the citrus solvent as a thinner for tung oil. They even sell a 50/50 product of tung oil and citrus solvent.   The problem was applying it full strength.   (I would not have thought citrus solvent would work either )  Suggest using straight citrus solvent and see if it removes it before more drastic measures.  
 Never forget the the rule of trying on scrap rather than the project, especially with new to you products or procedures.   Roly

[Wildwood]

How to apply pure tung oil the right way or just another opinion!

https://www.youtube.com/watch?v=H2nXspdV1_c

He does address most of the solvent/thinners you can use.

These people have been recommending a citrus solvent for as long as can remember. Their products little expensive!

http://www.sutherlandwelles.com/prepproducts.html

Pure drying oils like Tung and others don't really penetrate deeply without solvent thinner.

[Alan S]

It sounds to me like a too thick coating trying to cure.  It may be that you did not wait long enough between coats, so there was still a softer layer of less cured finish below the outer surface.  Tung oil cures very slowly, and air, heat and light help the process.  I am not an expert, but have had success with pure Tung oil when I wait at least several days between coats, making sure to keep the surface warm and lit while waiting.

[gregbois]

Hello Again Everyone,

Thanks for all the insights and thoughts.  I spoke to Real Milk Paint, and then said to wipe down the last (full-strength) coat with the citrus solvent and that should cut the alligator effect.  Haven't had a chance to try, but I am hopeful.  Certainly, I do not want to have to strip off the finish altogether.

I was also told to always dilute 50/50, so that could be the source of my woes since in all other respects I applied thin coats, wiped them down thoroughly after waiting for the oil to penetrate, and let each coat cure for several days before applying the next.

Alas, I did not do as I should have done, namely, test a small scrap before blundering ahead.

Hoping to achieve a better result as I move forward.

Cheers.

Greg