Tung Oil finish repair

[Lordpax]

I have a cherry cradle I’m finishing using 100% Tung Oil.  The first coat was cut 50% with mineral spirits and liberally applied with a foam brush, and re-applied to cover all the soaked in areas after 30 minutes.  30 minutes later all excess was removed with a cloth.  

I then noticed on one panel what appeared to be a streak in the wood, it almost looked like a bead of sweat or perhaps a bird overhead, it was approximately 1/4x6” long.  I thought I could just sand this down, and re-apply the thinned oil.  I sanded with the grain at 320 (the final sand grit as well), in an area covering the streak, about 2x6” and re-applied the cut oil.  However, this section where I sanded, clearly stands out now - very much lighter than the rest of the panel.  I’ve tried four additional coats of tung to no avail, this area looks much lighter and duller than the rest of the panel.

The good news is the streak is mostly gone, at least it’s not noticeable for the most part.

I was wondering if anyone has had a similar experience with fixing minor defects during a Tung Oil application and if you found a similar situation and fixed it?  I do plan on continuing coats of wet sanding Tung Oil.

Thanks in advance.

 

[drzaius]

Cherry darkens as it's exposed to light. My guess is that the sanding just remove enough of the wood surface to lighten it a bit. Given time, it should even out. You could try putting it out in the sun for a few hours.

[Lordpax]

Thanks for the reply. I do understand the photochromic properties of cherry. I don’t believe I removed much material as when I sanded this area, it was with 320 and with not dry Tung Oil, it’s a pretty gummy operation.
The entire panel has been in the sunlight for a few days (at least the few rays we’ve gotten), but maybe I’ll cut a mask that only allows light on the affected area. Usually a panel will even out within a day. I’ve had cases where I sand outdoors and the panels can overlap causing visible light/dark lines. In my experience, finish sanding with 220 or 320 doesn’t remove enough material to affect the light/dark lines.
What’s odd is if I put a thin coat of Tung Oil over this area, when it’s wet, the area perfectly matches the rest of the panel with both color and sheen. After a few hours, it’s back to being lighter and duller.
I know I’m musing, but, I’m wondering if I inadvertently sealed all the pores in this area with the initial attempt to sand out the streak. That would explain the oil not penetrating, but leaves me in a quandary as to the best course of action. I should probably try to set aside the OCD and consider this “finish character”.
Cheers!

[Lordpax]

Just a follow up note to conclude this topic. Additional sunlight on the affected area for a couple of days did not darken it. What I discovered when I was wet sanding the second application was this area had an excessive buildup of Tung Oil. I’ve no idea why given it was similar grain and orientation, but, I ended up sanding a larger area and feathering the appearance so it now is blended to match.
Oh, and, just a footnote regarding this article from Mr. Flexner:
https://www.popularwoodworking.com/article/rub_to_create_a_great_finish

Sure, wet sanding produces a smooth finish, but, I believe Mr. Flexner has a bit of a mean streak in him. Admittedly it was 45 degrees or so and I started with uncut Tung Oil, but wet sanding that is like pulling taffy. I reduced the oil 25% and it was a bit easier to sand but not much. Suffice to say it was a two Advil night!
Cheers


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