Pores Reappearing in French Polish

[Walt]

I’m having an issue french polishing over Macassar Ebony. I have gotten it level sanded and buffed a couple of times to a glass finish, but after it sits for a couple of days, I notice the divots from the pores show back up. The pores are not super noticeable—they are hard to see in the pic because the light overexposes it, but you can see them in person from the right angle.

I don’t think I got a great initial pore fill; I’m pretty sure I didn’t thin the timbermate down enough. But I built up several layers of shellac and level sanded along the way.
Is a bad initial pore fill the culprit? Or is it normal for shellac to settle back into the pores after some time? The first time the pores reappeared it was more drastic than it is now. Maybe I should level sand and build up more shellac.

[Marty Jacobson]

Well... french polish is never a glass finish. You got a great finish, by any standard. Nothing wrong that I can see. If you want plastic, build with plastic!

[rcc56]

I tend to agree with Marty on this.
All of our best varnishes and lacquers will sink into the grain, sometimes quickly, sometimes it takes years. It's one of the things that gives character to a finish.

If you do feel you must have it "smoother," you can wait 2 weeks, level sand it very lightly, and polish over it once more. But unless it's sunk in a lot more than it appears in the photos, I would likely choose to leave it alone. Otherwise, you might just mess up a finish that looks pretty darn good to me.

One thing I've learned about French polish finishes: Time and patience are your best friends. Give it time to cure before you decide whether to do anything else. And the longer they cure, the better they look.

For the record, I've never used Timbermate or any of the other water-based fillers. When I've French polished with shellac, I've used the old-fashioned "loading" process to fill the pores, using very thin shellac and pumice.

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I just looked over my most complex and difficult French polish job, which was done about 18 months ago on a personal instrument with a varnish finish, original formula unknown. The instrument had a really bad side crack that had been poorly repaired with epoxy, and an area on the back that had suffered multiple cracks from a fall. The repairs required sanding several large areas down to bare wood. The first couple of attempts to blend everything in didn't work out; it was taking too much shellac to get the repairs level. The shellac kept clouding up and wasn't curing hard enough. Then I found the right solution for this particular instrument-- 3 coats of violin maker's oil varnish, followed by a few coats of French polished shellac. When I finally got it to a point where I wasn't too unhappy with it, the refinished areas still looked a little heavy and the lap lines were more noticeable than I would have liked. But I knew it was time to quit.

6 months later, I went over the lapped areas with very fine sandpaper, kissed those spots with a tiny bit more French polish, let it sit a month, and went over the whole thing with rottenstone and oil. Now, a year later, the refinished areas have thinned out considerably with time, and the lap lines are almost invisible. It's hard to tell that the instrument was ever repaired, which is the best we can hope for in the repair business.

That instrument was a real learning clinic for me. It's where I learned about the value of time on varnish finishes.

[Walt]

Awesome, thanks, y’all! That makes me feel much better. I was worried that I had some misstep along the way.

[rcc56]

If you ever get a chance, try and get a look at an old Larson or Martin instrument in really good condition that was built before the changeover to lacquer. To me, those are some of the most beautiful finishes I've ever seen on fretted instruments.

A few years ago, George Gruhn had a 1919 Martin 000-30 in his shop, the only one ever made. It had perhaps the most beautiful finish I've ever seen on a guitar. I wish that Martin had made a record of what they used for the varnish and how it was applied.