MIMF

I can't find a previous discussion with this combination.

I understand that you don't want a harder finish over a softer one, but I'm not sure where these 2 stand? I've tested seperatly on scrap and they feel pretty-close in hardness.

This guitar is my blue one that I originaly finished with Water-Based Poly-Acrylic, but after a couple of years I found the finish never got hard-enough and was only getting softer.

I stripped it down to wood, restained and and then used Tru-Oil as a clearcoat, but when I went to sand it level, I was not happy with the witness-lines. I was going to try the spray, but It's not available in California. Now I just found out that Birchwood-Casey has now also stopped selling all their liquid products to California as of January.
Right now I'm trying to spray what I have left of a bottle thinned with mineral spirits and using a PreVal to spray. It's possible I might be able to finish up the project with what I have, but I'm concerned about my options if I run out or need to touch it up down the road.

If I need to fix something years later I'd hate to strip back to bare wood to refinish with something else.

I can't do Lacquer since it gets gummy from my sweat.

Is there anything else I can use on top of it?

Shellac has the reputation of sticking well to nearly any other finish, as well as most surfaces. I doubt that fully cured oil finishes would be different.

My biggest concern is wether or not shellac would crack years down the road if it was used on top of the Tru-Oil.

I don't think it would be a problem, but I don't know for sure or have any real experience to draw from. I was just wondering the same thing the other day, so I will be following this thread.

Tru-Oil is a varnish, not an oil finish. Wiping varnish, but varnish. It dries hard, and cross links in two weeks of drying. Shellac should do fine over it.

California is going to seriously limit your choices. I would rub back the true oil to the wood surface and let it dry again if you can smell it. After that any oil-based finish should be compatible but there won't be much for sale around you. If your sweat eats lacquer it probably eats through the tru-oil even faster?
I'd try the U-40 permagloss via mail order from a place like Mudhole. It's absolutely bulletproof but the smell is pretty awful. If you want 0-voc then West Systems 105 resin and 207 hardener is hard to beat but you'll have to brush it on and sand back. Lots of work either way. Shellac sounds reasonable in comparison.

There will be a slew of new finishes coming on line later this year and some of them look very promising for instruments.

If I were starting fresh I'd go with OSMO poly-x which is less fuss, less smell and seems a lot tougher than True-oil but definitely not gloss.

Since the consensus is "It'll probably work" and I don't hear any "No, not a chance" I decided to go for it. I'll be the test-subject and find the answer. I've now sanded back as much of the Tru-Oil I could before hitting my color and now I've got a couple of coats of shellac on and will let it sit over the weekend. I'll start doing more of a French-Polish style method on Monday.

If you can get Behelan's Rockhard Tabletop Varnish, that's a good substitute for TruOil. They're both oil varnishes, and I believe the Rockhard is a little harder.

edit: Don't bother with the spray TruOil, I've tried two cans and neither one of them dried properly.

I had good luck spraying the Tru-Oil in terms of how it dried clear and smooth. My problem was finding a good thinning-ratio (3-1 to 5-1 seemed to be the window) and have concistent spray results. The PreVal just has no control for flow. Also, since it's being thinned for spraying, the dry time is even longer so I was getting more dust-nibs.

I might try the Rockhard.

What is the application process? How long does it take to set up for buffing?

Check the archives, Al Carruth has posted his finishing process for Rockhard.
It also takes two weeks to a month to be ready for final buffing.

Oh.... I didnt hear tru oil was no longer available here in kommie fornyuk...

Been a while since I've used it, but had outstanding results....

Now I'll have to drive to arizona just to buy a bottle of tru oil....

I found you can still get the bottle if you order from Amazon. They won't ship the Aerosol though

I order mine directly from Birchwood Casey. They have all types, including the spray.

I tried ordering direct. They won't ship to me.

Here's a an email response I got:

Nick,

Thank you for your inquiry.

We are very sorry for any inconvenience that this may cause but Birchwood Casey has chosen to forgo selling any of their chemical products to the State of California.

Although our products comply with the laws that are in effect, the long arm of the law headed by the California Resource Board are more then we care to dance with. There becomes a time when the risks far exceed the rewards, this is one of those cases. We stopped selling all our petroleum based products back in January. And recently have decided to stop with all of our chemical products. Our targets will still be for sale in California.

Since we stopped selling the Tru-Oil back in January, that is probably why you haven’t been able to find any in California.