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Hey all,

Wanted to share some tips for those who use or want to use oil varnishes.

Rosewoods are notorious for leaving tacky/sticky varnish. There's something that causes the varnish to not set up right.

If you are going to varnish rosewoods.... Tips
1. Rub on the first coat. Don't brush. Wipe it on, rub it in good, and then use a dry cloth to rub off all the excess varnish. You want the cloth to be dry when you finish with no varnish residue.

2. If it's tacky - give it plenty of UV. Direct sunlight is your cheapest and easiest source. Find a bright sunny window or hang it up outside in the sun... Leave it be till it cures. Violin guys make UV booths because they use old fashioned varnish recipes that can take forever to cure.... If worst comes to worst - look at supplemental UV light.

3. Do not recoat of it's still tacky. Keep giving it more UV. Recoating while it's tacky will just make things worse - and you risk having your finish peel or delaminate. I have heard that this can take a while. If it's still tacky after a week - consider supplemental UV or scraping it off to bare wood and using a dewaxed shellac seal coat.

4. Scuff the first coat with something gentle like scotch brite... Go very gently. Watch out for sandpaper - as you can burn right through.

5. If you just can't get it to cooperate and it's still sticky after a couple weeks in the sun - scrape it off with a card scraper and wipe on a shellac seal coat. Be sure to wipe down the shellac very well to remove residual wax/oil before you varnish.

Varnish over Epoxy. Epoxy will take varnish well but it has to be wiped down with Naptha or denatured alcohol to remove residual uncured resin. Same rules apply... Wipe - don't brush the first coat. Let it cure fully and don't recoat if it's tacky. Use UV (sunlight) to your advantage.

Generally - the next coat can be applied thicker per your usual application method and will cure just fine assuming you didn't sand through anywhere. Once again... UV aka sunlight is your friend.

Thanks

I've found that a quick coat or two of wax-free shellac will do the trick as well.

_________________
George :-)

yeah... this is bringing back horrific memories of my first. Ziricote.

Sometimes us beginners need handholding, so for those that don't know...
DO NOT, EVER, think that warming up the guitar will help.
Be completely anal about your humidity.
Zinsser shellac is your friend.

After 2- 4 months of playing around and causing multiple cracks in my back, stripping at least 5 times, someone recommended the shellac thing and it worked like a charm.

A hard lesson to learn but not soon to be forgotten...

I've just been struggling with this on a pair of guitars with Morado trim. The varnish (Murdoch's Ure-Alkyd 500) set up fine on most of it, but persisted in being tacky on the binding. Since it was all from the same board, either the heat of bending the bindings or the Super Soft 2 treatment mobilized the non-drying oil in the wood to cause the problem. Wiping down with solvent to remove the oil didn't help, nor did sealing it with shellac. In the end I had to use CA, and even that took some build up to prevent the oils from leaching through. UV helps a lot. The new LED-UV bulbs are lots brighter than the old CFLs I've been using: you'll want to make up a drying cabinet to help protect your eyes.

Yikes! That sounds like some seriously awful stuff if even Shellac didn't work it's magic.

Did the UV work or did you just have to scrape it all off and do over?

One thing I might test out... A little humidity. Many urethanes need water to cure. Normally most wood has plenty - but sometimes it needs a little more. And it can be pretty dry this time of year with the heat and all....

I also used to use a hair dryer to warm up tacky urethane and epoxy to get it to finish curing out... Before I knew better... But it worked.

I've had bindings take longer to dry as well. I hadn't used Super Soft on them, so that wasn't a factor in my case. Sealing with shellac hasn't failed me since. It's good to know of alternative approaches.

_________________
George :-)

I was finally able to get the finish to harden on the morado binding. I scraped off the tacky varnish, sanded the wood smooth, wiped it down with acetone to remove as much oil as I could, applied a few coats of CA, smoothing between and after, and then put on two or three more coats of varnish, using UV lights to cure it fast. I'm now in the process of rubbing it back. Since the whole varnish process was spread out over a couple of months, I'm getting some witness lines, but not too bad, and I expect they'll polish out. Now I know what to do next time.

Do you mind sharing a recommendation for UV lamps? I like varnish - but I want to have some UV availablr in my back pocket (besides a day on the roof of the car) in case it goes a little sideways again.

I've been using UV-CFLs. The last time I went looking for them they had been replaced by UV-LEDs. The LEDs are MUCH brighter, and work as you'd expect given the output.

An article I read some time ago stated that the varnish drying benefit of UV is linked to ozone formation. Ozone is a more reactive form of oxygen, and since traditional varnishes harden by oxidation and polymerization, that makes sense. Any type of UV will do it, and, as in smog, some VOC seems to help. The fresher the varnish coat the better the UV seems to work.

Good to know as I am about to use an oil varnish on a mahogany guitar with rosewood bindings.

Do the uv lights need to be a certain distance from the guitar? I had 4 CFl lamps set in a circle (I suppose that makes it a square... ) about 1+ foot from the guitar. It was hung in an empty closet with the doors open... for a couple of weeks.
and... (ultimate newbie dumb act)... a dehumidifier.

I didn't think the UV had any effect.
Wiping with acetone had no effect either.
Someone in an earlier thread warned that wiping with acetone can restart the oil migration to the surface. (of course I read that AFTER I wiped with Acetone )

Standard CFL's don't put out much UV... Try hanging it in a bright sunny window. A sunny window is about 100x brighter than several CFL's..

But the biggest thing is to wipe on the first coat lightly and then wipe off till there's no residue on the cloth.... Then let it cure/dry till it's all the way dry. The first coat has to be thin thin thin so it will cure... It seems like once you can get the first coat on and cured - you are more or less home free.

Trying to fix up a thick, gooey finish after the fact is a recipe for failure.

CFLs are a lot brighter than a sunny window at night. Just saying.

The UV-LED that I got is seriously bright. They seem to have discontinued the CFLs.

As John says, a really thin first coat is a big help; it can cure through fast, before the oils have time to do their dirty work. Once the first coat has set up you should be fine so long as you don't sand through to the wood.

Which ones are you using?

I have several of the UV-CFLs, but only one package left. That one is from Feit Electric; 13W, model BPESL 15T. The numbers on the other bulbs are too small to read easily. As I say, I could not find these any more, so they may be discontinued.

The UV-LED is also a Feit product: BPA19/BLB/LED. I'll say that a search on their web site failed to turn up this model. The first one I got stopped working after about a month, and the store gave me a replacement, no questions asked. The bulb gets quite hot, and the models they show now have cooling fins on the base, which may be related. One of my friends runs a lighting company, and has counseled that, when buying LED lights it's a good idea to go with domestic ones if possible; the Chinese units tend to have short service lives in his experience. In this case that's what they had, so...

I'll note that an article I saw year ago in a violin publication on use of UV to harden varnish said that it worked by creating ozone, which is more reactive than normal oxygen. As in smog, the UV reacts with VOCs. Apparently you don't need any specific wavelength for this, so any UV light will do.