Banjo-Mand finish issue

[Ginridge]

I recently was asked to restore a vintage Banjo Mandolin. It probably dates to the 20s or 30s and was made by one of the big Chicago builders (Regal, Washburn, Harmony, etc) and is a decent quality and all original. It will get the full treatment; neck re-set, metalwork buffed out, frets leveled crowned and polished etc. The one big issue I have to deal with, though is finish on the resonator back. The finish is failing and "white-ing out". Usually this can be resolved by wiping with an appropriate solvent (usually Alcohol since most instruments of this era have a shellac finish) but that does not work in this case. I have tried both alcohol and lacquer thinner, both of which remove dirt, but do not help to restore finish. The "white-ing" actually gets worse. I could simply sand through the old finish, but the back is birds eye maple that has been colored in a geometric pattern and sanding off the finish will also remove the staining pattern.

I'm hoping the collective community might have some insight into dealing with this. Thanks in advance!

[Dale Ludewig]

Have you tried hitting a tiny bit of it with a heat gun? It looks like moisture trapped in the old finish. I've had much success over many years with getting it hot enough to vaporize the moisture out. It's a little dance with the devil temperature wise. (I'm not saying this will work but it's worth a try.) Of course it's not going to help with the area where the finish seems to be gone.

[sunburst]

If it is spirit (shellac) finish of some kind, alcohol should have done it if a solvent is capable of clearing it up. You could try gentle heat, like a hair dryer from appropriate range, constantly checking to avoid overheating and resulting finish damage.

If it is lacquer, a slower solvent might help. Lacquer thinner evaporates pretty fast so it doesn't have long to work, and furthermore it can cause serious finish damage. Butyl cellosolve is often sold as "lacquer melt" or some such trade name. It evaporates much more slowly than thinner and is much less likely to harm the finish. It might work. Also, gentle heat from a hair drier as already mentioned.

edit:
Great minds, as they say...

[Ginridge]

Thanks very much, John and Dale. I'll look for the slower solvent and try a gentle heat to see if that does any good. I'd hate to have to sand it down and try to re-match the staining.

[sunburst]

...I'd hate to have to sand it down and try to re-match the staining.

So would I. In fact, I don't think i would try it unless it was absolutely necessary. Sometimes "it is what it is".

[j. condino]

All of the whiting out and finish issues are from a century of tears by everyone else who has been subjected to the sound on one of those things!

[Dale Ludewig]

James,
Have you no respect for tradition? Alas.

[pops1]

These instruments get a bad rep because folks put mandolin strings on and make them obnoxious. Using light strings like a banjo would, they are a banjo after all, makes them much more usable.

[Ginridge]

These instruments get a bad rep because folks put mandolin strings on and make them obnoxious. Using light strings like a banjo would, they are a banjo after all, makes them much more usable.

Ha! I'll put light strings on it if that will bring world (or banjo) peace!

I'll look at options but definitely believe in the 'do no harm" method of restoration. More importantly, I'll see what the client wants. I'm trading the work out for album graphics so I want to get this right for him (and me)...

Interestingly enough, I just ran down to the workroom and did about 3 minutes of heat from a hair dryer on the damaged area and and was pleased to see that it actually removed about 70% of the white-ing. I'll get into that with a bit more precision tonight.

[pops1]

Ha! I'll put light strings on it if that will bring world (or banjo) peace!.

I like nothing heavier than a 28 for the G string.

[Ginridge]

To report back, the heat method indeed does work. I used a moderate heat, watching constantly, to make sure I didn't scorch anything, then followed with a light alcohol wipe. That took care of the worst of it. If you look at the pic below, I treated the dark section on the top (near hair dryer) as described, but the the bottom section has not been treated yet.