Finish pulling away at crazing

[Dave Hulse]

I recently purchased a 27 year old mandolin that I knew had some finish crazing. I was playing outside yesterday with the sun shining on the mandolin and I noticed that the finish was pulling away from the top a bit at some of the finish cracks. After another 15 minutes or so I looked again and the finish damage had grown.

So I'm wondering about others experience with this phenomenon. Is it something that will continue? Just in the sunlight? Can some finish be injected into the cracks to limit the damage? Complete top refinish?

Thanks for the input, Dave

[Richard500]

I’d guess its a recent bad refinishing job with no adhesion of the topcoat because of bad surface prep or wrong material. Can’t imagine that a short UV exposure at 5000’ would damage a proper finish. Or that trying to seal the crazing would do any good. Bad prep is usually lack of sanding to create ‘tooth’, presence of waxes or silicones.
If the developing look is bothersome, the cure is a refinish, as all that peeling stuff has to be removed, probably mechanically. On a particularly valuable instrument, any refinish reduces its sales value; on a less costly one, it can be too expensive. Plus, there are few people who are confident fixing unknown finishes with any assurance of success.
Just my guess, based on the photo.

[MikeEdgerton]

People pay a fortune for distressed finishes on mandolins. Any finish can be repaired depending on how much you want to spend. I agree and seriously doubt the sunlight itself is affecting the finish. I have a friend that distresses instruments as part of what he builds and he is known for leaving solid guitar bodies on the dashboard of his car in the heat of the day then putting them in a freezer to cause them to craze. I don't doubt there's a problem with the finish itself but I think the issue is more of heating and cooling the surface.

[Marty Jacobson]

Yeesh, that's super frustrating.
Definitely a problem with the finish (or method of application). Something like a sudden change in temperature due to sitting in the sun could cause it to happen suddenly, but if it's doing this, it was always going to do it eventually. Try not to pick at it or let anyone else mess with it, it needs to be done carefully by someone who knows what they're doing, and then refinished properly. It's a real headache of a job because we have no idea of knowing what has been on there, and since there's crazing, what could be down in the wood. I would probably remove the old finish, sand it to bare wood, seal it with shellac, sand it again, and then dye and refinish. Not a very fun job. Under no circumstances try applying anything to it, it will only make matters worse and depending on the product, could make it nearly impossible to resolve.

[rcc56]

That is a condition that the late Jim Grainger called "loose finish." It is somewhat common on Martin guitars made somewhere around 20 - 25 years ago.

I have not heard whether there was any agreement on the exact cause-- it could have been due to several things, such as mis-formulated nitrocellulose lacquer or sealer, or a very large bad batch of lacquer, sealers and top coats that are incompatible with each other, or a failure to thoroughly clean and degrease the wood surfaces [especially necessary, but not limited to Indian rosewood] before beginning the finishing process, poor humidity conditions, water in the air line, etc. etc. Often, it seems to start where a finish has been subject to some sort of stress, such as a repair, or a ding, shrinking binding [especially common on Martins from the same period],or pressure of some sort.

At any rate, a complete refinish [with very thorough cleaning] is probably the most reliable solution. However, assuming the finish to be nitrocellulose lacquer, it may be possible to remove the large loose areas of finish, then brush the edges of the adjoining "secure" finish with lacquer retarder, build new lacquer where the loose finish was, wait at least two weeks, level everything, and finally over-spray the whole plate. A lot of work. The risk is that the remaining sections of original finish may develop new loose spots later.

[Dale Ludewig]

What's the finish look like on the rest of the instrument?

[Richard500]

The value of knowledge: My area of expertise is in thin films, mostly of the semiconductor device kind, and mostly things like sputtering, vacuum evaporation, plasmas. So I visited a potential customer having adhesion problems on some simpler stuff. Made a 20 page slide show (on transparencies!) on the general subject, at least relating to their product type. Gave a talk to their engineers. No questions, nothing.
But at the end, one asked if he could have a copy of the talk. I said sure, and watched this bozo tear off the front page, with my name and company on it, throw it on the floor and go off to copy the rest of it.

[Dave Hulse]

What's the finish look like on the rest of the instrument?

The finish on the lower portion of the top and the back is in good shape. On the sides and neck there are some small places where the finish is separating at the binding/wood interface. It does have a afterbuild speed neck.

I do believe this mandolin has had quite a few owners. I've seen posts that it was made in Georgia and has lived in Pennsylvania, California, New York and now Colorado so it may not have been treated with tlc over its lifetime.

For me the concern was that there was the quick change in adherence at the 3 places on the top that appeared to begin from the UV in the sunlight. I bought this as a player so am not concerned about playwear but the finish spalling off is not what I expected.

Dave

[EdHanrahan]

Just my own experience but ...

Direct sunlight makes even minor finish checking LOOK worse than it is. After an initial moment of shock 20 years ago (now 50 y/o Martin), I've learned to just not go looking for it. Others have never noticed (to the point of commenting) but they've rarely, maybe never, played it in -direct- sunlight.