finish cracks

Jack

Hi all,

I wonder what people can say about the seriousness of finish cracks? I recently noticed that my guitar developed quite a few, of pretty serious length, over the course of a week. They all run longitudinally, with some originating near the tailpiece, and others near the neck. The cracks aren't anything I can feel, but seem to be within the finish itself.

The only thing I've done differently with my guitar (it's a D'A Minor Swing if that matters) since buying it a few years ago is changing string gauge. My mother bought some .11s for Christmas, and I replaced my .10s with a set...

Any comments?

thanks,
Jack.

Charlie Ayers

Hi Jack:

More knowledgable individuals are sure to weigh in, but such cracks are most often due to exposure to a big change in humidity and/or temperature, if I'm correct. As long as they're not down in to the wood, I think it's only cosmetic, but also may serve as a warning sign to avoid such exposures.

Charlie

Jack

Hi Charlie,

That's the feeling I've had, too...we had a spell here last week where it was about 70 degrees for a couple of days, and damp, before suddenly snapping down to below freezing with over a foot of snow. Not only my guitar, but all sorts of stuff is out of whack around my apartment. We'll see...

best,
Jack.

nwilkins

I hope you're using a room humidifier Jack?

Bob Holo

Hi Jack,

Finish checking is a different problem than wood cracks though both are problematic this time of year. As NWilkins has alluded - it's important to make sure there is some humidity in the air this time of year. If the humidity is too low it can lead to cracks in the wood and those can be very serious if not addressed.

Regarding the finish checking - it most commonly happens when a guitar is exposed to cold air very quickly. Heat expands and cold contracts. The finish is thin and the soundboard is thick (relatively speaking) and there isn't much of a thermal bond between the two, so the finish gets cold much more quickly than the wood... so it shrinks relative to the wood... and cracks. There are some vinyl-laced sealer coates now (Behlen makes a good one) that go under lacquer and help fight this by bonding to the lacquer and maintaining some elasticity over a greater range of temperatures and changes - but still - quick cold is always risky. If you had your guitar indoor in a toasty warm house and you just picked it up and walked outside with it during the winter in a cold climate - you would see the cracks climb across the face of the guitar like spiders. If the cracks bother you, repair people have access to a product that softens lacquer and can reduce or repair these cracks. The stuff is called Cellosolve. http://www.frets.com/FRETSPages/Luthier ... ator1.html
but there is no real acoustic or structural benefit to fixing finish checking and unless your repair person is a good finisher he could wind up botching your finish with the Cellosolve. They are just breaks in the finish and so they make the instrument a little more sensitive to the elements but not much. The more likely detriment to having checked finish is it you get dirt in the cracks and it looks bad etc... but the cracks in the finish aren't going to travel down to the wood and start corresponding cracks in the wood. The checking will stop at the surface of the wood.

Jack

Thanks guys...I've got my humidifier going pretty much full blast all winter (wood stove); I think it was the big temperature swing that did it. Cosmetically speaking, I don't really mind the cracks, I just didn't want it to be a harbinger of structural problems.

Thanks again!
Jack.