Crack in Martin koa ukulele

Henning · #1 04-20-2019, 09:47 AM

I won an auction at ebay concerning a Martin CK1 ukulele, made in Hawaiian koa in Mexico.
The ukulele arrived but when I tuned it I reckoned there was a strong bending of the saddle. So I took it to a shop to get their point of view.
When placing the ukulele in my back pack, I happened to slip it down a few dm, simply dropping it, thereby causing a mark in the lower end of it and making the grip for the zipper to come loose.
Some few weeks later I found a crack in the back, about the length of (one) 1".
Could the crack have been caused by the "dropping" of the instrument, in its Martin carrying bag down in to my back pack?
Please notice, the crack goes above the lower waist bar. The hit was taken up by the very bottom of the instrument.
The seller claim moisturizing the instrument (to 80%) I run an air humidifier too. But the ukulele was on its way to me for about a little less then one week.
I tried to gently clean the crack (inside) it goes all through. Thereby finding a clear miscolouring of a tops in comparison to another part of the ukulele. How can this come?
Please see links for photos:
https://www.dropbox.com/s/2ft03hmjaf...01304.jpg?dl=0
https://www.dropbox.com/s/c2zp3rsmqg...01300.jpg?dl=0
https://www.dropbox.com/s/23bn5msibr...01298.jpg?dl=0

charles Tauber · #2 04-20-2019, 12:16 PM

I’m not entirely sure what you are asking. It is possible, I suppose that dropping it on its end could crack the back.

You didn’t say from where the instrument was shipped. It could be that the humidity level from the seller is much higher than yours. If so loss of moisture could be the cause of the crack.

I’m not sure with what you are “cleaning” the interior, but if it is a solvent it can leech color from the surface of the wood.

Earl49 · #3 04-20-2019, 05:45 PM

Quote:

Originally Posted by Henning

....The seller claim moisturizing the instrument (to 80%). I run an air humidifier too. But the ukulele was on its way to me for about a little less then one week.

Humidifying to 80% RH is a very high number, tropical conditions like for Hawaii or Indonesia. Although suspiciously high, if that is the humidity that the instrument is really accustomed to seeing, then anything markedly lower would be "dry" by comparison. Martin built it at 45-50% indoor RH. It is possible - maybe likely - that this is simply a dryness-induced crack. Are the fret ends sharp or protruding? Is the top sinking below flat across the bridge and lower bout? These are usually the first visible symptoms of a dried instrument.

Being in Sweden, you won't see indoor RH anywhere near that number, except maybe in a wet sauna or maybe a greenhouse. Have you measured the indoor RH in your house? When I lived in Alaska, we had to struggle to get indoor RH values above 15-20% during the heating months.

Henning · #4 04-22-2019, 04:36 AM

I simply moisturized a tops lightly with water then drove it along the crack. According to what I´ve read (I believe in The guitar book by Tom Wheeler, that) Martin builds there instrument in a RH of 35 to 45% at 72 to 77 F, which would equal 22,2 to 25C.
The instrument was shipped from Portugal, but as it was stored in a climate controlled environment that should be of less importance.
I run an air humidifier here that is set on 40% which means that humidity in winter will generally be a little lower than that.
The air humidifier has a hygrometer as well as the fact that I have a wall hanging hair hygrometer and a cheap Chinese electronic device too.
With the risk of nagging, what might have caused the miscolouring of the tops in the vicinity of the crack?
Or would you say that the miscolouration of the tops in the vicinity of the crack isn´t in any way related to the crack?
No, the frets were smooth on the neck. But, the top was/is dropping in to the body between the saddle and the soundhole.

Earl49 · #5 04-22-2019, 02:32 PM

I'm not an expert like others here, but when flooding an area to see if a crack goes all the way through, most people use naptha on the outside and look for wetness on the under side of the top. Naptha won't harm nitrocellulose lacquer and evaporates cleanly. Using water has the potential for staining the wood or wicking under the finish to cause clouding.

A sagging top generally indicates a dry top. Try to get the humidity up higher for a couple of weeks and see if it returns to flat and the crack closes up tightly.