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  #1  
Old 01-03-2020, 05:38 PM
pick1 pick1 is offline
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Default Gibson J-29 with two top cracks - how to fix them ?

Hi all,

I purchased my Gibson J-29 about three months ago (online) and I was leveling its frets yesterday when I spotted 2 cracks on the top . I've attached pictures of both (they are next to each other) so I won't explain where they are (hope the links work).

The crack closer to the high E-string I can also see it looking inside through the sound hole and it seems to go past the bracing all the way to the neck insertion point . The other one seems to stop at the bracing (for now ...).

I ran quickly to check the pictures provided by the seller at the time of purchase and I could see the crack between G and B being there (now knowing where to look) - so the guitar came with that one. I couldn't see the other crack on the picture but those pictures were definitely taken looong before I made the purchase. So, who knows ...

Another thing that should have raised a red flag for me before putting the money down was the color of the top: very pink-orange, as if it was 30 years old, not 5 - a sign that it must have spent a significant amount of time in full sun and supposedly not enough humidity. A fact which I guess was responsible for the cracks.

So, after this long introduction, how can I fix those cracks ? Humidify the guitar for 2 months then put thin superglue (StewMac #10) over the cracks on both inside and the outside ?

Thank you !




Last edited by pick1; 01-03-2020 at 10:46 PM.
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  #2  
Old 01-03-2020, 05:50 PM
pick1 pick1 is offline
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Uh, oh, I used Shutterfly to host the pictures - which doesn't seem to work with this site (I think the links Shutterfly provide use redirection ...). Will try to upload them on the imgur later tonight.
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  #3  
Old 01-03-2020, 05:56 PM
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DenverSteve DenverSteve is offline
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I would just take it to my luthier and have them glued and cleated.
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Old 01-03-2020, 11:09 PM
pick1 pick1 is offline
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OK. Links to images are now working

Quote:
Originally Posted by DenverSteve View Post
I would just take it to my luthier and have them glued and cleated.
Hi Steve,

I don't have a luthier as so far I have never needed one. I love working on guitars (though so far I've only worked on electrics, but I worked on those plenty) and as such I've learnt to do everything myself.

So taking to a luthier would be the last option - so **last** in fact that I doubt it'll ever happen since I am too much of a DIY person.

I have tools plenty and I'm not afraid to use them

Soo ... how are these cracks fixed, if they need fixing ?

Have read in several different posts dealing with fixing acoustic tops that the initial step is humidifying the guitar. Some suggest hanging the guitar vertically and putting it inside a trash can plastic bag that has a large soaking wet sponge in it (the guitar body obviously doesn't touch the sponge). The bag is tied close at the heel and the guitar left like this unperturbed for 3-4 days.

Then ... what ?
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Old 01-04-2020, 01:03 AM
Howard Klepper Howard Klepper is offline
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There is no point to the trash bag and wet sponge thing, because there is no use in overhumidifying, and that is what you would be doing in a saturated, 100% RH environment.

The first thing to do is know what the humidty is where you keep the guitar. There are many cheap digital hygrometers. Most are about just as good as each other, so don't worry about the brand. But they can all vary from one sample to the other, so it's a good idea to get two. If they read about the same, it's more likely to be a reliable number.

If your room is below 40% humidity, that is not healthy for the guitar, and should be brought up to the ideal range of 45-50% with a humidifier. Or you can humidify it in its case. That is easier to do, but then the guitar gets exposed to a humidity change every time you play it, so I prefer to humidify (or dehumidify) the room.

You can bring the humidity up a little over ideal to close the crack, but if you have to bring the humidity over about 60% to close the crack (give it a few days to a week to close up), then it is likely to open again or crack somewhere nearby when you go back to the ideal humidity. So in that case the crack needs a cleat, which will stabilize it even though it's not tightly closed. If it closes at about 50-60%, just gluing the crack should be enough, but a cleat can't hurt after you have the crack closed.

Don't use CA glue--it can mess up the finish. The ideal glue is hot freshly mixed hide glue. But if you don't have experience with that, just use Original Titebond. You can work it into a closed crack by saturating the surface and flexing the crack slightly several times. Then wipe off the excess with a damp (not wet) rag. Wait a day before putting any stress on it.

The crack along the fretboard edge is possible trouble, because it can be caused by the fretboard shrinking, which may mean the fretboard wood was not well dried to begin with. Keep an eye on it, and keep it in humidity above 40% and ideally 45-50%.

Come back if you have problems. If you are handy and like to DIY, you can fix this yourself. Also, check Frets.com for very reliable advice on repair. I'm sure there are some things there on basic crack repair.
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Old 01-04-2020, 04:13 PM
pick1 pick1 is offline
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Thank you so much Howard for coming back to me on this and for your valuable advice !

Quote:
Originally Posted by Howard Klepper View Post
The first thing to do is know what the humidty is where you keep the guitar. There are many cheap digital hygrometers.[...]
I bought a digital hygrometer a few weeks ago (will buy a second one as suggested) and the indoors RH fluctuates between 30% and 50%, depending on the outside conditions (I am in Northern VA and it's winter at the moment). If it's rainy and not too cold outside, the indoor RH would be in the upper 40%. If the cold kicks in though, the indoor humidity drops in the low 30% as the house heating system drives most of the moisture out.

Quote:
Originally Posted by Howard Klepper View Post
If your room is below 40% humidity, that is not healthy for the guitar, and should be brought up to the ideal range of 45-50% with a humidifier. Or you can humidify it in its case.
In this neck of the woods we need dry conditions (RH ~ 30%) during winter time because the springs and summers are extremely humid (RH 100% night by night) so a dry winter gives our respiratory system time to recover and helps us fight the mold.

I know some have dedicated rooms to humidify their guitars but I cannot afford that luxury especially since having a constant RH of 50% is, at least around here, a recipe for growing mold.

Since this is my "every day" guitar, I don't intend to keep it in a case - it will sit on a stand all the time so I can grab it quickly every time I can (or happen to wonder through that room). The way I see it the guitar will have to adapt to what I can provide and to my environment (it is what it is, dry winters, humid summers). If it develops a crack because of that, I'll glue/cleat it to the best of my abilities. If at some point the guitar breaks, so be it, I'll buy another one (curing my GAS as part of the process ).

I've always wondered how others are keeping their guitars ... There should be millions of guitar owners out there - do all of them have hygrometers, which they check every day, do they have rooms dedicated to keeping instruments humidified ? What did people do 20-30 years ago ?

Quote:
Originally Posted by Howard Klepper View Post
So in that case the crack needs a cleat, which will stabilize it even though it's not tightly closed. If it closes at about 50-60%, just gluing the crack should be enough, but a cleat can't hurt after you have the crack closed.

Don't use CA glue--it can mess up the finish. The ideal glue is hot freshly mixed hide glue. But if you don't have experience with that, just use Original Titebond. You can work it into a closed crack by saturating the surface and flexing the crack slightly several times. Then wipe off the excess with a damp (not wet) rag. Wait a day before putting any stress on it.
Many thanks for all the advice above. I'll go buy cleats and soundhole clamps. Already have and used Titebond. But I've watched Dan Erlewine's video about using hide glue and it looks straightforward to me so I intend to use it. Will check the Frets.com as suggested !
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Old 01-19-2020, 12:27 PM
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Just an update on this:

I humidified the guitar thoroughly for a few days prior to gluing and cleating. As a result the cracks closed almost completely and virtually disappeared.

I purchased hide glue and a glue pot, prepared it but couldn't get any in the cracks from atop (no enough space to use the "suction cup" method, the brace was kinda close to flex the edges and the crack was basically shut). So I warmed up the area with a halogen lamp and applied hide glue from underneath => the heat and water from glue opened up the cracks and swelled the top a little So I've quickly cut two cleats and applied them then clamped everything with a small flat wood bar on top to level it and prevent swelling. Left it alone for 24 hours.




A few days later I've applied the second pair of cleats which was pretty challenging from a clamping perspective.



And here is the work completed:

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Old 01-19-2020, 12:40 PM
pick1 pick1 is offline
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Now question is, what to do with the remaining hairline crack along the fingerboard (as Howard said, must have been caused by the fretboard wood shrinking):



That portion is over the neck joint block so I cannot clamped it or flex it. Considering the consistency of the hide glue, I doubt I'll be able to get anything in the crack. So ... I was thinking that in this case to use a very, very thin layer of super glue (StewMac #10) just to seal the wood and prevent the finish from flaking. Will that work ?
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  #9  
Old 01-20-2020, 12:20 PM
Howard Klepper Howard Klepper is offline
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I would use thinned hide glue. CA has too much potential to mess up the finish. So long as the top is glued to the block it's not going to move in any case.
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