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I've got a humidity crack on a top of a finished guitar. In the archives, HHG is recommended for repairig the crack followed by a cleat on the inside of the box. It's not clear to me how to get adequate coverage with the glue to both sides of the crack. Do you thin it? Thanks for the help and any suggestions.

I like my crack repair hide glue to be about the consistency of water, probably thinner than most would use for brace gluing. Another good idea (from Rick Turner) is to work some warm water into the crack before using the glue as the water will draw the glue in. Rub the glue in with your fingers and work it in well, you'll have 30 to 45 seconds to do this and I tend to use them!

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Jim Howell
Charlotte, NC

I have never repaired a crack so this is just an idea that might be interesting for some of the pro repair guys to consider and comment on.

1) Return the guitar to proper RH where the crack closes up on it's own. Using a balloon in the sound hole as a plug and inserting and sealing the business end of a compressor in the end pin hole.

2) VERY carefully increase the air pressure inside the box until the crack opens up again. This will require some good regulation on the compressor.

3) Inject HHG as Jim suggested even using Rick's method - kill the compressor and pop the balloon and the crack seals itself. Since you only have 15 seconds to get clamps in place with HHG unless you work in a hot room this would be a way to close the crack in a second or two.

4) If cleating - cleat after the crack is closed and the glue has cured.

Would this work?

Hesh's suggestion to rehydrate the guitar is very important. Excessive dryness seems to be the root of most top/bottom cracks. After working on my Stella, who's back had more cracks than Keif Richards' face , I found that getting one hand in the sound hole and using a bit of -- surprisingly little -- pressure with a finger or two would open the cracks sufficiently to work glue through the crack. You don't need to see daylight through the crack to have the glue penetrate. The really cool thing about HHG is that you can put small cleats in with 'rub joints' and you don't have to try to wiggle jack braces around inside the guitar, blind with one hand . I do use a little thicker glue for the cleats.

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Jim Howell
Charlotte, NC

That would take more guts than I've got! I have visions of a pile of splinters blown all around the room! Seems like I've heard a story like that before.

Anyway, how would you get the glue in the crack against all the air that will blowing out under pressure?

Aside from that, restoring the humidity is a given before repair. I'd probably rig up a brace jack or something of the sort to open it up a little. Or, like jhowell, test the waters by trying to open it up with finger pressure. And cleat it afterwards. I haven't used HHG for crack repairs (yet), but a thinned down mixture makes sense. On the back and sides, I've used thin CA, which worked fine and made an invisible repair, but I will definitely use HHG if (when) I need to fix a top crack.

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Wes McMillian
Santo, TX
http://www.wesmcmillian.com

I typically just rehumidify until tightly closed, reach inside to push it open, then work in some hide glue with my (very clean freshly washed) finger. If I decide to thin it much it I just brush in a bit of water from the glue pot, essentially mixing it on the face of the guitar as I'm rubbing it in. For many top crack repairs there is no need for clamping at all. The key is making sure that it will close tight and even after working in the glue. If the two sides of the crack won't reliably return to flush when you release from the inside to let them close, you need to make sure you have a strategy to bring them that way before the glue gels. Clamps or magnets along with plexiglass cauls are my typical route.

If a crack is really tight, or something like bracing prevents you from being able to open it up, I've been using my heat gun more often. I gently warm and dry the wood on the inside for a few minutes before and sometimes while I'm rubbing in the glue. The idea is not only to warm the area to extend the glue time, but also to dry and starve the wood a bit, making it more eager to wick the moisture (carrying glue with it in this case) down to the bottom of the crack.

Then if any cleats are needed you can deal with that later. If it's a fresh, clean, well joined split, you have no more need for a cleat than you would on the center seam of a bookmatched top. If it's old, dirty, twisted, splintered, or in a particular high stress area, (think pickguard cracks}, then you may certainly want to cleat, but it's not always needed. I probably cleat about half of the top cracks I repair. It's a judgement call.

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Eschew obfuscation, espouse elucidation.

Yeah....... good point...... Somebody slap me for that one.

David--

Thanks for the tip on thinning the glue at the time of application. this will save me some grief in the future. I've been making HHG up in the 2 oz bottles from US Plastics and 1 in 4 I have mixed thin -- just for crack repair. Needless to say most of the thin stuff gets tossed well before it gets used.

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Jim Howell
Charlotte, NC