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I've scratchbuilt 9 guitars, but I've never needed to learn many repair skills. Until today. The center seam on a spruce soundboard split south of the bridge. It was assembled with Titebond and the joint is open a few thousandths (barely visible). Heat hasn't been running much, humidity is roughly 40%.

Before I do something I wished I hadn't done, what to do? Finish repairs don't frighten me (satin Minwax nitro rattle can).

Thanks!

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Peter Havriluk

Hi Peter: It is suspect that the center seam below the bridge came open that is the single most common place for RH deficit cracks to happen. Here's what I would do but again I would be concerned that this guitar shows signs of perhaps being dry. 40% is on the low side and if it was built in say 55% that will be enough of a difference to make it RH sensitive going forward. How old is the guitar?

1) Get a car wash sponge and a large garbage bag (not an editorial comment on your building ).

2) Completely wet the sponge so it's soaking wet and place it in the bag being careful to not get the sides of the bag wet.

3) Place guitar in bag and tie the bag snuggly where the neck meets the body.

4) Hang guitar by the headstock on a hanger with wet sponge in the bag below the guitar and the bag closed at the neck joint. Leave it for 1 - 3 days checking daily for the crack to completely close. You don't want the sponge or water to ever touch the guitar. Our measurements show inside our bags to be about 75% RH if you are interested.

5). When the crack is closed remove the guitar from the bag and wash your hands. We wash our hands because Titebond original what I would use will carry dirt from your fingers into the crack and then the crack will appear darker. So wash the hands please. You don't need to attempt to clean up prior Titebond regardless of what anyone may say.

6). With Titebond I use two steps and this is my own method proven on hundreds of cracks that I've done.... wait.... I mix a little bit of Titebond Original with water, 50/50 and with one arm in the guitar I run a bead along the crack top side. The guitar is level on my bench. With the inside hand I pump the crack with my fingers and the capillary action sucks that bead of thinned Titebond into the crack nicely. When I feel wetness from the glue on my fingers inside the box all along the crack step one of the gluing is complete. Now immediately run a bead of full strength Titebond Original along the crack top side. Repeat the pumping of the crack with your fingers inside the box. You are trying to get the glue topside to migrate into a tight crack. I work the glue topside into the crack as I pump inside the box. the pumping from inside the box should be forceful enough that you can see the crack slightly open and close as you press and release.

Again when you feel little beads of the thicker glue on the inside of the top you have the glue well distributed in the crack. This method exploits watered down glue to encourage the thicker glue to follow into the crack and it works very well.

Once the crack has glue in it and will stay closed on its own I wipe excess glue inside and outside off and slap down waxed paper topside over the crack. You can use thin plexiglass, cutting board material, lots of things but I like it clear over the waxed paper as a caul that once clamped will level both sides of the crack to each other. Any clamps that go inside should have waxed paper on the business end or any cauls Titebond will not stick to waxed paper.

I use rare earth magnets and not the whimpy StewMac ones we buy ones that exert about 42lbs of pressure and can be a bit dangerous since they can jump. Or you can just use clamps, long reach clamps with the flat cauls to keep both sides level. One of the nice things about magnets is you can position them topside for where you need them inside where you can't reach.

I leave it clamped and glued over night and then remove clamps. Hot water cleans up excess glue. If you level well there is NO finish touch up necessary and since this is a center seam if you washed your hands the repair may be invisible and level.

But I remain concerned that it did happen when our furnaces have started to come on and this fall in Michigan has been exceptionally dry too....

Lastly I make little diamonds perhaps 1/2" long beveling all edges and glue them inside the box cross grain between any tone bars and such. These are cleats and insurance. Cleats can be Titebond too but there is an argument for a drop or two of medium CA as well. A cleat does not need to be serviceable.....

And really lastly it would not surprise me if the RH is not lifted where this guitar lives if it cracks again since this does sound like an RH crack to me.

Let me know if you need any help and PM me I am always happy to help.

Excellent thorough advice, Hesh.

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Guitar Maker and Purveyor of the World's Finest Tonewoods
http://www.aaronhixguitars.com/
http://stores.ebay.com/A-Hix-Tonewood-a ... r-Supplies

Oboy! A graduate course assiignment. Thanks very much. And Titebond in a separated Titebond joint? Guitar's a year-plus-some old.

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Peter Havriluk

Fantastic, detailed tutorial, Hesh. Very generous of you.

I'd be very interested to know if you have any further thoughts to share on why it works to re-glue the center seam on top of the original glue in the joint ("You don't need to attempt to clean up prior Titebond regardless of what anyone may say"). I assume you make that assertion based on experience -- that is, you've repaired many many center seams this way and they have stood the test of time. The proof is always in the pudding. Still, I'm very curious as to whether you have a theory or explanation, as it seems to defy conventional wisdom that you can't get a good glue joint without removing old glue.

In the same vein, I wonder if you use the same approach with any other glue joints, such as loose braces, or even re-gluing lifting bridges?

Thanks!
Todd

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

Hey Todd I hope you are doing great.

Yes it simply works the old glue does not have to be removed from a loose brace or a center seam. In fact you risk scope creep especially with the center seam where you may have to add wood, refinish, etc greatly increasing the costs of the job for the client.

We know what glue many manufacturers use such as Martin and it works fine with HHG or Titebond Original. I prefer Titebond original for a Martin center seam and we've done hundreds of them since we have repaired around 1,100 guitars annually for nearly 20 years now.

We guarantee our work and a reglued center seam or brace has never come back to us loose, not even one. If it ever does we repair it again at N/C but this has not happened.

The real world of commercial lutherie is vastly different than what some suggest here.

EDIT: I want to add where it matters such as a bridge we jump through our sphincter to clean up all old glue from both surfaces, expand both surfaces to around 0.005" of the bridge perimeter for maximum gluing surface, use only fresh HHG, preheat, have prepositioned clamps that can be secured in 10 seconds or less and that works great on bridges. Did I mention that we also fit the bridge to the top so that only light finger pressure has it down everywhere including the wings. Then we clamp the hell out of it.

Almost forgot we also rabbit our repair bridges so that the expanded wood-to-wood area is 100% in full contact since a flat bridge bottom is no longer attempting to span the finish ledge and losing wood to wood contact.

Point being the stress on a bridge is far greater than a center seam and we do relieve the center seam stress by rehumidifying the top until the seam closes on it's own. We also wait a few days to ensure that it stays closed on its own. The glue is insurance and not doing any heavy lifting.

Braces are also not under the stresses of a bridge so not cleaning out the old glue can work well in certain situations. Thankfully this works where a brace is tough to get to anyway.

Thanks so much for taking the time to share all these additional thoughts, Hesh. Illuminating and much appreciated.

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/