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Old 01-11-2021, 10:27 AM
NeilG NeilG is offline
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Default Humidity crack, now to tight for glue.

My 7th acoustic build has just developed a low humidity crack in the European Spruce top. I intended to glue and cleat it but since hydrating the guitar, over the past few days, the crack has close up so tight I canít see a way of getting glue into it.

Question, would you just cleat it without gluing the crack or dry the guitar out again just enough to open the crack to get some glue into it and then cleat it?
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Old 01-11-2021, 10:36 AM
JERZEY JERZEY is offline
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Find yourself a plastic bottle with a slotted tip. Load it up with glue. You should be able to force the glue through the crack. You will know it worked if you see glue coming out of the back side of the top. It does not always work but its worth a shot.
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Old 01-11-2021, 10:45 AM
J-Doug J-Doug is offline
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Quote:
Originally Posted by NeilG View Post
My 7th acoustic build has just developed a low humidity crack in the European Spruce top. I intended to glue and cleat it but since hydrating the guitar, over the past few days, the crack has close up so tight I can’t see a way of getting glue into it.

Question, would you just cleat it without gluing the crack or dry the guitar out again just enough to open the crack to get some glue into it and then cleat it?
In Dan Erlewine's repair book it suggests reaching into the soundhole and pressing lightly on the crack with your finger to open the crack somewhat for gluing. He then suggests rubbing the glue back and forth perpendicular to the length of the crack on the exterior surface of the top as you press the crack open.

Watch the first minute or so of his video:

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Last edited by J-Doug; 01-11-2021 at 11:06 AM.
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Old 01-11-2021, 11:07 AM
L20A L20A is offline
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Some Techs use a small suction cup to force glue in the crack.
Run a bead of glue along the crack and then use the suction cup to force the glue into the crack.

Now use a strap or clamp to pull the sides of the guitar together and let the glue dry.
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Old 01-11-2021, 11:17 AM
Scotso Scotso is offline
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Quote:
Originally Posted by L20A View Post
Some Techs use a small suction cup to force glue in the crack.
Run a bead of glue along the crack and then use the suction cup to force the glue into the crack.

Now use a strap or clamp to pull the sides of the guitar together and let the glue dry.
yup. If you put a bead of water on the crack first and let that wick into the crack, it will help pull the glue in.
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Old 01-11-2021, 01:34 PM
NeilG NeilG is offline
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Thanks for help gents, this crack is tight, but I think I’ve got a plan now. I’m liking the sound of bead of water and the suction cup to help pull the glue in, I’ve got really good pump suction cup that should do the trick. I’ve also ordered a couple of decent rare Earth magnets that I’ll use to position and hold the cleats - we’ll see how it goes ��

Last edited by Kerbie; 01-12-2021 at 02:07 AM. Reason: Please refrain from profanity
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Old 01-11-2021, 05:05 PM
Earl49 Earl49 is online now
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I would actually worry about thinning or contaminating the glue with too much water. Watery glue likely won't be as strong, but I'm not an expert. Perhaps you would get a more authoritative response if this thread were moved to Build & Repair. Just ask a moderator to move it. Click on the red triangle on the right edge of the blue bar after the post number.
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Old 01-11-2021, 06:27 PM
mirwa mirwa is offline
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No finish yet?
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Old 01-11-2021, 06:51 PM
Carey Carey is offline
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> I intended to glue and cleat it but since hydrating the guitar, over the past few days,

There are plenty of unknowns here, but seeing what your wood wants to do in
an un-artificially hydrated state would be a good thing to look at.
It cracked for a reason..
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Old 01-12-2021, 02:51 AM
NeilG NeilG is offline
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No finish yet?
Yes itís finished, Iíve been playing it for about 2 months.
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Old 01-12-2021, 04:47 AM
mirwa mirwa is offline
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What type of finish did you use?
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Old 01-12-2021, 10:03 AM
NeilG NeilG is offline
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Nitro lacquer, same Iíve used for 30 years with an issue. Iím leaning towards the possibility of a weak soundboard and rapid dehydration, but Iím only guessing. Iím about to glue and clear it, Iíll see how it holds up after that.
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Old 01-13-2021, 06:01 PM
mirwa mirwa is offline
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Being nitro and a soundboard, I would use hide glue, as hide glue dries clear, if it was a poly finish i would have considered ca glue
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Old 01-28-2021, 04:55 PM
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ArchtopLover ArchtopLover is offline
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Default Suction Cup to the rescue.

Quote:
Originally Posted by L20A View Post
Some Techs use a small suction cup to force glue in the crack.
Run a bead of glue along the crack and then use the suction cup to force the glue into the crack.

Now use a strap or clamp to pull the sides of the guitar together and let the glue dry.
Agreed, this method works well.

I believe I first saw Jerry Rosa of Rosa String Works, use this crack repair technique on the YouTubes, a number of years ago. He said it was an old violin makers repair trick. I keep three different sizes in my guitar tool chest and use them often.
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