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This is a pic of a guitar I built that a customer bought at a dealer recently. It was deliverd to the dealer about 2 months ago. You can see the raised ridge along the top center seam behind the bridge. It was definately not there when I dropped it off. The guitar was about 2 months old when I delivered it. The finish is z-poxy over french polish. I have not had this happen before with this finish and suspect it has been exposed to a very dry enviroment. The customer is happy with the guitar but is concerned about the center seam ridge (and so am I). Any wisdom would be appreciated. TIA.

Here's another pic for comparison.

Guess it just ain't my day. Center seam from "above".

Paul, my guess is the same as yours,poor climate control at the dealer's. Either that, or you've got a possible glue failure in the joint. Do you have good center seam supports?

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Paul have you looked at the inside to see if you have the same effect on opposite sides or is the inside OK?

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Kenmore, NY 14217
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I haven't seen the guitar yet. The customer sent me the pics. He says the inside is okay but I won't know for sure until I see it in person. It really looks like the wood has shrunk around the seam and the glue joint resisted shrinkage. Looks like the finish ridged up to me. I am very carefull about humidity especially when doing body work, I keep it as close to 42% as possible.

I put small spruce "diamonds" between the lower face braces and before the tail block, and after the bridge patch like a lot of people. It just doesn't look like a seam failure. Hopefully I'll get a chance to see it in person. The buyer isn't that worried but wants reassurance from me and the only way that can happen is for me to see it in person.

Any chance they dropped it?

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

It's possible I suppose that it was dropped. That brings up some not so nice warranty issues about who is respsible and when. This is just a good incentive to do my own web page and marketing. I just have no control over a guitar once it goes to a dealer.

What kind of glue did you use on the book match joint? I have seen this happen with Titebond as the glue will show a witness line.

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tim...
http://www.mcknightguitars.com

I have heard of this with some kinds of glue. I guess maybe some glues continue srinking and if you thickness the top to soon before the glue has shrunk completely this could happen. Mario will tell you to use hide glue and I'm sure that would be an advantage. I have been using the LMI white glue. I have a batch of hide made up but have not tried it yet.

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Paul, I'm curious like Tim, was this Titebond? I've had one guitar do it as well. That guitar hasn't been subjected to much in the way of dry conditions or hot temps.

While I love Titebond, I suspect it as the culprit, as Tim does. Clamping methods on your top join may have left a bit too much glue in the joint. So any shrinkage of the top, and we all know they continue to shrink and expand, for their entire lives, depending on humidity. I really suspect it to be a squeezed glue joint.

I've changed my method for joining tops. I now use the tent method and about five strips of tape drawn tightly across the joint, evenly spaced across the join perpendicularly. Flip the top over, run a bead of glue in the vee-shaped cavity, allow the top to flatten against the work table and remove excess glue. You could just weight it and leave it, but I like adding tape strips to the back as well.

I think Mario may use some variation of this too, and many use hide glue for this critical join. I've used both glues. Here is where notations on the build sheet could pay dividends later.... good luck with the problem, I have one to repair as well down the road. Fortunately mine is in the family and no one is worried about it.

Titebond, or other similar glues, will do that. The glue remains plastic forever. The waterproof Titebond II and III are worse. What you're seeing is what happens when a join glued with PVA glues sees a fluctuation in RH. The two halves here are expanding(nothing wrong with that, except...) and are "squeezing" the plastic glue out of the joint. Fun stuff, eh?

Hide glue rules!

[QUOTE=Mario] Titebond, or other similar glues, will do that. The glue remains plastic forever. The waterproof Titebond II and III are worse. What you're seeing is what happens when a join glued with PVA glues sees a fluctuation in RH. The two halves here are expanding(nothing wrong with that, except...) and are "squeezing" the plastic glue out of the joint. Fun stuff, eh?

Hide glue rules! [/QUOTE]

This is one of the reasons that I use Hide Glue to join my tops and backs, I also use it on all my braces (including the X joint), it's not hard to use at all and not only is it stronger than PVA's but it's more durable as well. In fact Frank Ford did some very interesting tests using an oven

Now I do use LMI white glue elsewhere but in the critical spots I don't think anything beats a good hide glue joint, plus unlike the current crop of glues I can show you a number of instruments built with it that are still around after hundreds of years....

-Paul-Sprockett38373.0528703704

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-Paul-

Patriot Guitars

I actually bought the top already thicnessed and joined. It was before I owned my own thickness sander and had to borrow time on someone elses machine.
So the answer is I don't know what kind of glue was used but will try calling the seller and find out. I have been using hide glue myself for this joint.

To me this is a classic case of over drying. Humidify that guitar a.s.a.p.

I have a Martin guitar that the center seam opens up by about 1/16" if I let it dry out....which it did before I had a handle on my shop humidity.

I think that the reinforcing diamonds are over matched when it comes to severe shrinkage.

sorry to hear about the trouble Paul, been there.
Matt

Thanks for all the responses. I feel a bit better. The buyer actually did the first thing I would have done and gave it the "flashlight" test to check for gaps in the seam. It looked okay to him. I love knowlegable buyers!
It looks like pretty much a cosmetic thing agravated by low humidity and/or the glue used. I'll probably never know for sure. The joined top was over 1 yr. old before I used it so it may be useless to call the wood guy.
The lesson learned is to do all my own work, at least then I know the complete history and process used. I have avoided so many mistakes by raading forums like this that I guess I was due to contribute the hard way.