Peghead Veneer Cracked

Took the clamps off after gluing the veneers to the top of the peghead and the ebony plate was cracked the entire length. Used clamping cauls so not sure what happened. Used LMI White glue. What would be the best way to remove?
Thanks for your help!
Mark

Laidback1 said:

Took the clamps off after gluing the veneers to the top of the peghead and the ebony plate was cracked the entire length. Used clamping cauls so not sure what happened. Used LMI White glue. What would be the best way to remove?
Thanks for your help!
Mark

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Glue another thin one over it.

a heat gun and a razor blade, or other thin edged tool. Heat softens that glue nicely.

What species of wood was the peghead itself? I wonder if the crack was present beforehand, but invisible, or if the moisture in the glue caused an unequal swelling which caused the crack. Or if the Ebony veneer was not dry/ stable enough..

Neck/Peghead Honduran mahogany. The Ebony has been in my CC room for several months. Like you said, it could've already had a crack that is just now manifesting itself. Oh we'll, gonna get out the old clothes iron and thin bladed tool....
Thanks!

Laidback1 said:

Neck/Peghead Honduran mahogany. The Ebony has been in my CC room for several months. Like you said, it could've already had a crack that is just now manifesting itself. Oh we'll, gonna get out the old clothes iron and thin bladed tool....
Thanks!

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I am so happy that you are removing the cracked headstock veneer..I do not know if you are building your uke for a customer..but it shows that even though no one except you would of known if you had some how covered it up instead of replacing it...the one person who should care the most is You..

I know other Luthiers that will never let any mishaps leave their shop with a hidden mistake..I think it is called pride in their craft...

i don't know you but i will watch your post on the UU and track your building career..good luck!

Why the LMI glue?

In that situation, you'd be much better off using either epoxy or a polyurethane glue.

You added water to the glue line, the ebony swelled and then it shrunk and cracked.

So what else is new in this world?

Read my rants on glue...what I use, where I use what, why I use what.

You have to think about these things, and each and every glue joint in an instrument should be thought out and the appropriate glue used. With some the moisture issue isn't a problem...with some it is. This is how you learn what works and what doesn't. What you did sometimes doesn't work, and the "why" of that is not hard to understand.

Water...

Swelling...

Shrinkage...

Crackage!...

that is what I think too. I have seen a couple similar failures when using water based glue, which is why I do not glue dense exotic veneers with water based glues. I have seen the cracks form a month or so after gluing, and I am certain that it was because of moisture from the glue, not unseasoned wood.

and a cover veneer would have left a tale for anyone who looks closely. Easy to remove the cracked one.

Chris_H said:

and a cover veneer would have left a tale for anyone who looks closely. Easy to remove the cracked one.

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Not always, just sand the cracked veneer down thinner, fill the crack and glue a thicker piece on top. You could even use the original ebony so it appears as a black line under a lighter colored top plate. s** happens, its time to get creative when it does. This kind of stuff is going to happen.

It's not going to happen if you understand the nature of gluing wood, anticipate issues like swelling from large areas of water based glue, and then use appropriate adhesives.

BTW, I have a circa 1825 French or Austrian guitar with a laminated back...spruce on the inside, walnut on the outside...a common practice in the early 19th century. The back is so badly warped that it opened up the center seam to the point where the only save is going to be removing the back and damp heat treating the whole thing in a vacuum press to maybe get it flat again. Why did it do this? Same reason as your peghead veneer crack...and an unbalanced layup which is much more of an issue with water borne glues.

This is not a new problem for luthiers, cabinet makers, or furniture makers. It's probably as old as glue itself.

I find that with epoxies or polyurethane glues, the whole issue of "balanced layup" is not much of an issue. But then again, I seal all my exterior wood surfaces with epoxy before finish, so the potential differential swelling and shrinkage from climactic changes is greatly reduced.

I find that with epoxies or polyurethane glues, the whole issue of "balanced layup" is not much of an issue.

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What brand of polyurethane glue do you recommend? Do any particular brands have minimal foaming?

I've had this happen to me twice before with ebony but the crack only became obvious after the finish was on and while the uke was being buffing out. I attributed the cracking from using water based glue made worse by the intrusion of water into the tuner holes during the wet sanding process. (The cracks had originated at the holes.) I now go with the smart money and use epoxy for laying up my head stock veneers.

All of the polyurethane glues foam, so you have to use them where that won't be an issue. I find the Franklin's product to be the least problematic. Also, we don't use additional water to kick the poly glue (water acts as a catalyst for polyurethane glue). The natural 6% or so of MC in the wood is sufficient, and we just let it cure as long as it needs.

We don't do a lot of wet sanding on our polyester top coat finishes, so the problem Chuck describes...which I do know to be an issue...doesn't come up for us.

I wouldn't scrap it. Ebony is so easy to fill with a mix of CA and ebony dust. Its not a functional or stressed part of the uke so it shouldn't be a concern.

Sorry, but that's not necessarily the best advice: the repair may very well telegraph through finish, in fact, it's a probability. If a perfect finished surface isn't the goal, then try it, but don't be surprised if it shows sooner or later. Note that the solvents in nitro lacquer are also solvents for CA, so you are likely to get some sort of reaction there. If this were a finished or vintage instrument, I might try a fill repair, but on a new build...well, I wouldn't do it like that. There are underlying issues of stress in that wood, and I don't think it's unreasonable to expect more movement of the wood, especially if the instrument goes to a dryer climate at any time.

Ok, bought a cheap iron from WalMart and used it and a palette knife to remove the cracked veneers. Scraped the residual veneers and glue with a razor blade and quickly sanded. Rick, great info on not using water-based glues on this operation. Will search the forum for your writeups on what glues you use where....
Ordered some new veneers and some Steve Smith Wood Epoxy from LMI today and will have another go at it when it arrives. Oh, FYI this current build is a Honduran Mahogany/Sitka OM guitar. This is guitar number four. When I finish this one up will tackle my first ukulele. Thanks for the help folks!
Mark

Don't blame the glue, it's the technique. Counter the swelling of water based glue by using a damp cloth on the reverse side. I haven't used CA, Epoxy or any other non water based glue in over 30 years and haven't experienced that sort of cracking, other than on difficult curved veneer projects. They cracked in the bending, not the gluing.
Rick's 1825 laminated Guitar. I've seen literally hundreds of them. Many of them exhibit cracks, some don't. Not so much the glue. They are usually a thin exotic wood laminated on to thin Spruce. Then think 200 years and no humidity control. Some of my laminated Backs are now going on 10 years old and I haven't had one single crack reported. All glued with water based glues.

not sure I am buying that, as simply as you state it. I have seen some exotic veneers survive with water based glue, and a couple crack, none since switching to non water based glue. Regardless, it makes more sense to me to use epoxy, or another glue, depending on the application, then to introduce more water into the equation.

If you have a recipe that works, excellent. Hopefully you can explain why I am wrong, in detail.

The moisture on the reverse side, as you say, to me sounds like the same recipe as '200 years with no humidity control'. Based on my observations, and I have only theories still, nothing absolute, I think that in the glue up, there is an immediate swelling, different woods and substrates will swell with exposure to moisture, differently, then, with the '200 years of no humidity control', and all of the water moisture, and probably some additional shrinkage of the cellular structure, the wood is under stress. If the wood is under a lot of tension, like a mixed grain, or a wood that is more reactive to moisture, some other unseen stress, it may crack. Maybe it is a few hours, maybe it is a few months. (like with 2.5mm Cocobolo veneer) You can take 10 different pieces of Ebony, glue them to 10 different pieces of Mahogany with water based glue, how many will crack? 2? 4? none? Woods move when glued, less with epoxy, or resin based glues, then with water based glues. Yes, absolutely, water based glues cause swelling in wood at glue up. In gluing things like an Ebony veneer to some substrate with a water based glue, there is a range of glue amount that will give a successful bond, and using the absolute minimum amount will help minimize cracking/ movement in the wood at glue-up.

Personally, it is so much less work to me to mix up some epoxy, or resin based glue, then it is to remove and replace a cracked veneer.

quartersawn Ebony veneer at 1mm is one thing. Mixed, swirly figured Rosewood at 2mm is another. Sometimes it is hard to see what is inside a piece of wood.

I'm relating my experience of over 30 years of making Guitars using water based glues. The moisture on the reverse is to counteract the tendency for the wood to curl. it actually places less stress on the wood. The exact same principle as hammer veneering. I have never used Epoxy or any other non water based glues on Guitars. I've also never had cracking of head veneers. Never. I think I've veneered the back of over 10 Guitar Necks. Not many but veneering the back of a Guitar Neck is way more stress than any simple head plate glue up. We stress wood an enormous amount. Much worse than a bit of water that happens to be in the glue. Think of bending Sides and the amount of stress that puts on it. In fact my first few Guitars were done by boiling them in a water trough. If water based Glues were such a problem (they aren't) I would have given up on them years ago. I suspect that the reason why the OP had a problem is that the veneer had a hairline crack in it anyway. I've long lost count the number of head veneers that I've glued up. Hundreds. Ebony, Rosewoods, Coco, figured Maple, figured Walnut etc. Never had one crack. Rick's 1825 Guitar is a little different. These are laminated Backs. It's not the water based glue that caused the problem (I've done loads) it's the fact that they are two very dissimilar timbers - Spruce and usually some exotic - together end up at around 3 mm's thick. thin and vulnerable material. Doesn't matter which glue you use. Lack of humidity control and 200 years is going to result in cracks.