Hide Glue

[Kennyz55]

Can this be repaired with hide glue or do we need to add a biscuit? How would you fix it?

[Pete Jenner]

So much for scarf joints. What happened to the truss rod?

[Kennyz55]

A "professional" was tightening it for the guy that sold it to me.

[fscotte]

Take the truss rod out or as much as you can and fit a nice snug piece of carbon fiber rod in there. Epoxy it. I don't see how glue by itself is gonna do much.

[sunburst]

If all that old glue can be cleaned off, if the pieces can be made to fit together very well, and if a way can be found to clamp the pieces securely and accurately during drying, hot hide glue has about the best chance of any glue or adhesive of holding that long term.
I would not recommend dowels, splines, or any introduced mechanical fasteners, I would not recommend any other glue or adhesive. It looks like a mandolin that is not of high value even un-broken, so no "heroics" are in order, just glue it and let the joint last as long as it lasts. If well cleaned and fit, that could be a long time with proper care and good luck.
Perhaps a new back strap would add some stability, but it's a lot of work.

[pfox14]

I wouldn't use hide glue. Titebond would be the way to go.

[Lefty Luthier]

I suggest removing as much of the truss rod as possible and installing a section of carbon fiber rod using thick super glue. If the pieces are clean and fit together closely (no missing pieces) use fairly thin hide glue and press together firmly. Let it sit for a couple of days and then hope for the best.

[Jeff Mando]

I wouldn't use hide glue. Titebond would be the way to go.

I second the Titebond. I worked at a vintage guitar shop and had the "pleasure" of fixing hundreds of similar breaks. My two main guitars, both Gibson electrics were repaired over 20+ years ago and have shown no signs of coming apart. Just glued with Titebond, no splines or anything.

The old guy who taught me repair, said the "hot hide glue pot" was something customers expect to see when they walk in a repair shop, so that is its purpose--tradition. But, when the customer leaves, the luthier gets out the Titebond and does the repair. I'm not a builder, so you builders might chime in on the advantages of hide, but I was taught that it was outdated technology.

[fscotte]

Well the harder it is to use, the better it is....

[sunburst]

...you builders might chime in on the advantages of hide, but I was taught that it was outdated technology.

I was taught that too, as I think many of us were. I'm pretty sure I've tracked the source of that to the companies making and selling modern adhesives. I was also taught that I would go blind if... well, never mind, must not stray too far from the subject...

When (not if) that mandolin is left in a hot car in the summer, that peghead is coming off of there if it is glued with AR (Titebond). AR also is more prone to cold creep than hide glue. Hide glue is less visible in the joint and is easier to touch up with color (probably not a high priority in this repair), but the bottom line is; a good joint is the important thing. If it is well cleaned, well fit, well clamped, and well treated afterwards, it will probably be fine with AR.

[delsbrother]

In Dan Erlewine's old series of broken headstock vids, he puts so many splines in to reinforce the break when he's done there's more spline than original neck. Is this no longer recommended practice? (I've never done one either way; just curious).

[sunburst]

This one isn't really broken, it is a separated glue joint, and from the looks of it, with all that old glue in there, it was never particularly well fit. Once again, if it is well cleaned, well fit, well clamped, and well treated, simply re-gluing it will make it better than it apparently was.
There are places for splines, especially when wood is fractured across the grain so that there can't be a good glue joint, but they are a lot of work and expense, and they add no strength to a good glue joint unless they fit better than the glue joint itself. It's a tall order to fit a spline better than we can clamp two flat surfaces together.

[CedarSlayer]

I have to entirely agree with John (sunburst) on this one. Hide glue is the one I would trust. Hot hide glue is not that hard to use, and it makes a repairable, reversible, removable bond. If you have done destructive tests and comparisons and used the best environment for each glue, you learn one important thing. The only glue you can trust is one that you have tested and know how it behaves. If you buy 5 pounds of a good dry hide glue, it will last you a very long time. Unlike other glues, hide glue does not go bad on the shelf. It has a relatively short shelf life once it is mixed, but the rest of the glues lose over half their strength in a year. So you can go batch to batch and never be able to entirely predict your glues behavior or you can invest in a quality supply of safe strong glue. The same type of glue that all quality violins, cellos, bass, violas, .... are made with. Most of the luthiers in the world cringe at the thought of having an instrument glued with anything but hide, fish or rabbit glue. All museum experts on preservation cringe at the thought of having something repaired with anything but hide, fish, rabbit glue or shellac.

For best strength here is the process, First remove the old glue and sand a bit off both surfaces using sandpaper on a flat surface. Make sure you have two totally flat surfaces with no glue. If this had been hide glue you wouldn't have to worry, but modern glues with few exceptions cannot be glued to with strength once they harden. You don't have to worry about shortening the instrument a touch since it is on the top side of the nut.

Then with the wood warm to the touch but comfortable, brush thin hide glue onto the surfaces to glue and let that dry overnight. This is called sizing and it increases the strength of the bond since it can properly bond with the wood and it will slow the wood from taking the water out of the glue bond being made, allowing the bond to become it's strongest. Then make sure you can clamp easily, warm the wood, and cover both sides of the joint with hot hide glue and clamp quickly. Leave it clamped overnight.

After this is all done, you can remove the excess glue with a warm damp but not wet rag.

Bob

[Nevin]

Hot hide glue is the way to go. Titebond is a good glue but all white glues have the potential to creep under pressure.

[Kennyz55]

Used the hide glue. Very difficult to clamp.

[delsbrother]

This one isn't really broken, it is a separated glue joint.

Oops, sorry, was browsing on my iPhone and didn't look closely enough.

[CedarSlayer]

Used the hide glue. Very difficult to clamp.

Most glues, white, yellow, epoxy and hide are slippery so there is no issue there.

All of these glues will squeeze out of a joint, so there is no resistance. The only issue I can think of is that the setting time on Hide glue is pretty quick unless you warm the wood first. I use a heat gun, a hair dryer would do. In the old days they kept the parts intended to be glued near a stove.

The odds are any glue that you used apart from CA would have been hard to glue and left you with a bad joint. Fortunately if you have a bad glue job with hide glue you can scrape it close to smooth and do it again with no issues.

The first thing you do if you want to glue well, is do a dry rehearsal. I have at times spent more time carving the supports for gluing than I have for the parts I was going to glue. Structure that allows for solid and stable joint holding is part and parcel of fine craftsmanship.

An angled wood joint like the one that broke, allows for more glue surface so you have a stronger weld. Angled wood joints want to slide as you compress, so you need some quality jigging no matter what glue you are using. While I agree with John entirely that adding dowels or biscuits will not strengthen the joint, something that might act as a key, so the scarf joint does not slide, might be helpful.

If the joint is bad, Try again. That is something that Gorilla and Tightbond will never let you do.

By the way, my advocacy for hide glue is for hot hide glue, the bottled stuff can still be removed and redone, so it is not bad, but it goes bad on the shelf, like the other glues do, so you really cannot trust it.

With hot hide glue, bad glue joints are all my fault, but I am allowed redoes.

Bob

[Rob Grant]

Try "keying" or locating the slippery devil with two or three short metal pins made from any stiff wire. I use short "stubs" of 2mm stainless steel TIG wire to make sure those slippery fretboards locate on my mandolin necks. Pre-drill slightly undersized holes in the neck glueing surface and carefully tap the stubby pins in leaving a short pointed portion just barely projecting from the holes. Without glue, exactly line up the two pieces to be joined and press them together. The point of the pins will leave a corresponding mark in the opposite part. When you go to glue the joint up the pin points should keep the joint from sliding out of position under clamping pressure. If you really want to make sure the joint can't slip drill a corresponding hole where each mark is, pull out the pointed stumps you used to create the marks and replace them with longer pins. Just don't get carried away and drill right through to the outer surface; keep the pins short.

[Kennyz55]

Learning a lot. How to use hide glue. How to make a bone nut. How to make a maple bridge. Really enjoying the learning process of my playing is taking a toll.

[High Lonesome Valley]

Whatever glue you decide to use, you might want to consider very carefully roughing up and scoring the surfaces so as not to actually start carving the surfaces, stopping just before the edges so you don't cut through the edge. Standard fare when I was a commercial luthier. I use a very sharp knife, cut/score X's cross grain, don't cut with grain.

Seen this at the Martin factory in the 70's, used it in luthiery and woodworking. It increases the working surface and uses the roughed up wood as a fibrous interlocking strengthener to the glue joint. Here's a recent thread on the issue. http://www.mandolincafe.com/forum/sh...-mando-content

Me, I'd use epoxy on this one, the slowest setup time with the greatest psi. Just make sure you push the epoxy well into the roughed up joint surfaces, mineral spirits cleanup. You can float a boat with epoxy and 180 degrees in a hot car won't be an issue. Slowest setup time to deal with the joint slippage, which is a PIA whatever you use. Really clean the epoxy out of the joint after clamping, you don't want to have to deal with it bulging out cured.

CedarSlayer mentioned the dry run. Right on.

Looks like matte black finish? Sand down joint after filler but just a surface sanding. Hand apply black sandable car primer (sprayed into the lid of the can) to fill joint pits and hit with maybe #300 wet dry sand paper at a 90 degree angle to joint, overspray with like paint from a spray can. The reason I would maybe not fill the crack with paint versus primer is because this is a neck joint, can't use safety razor technique, gotta sand, and sandable primer is much easier to remove to surface than regular paint. The reason I would sand the sandable primer at a 90 degree angle is so as avoid sanding down the surrounding paint as much as possible. If you had to sand through the paint on one joint due to uneven jointure, do it AFTER filling in crack with primer, using #300 wet/dry and plan on overspraying with a clear coat to seal before finish black coat.

For overspray, I would powder coat several times to build up a grainy surface, then do only one standard coat which would fill in the surface nicely, but prevent the need to sand/paint/sand/paint ad infinitum.

I don't use regular wood filler on these repairs, it's overkill and would set up a whole new set of problems. Just use spray paint, sprayed into the cap of the can, dried to a gel and painted into the crack or whatever with a sliver of wood, build it up until it's higher than surrounding paint, then sand.

[bernabe]

I wouldn't score or rough it before gluing.

[Rob Sharer]

Not sure how anyone is supposed to use this thread to decide which glue to use.

This, however, might be of some use:

http://www.frets.com/FretsPages/Luth.../gluetest.html

Frank Ford's test shows the perils of using Titebond for this repair; under real-world conditions, there is a real chance of failure.

I would add that, unlike Titebond, hide glue reactivates itself in a re-repair situation, unlikely as that is with a good joint. It is my choice for this repair.


Rob

[Michael Weaver]

Okay....am I seeing a strap button installed on the scroll?

[Jim Adwell]

http://www.frets.com/FretsPages/Luth.../gluetest.html

Frank Ford's test shows the perils of using Titebond for this repair; under real-world conditions, there is a real chance of failure.

Yup. If you're gonna put that mandolin in a 200 degree oven you definitely don't want to use Titebond.

On the other hand if you're planning on playing it while scuba diving, you'd want to use Titebond III, or better yet marine epoxy.

[PaulBills]

Okay....am I seeing a strap button installed on the scroll?

And that's the major problem with this?