Releasing "Gorilla Glue"

[JLeather]

I have a mandolin that had the back separate. The quick fix at the time was to reattach it with "Gorilla Glue". Time has passed and I'd like to remove the back and fix a few other things including the fact that when it went back on it was slightly misaligned. Does anyone know how to dissolve Gorilla Glue?

[David Collins]

You don't use polyurethane glues for things like this. You just don't. Hopefully this was just a cheap flat top or import, which if this is the case I'd say live with it and write it off as lesson learned. If it is anything vintage or of value take it in to a professional, which judging from how you approached the initial repair, would have been wiser to do to begin with.

Gorilla glue does not release well by heat, moisture, or any practical, safe chemical means that I know of. By using it here you have made any future repair much more difficult, and likely much more expensive than it would have been to do it right the first time.

[barry k]

Jleather, since you say the back has to come off anyway, no harm done. You need a good grade Japanese pull saw, then just cut the back off along the binding line all around the back of the mandolin, just dont use gorilla snot when you put it back together. Why DO you want the back off anyway?

[sunburst]

Now that you've endured your stern lecture on appropriateness of adhesives in instrument repair, the gorilla glue will have to be physically removed. Is the gorilla glue in the center seam of the back or the back to rim joint? If the later, it's manageable, if the former, you've got a mess there.

[JLeather]

I want to take the back off because when it went back on it was a little crooked. It needs to come off, have all the binding removed, and be made to fit again. Then reglued, recut for new binding, and have the binding installed.

Here's the deal on this mando. I bought it new from a builder out in Kansas, Cecil Sullivan. I don't know if it was poorly cured wood, or old hide glue, or what have you but I only had it for a couple weeks/months when the back just popped off at the neck end. I opened the case one evening and picked it up and the back was just hanging there. It was my only mando at the time, and I needed it playable. There must have been some stress relieved when it came off because it wouldn't go back on quite right, and like I said I needed it playable, so I used gorilla glue because it would fill the gap and I figured it'd hold (apparently I was atleast right on that front). Not proud of the job I did, but it returned to playability for a while til I got a better one.

At this point it's sitting in the corner of my closet, and if I can't fixit up a bit better it will remain pretty much worthless. So I figured now that I have more time, and nothing to lose, I'd take a shot at a better fix. I do a fair bit of cabinetmaking, including a nice toboggan a couple years ago although no instrument making to date, and I thought I'd see what I can do. If I completely ruin it doing this I'm not out any more than I am right now, except a couple hours time.

Actually, it's in pretty sad shape at the moment, which is a shame because it's a got some real nice walnut for the back and sides (bad finish though). It needs a fingerboard while I'm at it too because it has too much radius for my taste. It's gonna be my winter "maybe I can fix a mando" project.

So, if I'm hearing this right, I should cut it around the sides where the binding meets the side? Won't the leave the sides a little shorter than they were before? Suppose that doesn't matter since I'll have to massage the back to get it to fit again anyway. I actually have a good pullsaw. I use it for cutting off dowels when I plug screws over and things like that. I was curious if there was a chemical way to release the glue, and the answer is apparently an emphatic "no". So I'll cut it apart and see where I stand at that time. Pics if I succeed

[Rick Turner]

I'd use a Dremel in a small router base with a thin circular saw blade, then use a very thin kerf Japanese pull saw (see "Japan Woodworker") at the neck and tail block. Saw just at or below the glue line of the back itself. Yes, you're going to lose about 1/32" of body depth. So what?

Then see Frank Ford's screw adjustable mando mold. You may need one if the body distorts much when you take the back off. Clean off all the old glue that remains, and if you really want to learn good repair techniques, glue the back back on with hot hide glue...or at least use LMI's white glue which has very low cold creep.

You may be able to get Gorilla glue to let go with heat, but it may take enough heat to scorch the wood.

Also, what is the humidity in the environment where you keep the mandolin? That could be a factor if it's too low.

[MikeEdgerton]

Won't the leave the sides a little shorter than they were before?

Yup. You have limited options, that stuff isn't made to come apart like other glues.

By the way Barry, Gorilla Snot and Gorilla Glue are two totally different animals.

[bennyb]

Howdy Leather,
Here's a photo essay of Brian Kimsey sawing off a back and putting it back on. I haven't done it myself.

good luck, benny

[Mario Proulx]

When testing adhesives for spruce to carbon fiber laminating(IE: my guitar braces), polyurethane glues were the only ones that were unaffected by heat in any manner. Even when sprung, the brace would catch fire and burn, eventually folding over, and the poly glue never let go. I did have to remove a aluminum U channel truss rod that was poly-glued into a guitar neck, and for this one, I drilled and tapped for a small bolt at each end, attached my big gauge jumper cables to them, and connected them to a fully charged, 1200 CCA battery. Within seconds, I had smoke, pulled the cables and with welding gloves on, I pulled the rod out of the neck. The glue more or less held, as it was the neck's wood that was weakened by the intense heat. I have photos of that operation somewhere on my site...

Bottom line; as everyone suggested, you're going to have to saw that sucker off of there.

[barry k]

What ?????? Gorilla glue and Gorrilla snot are not the same thing , now Im totally confused.............yea Mike I knew that, bad choice of words, but non the less , I dont like either product too much. When ever I had a problem to keep a pick in my fingers, I just smeared some salve on it from the fiddle players bridge.

[barney 59]

I have used gorilla glue for a lot of different applications (but never for musical instruments). While it claims to be the "strongest glue on the planet" it just might possibly be the weakest glue on the planet.That is my conclusion after many years of working with it. It is possibly the only good solution for situations that require glueing wet or green wood and in those situations I will continue to use it . It prefers moisture to set properly so if you didn't wet the wood before you used the glue you may have lucked out and created weak joints. If it wasn't clamped properly then it tends to create these foamy joints that in fact will cut like bread. The areas where you said it would fill a void should be the easiest to cut -this might not be that great of a disaster after all. The suggestion of a thin kerfed blade , that and slow patient going would be my suggestion as well.

[Mario Proulx]

<sigh>


As with any product or item, proper use is always what makes or breaks it. Poly glues don't fill gaps, so yes, poor fitting joints will be weak. Poly glue requires a minimum of 6-8% MC, so yes, if the wood is too dry, the joint will be weak. Because of the strong foaming action, if it isn't properly and evenly clamped, it will be a weak joint. Yup, if you're sloppy and can't read directions(the part about wiping the joint with a damp cloth, and/or strong clamping required, maybe?), it will be the weakest glue on the planet; for everyone else, it will be just fine, very strong, and can't be reversed, short of sawing the joint open.

[violmando]

My very first year of teaching stringed instruments in schools, one of the parents had glued a crack under the tailpiece of a cello with super glue. He did this the summer before I got hired; one day the daughter brought it in with the entire table of the cello collapsed down there....the crack held, needless to say, but the rest of the wood gave way when the weather changed....it was an EXTREMELY expensive repair and the school district made them pay for it. I told that story to future students from then on so that other parents would NOT undertake their own repairs.....

[jonkka]

Get an Xacto razor saw. It's like a razor blade with teeth. Almost no kerf removed. It's smaller even than a Japanese crosscut blade.

http://www.amazon.com/Xacto-X75300-P.../dp/B00004Z2U4

[Lefty Luthier]

A word of caution when sawing a top off, check if there is a Verzi. I'm sure all can guess how I came to this conclusion.

[Stephen Lind]

???Huh???

[Stephanie Reiser]

???Huh???

If the "huh" is refering to the word "verzi" usually spelled "Virzi", this is a wooden piece glued to the top plate. THe author of the post was probably concerned about the saw damaging it. This is a not so good photo of one I made.

I know of one particular school of guitar building that teaches students to glue the fretboard on with Gorilla GLue. Ugh.

[Stephen Lind]

It wasn't the spelling or that there was one

[fishtownmike]

Hammer?

[Gail Hester]

Usually sawing the back off is the way to go even if the work needs to be done on the top. I've sawed/sawn lots of backs off with a .010" kerf blade without even disturbing the finish but never a top, maybe I'll find a reason some day. If you saw the back off, take the glue line and a tad of the rib and take nothing from the back itself.