The recent thread on headstock repair inspired me to bring this up. In one of the posts, one of our members mentioned a fish glue repair that failed twice. When one of my suppliers first started carrying the stuff a few years back, claiming all the advantages of hot hide glue without the problems of heating and immediate clamping, I was sorely tempted. But I held off, because I had not heard of the stuff, and didn't know if the long term results would be good. Since then, I have heard of many fish glue failures.
So I thought that this might be a good time to talk about glues.
Here's what I know about glues, from personal experience over a period of many years:
1. Hot hide glue-- great stuff if applied under the right conditions. A bit of a pain, and there's a definite learning curve. But it doesn't creep, and can hold for many decades, sometimes even for a century or more. But it's a recipe for failure if you don't dot all the i's and cross all the t's. In many cases, easy to disassemble when necessary. High bonding strength. Non-invasive to finishes.
2. Good old Titebond Original. An aliphatic resin-- Easy to use. Reasonable open time. Breaks down at lower temperatures than hide glue, but not unreasonably low. Creeps, but not too much. High bonding strength. Hard to disassemble without quite a bit of heat. Non-invasive to finishes. Will hold for decades.
3. Cyanoacrylate, also known as CA or super glue. Bonds nearly instantly. Invasive to finishes. Rather unpredictable stuff. One luthier states "cooks in five years." Not suitable for structural repairs, but good for inlays, loose fret ends, fingerboard divots, and the occasional shimming of mandolin bridges, but not much else. Some people use it for bindings, but then there's the danger of marring a finish.
4. The various binding cements, such as Duco and the specialized cements available from LMI, Stew-mac, etc.-- Good for bonding plastic to wood. Invasive to finishes. One problem is that so many different plastics are in use these days, it's hard to know whether you've got the right glue for the plastic you're using. I have also used Weldbond contact cement recently for a pickguard replacement on an old D-28.
5. Epoxies-- A big can of worms. Difficult to clean up, difficult to break a bond if necessary. Most people will probably gravitate towards quick cure varieties available in hardware stores, which are often not of high grade. If I find it necessary to use it, I'll probably select a high grade marine epoxy, formulated with wood in mind. Limited usefulness in lutherie.
6. Titebond liquid hide glue. Some of the advantages of hot hide glue, but risky for structural repairs. If you use it, it must be fresh. A bottle must be discarded after a year, and I recommend it be stored in the refrigerator. I generally use it only for non-structural repairs. I like it for fret jobs and gluing nuts, or to make paste filler around inlays. The last new bottle I saw had a coded expiration date, which I don't like at all.
7. Old Brown Glue. Another semi-liquid hide glue. I haven't used it. Must be heated, but only moderately, and has a longer open time than hot hide glue. Lacks the preservatives that some say are responsible for Titebond hide glue failures. Old Brown glue is hide glue with urea added. Considering the expense and limited shelf life, I have instead chosen to make my own in small quantities. I haven't yet settled on the best proportion of glue granules to urea. The last batch I mixed used 10% urea. To me, this is an unproven glue, and if I use it, I must be prepared for do-overs.
8. Wilsonart Lokweld melamine glue. An unproven quantity. Made for bonding non-porous materials to wood. Used by cabinet makers for bonding Formica to wood. Non invasive to finishes. Modest bonding strength. An unproven glue in lutherie. A cabinet maker friend suggested I try it for repairing loose bindings on finished instruments after I complained about the difficulties of using cements or CA without risking finish damage. I've used it maybe a dozen times. So far, so good, but I understand that I must not be surprised if I have failures with it. If it proves to be good over the long term, it might be a great alternative for binding repairs. But again, it is unproven. I hope a few others will take a chance with it so we can find out whether it is indeed viable.
9. Other glues: Elmer's wood glue and white glues are polyvinyls, as are Titebond 2 and 3. Anybody who has worked on many 60's and 70's Martins knows that polyvinyls are a poor choice for lutherie. I will not bother to discuss Gorilla glue and its relatives, except to say I used it once and will never use it again. I have heard enough stories about fish glue failure to satisfy my curiosity.
The above list comprises all the experience I have with glues. Polyvinyls, fish glue, and Gorilla glue have no place in my shop. I have not used epoxy in years, but I may use it again. The failed headstock repair in the other thread is a definite candidate for epoxy. I try to keep all the others in stock in my shop. I date the containers when I buy them, and generally discard them after a year, except for the cements.
Anybody else care to chime in on what they are positive as being reliable glues for our craft?
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