Double Bass classroom repair - epoxy vs wood glue?

[groooooove]

I have two cellos in my classroom that need repairs... one had the scroll broken off, the other the neck broke off near the heel.

both are clear breaks and should clamp up easily. both are cheap Chinese instruments not worth paying anyone else to work on.

for the sake of resting assured that these repairs are as strong as possible; would you use 2 part epoxy, or titebond wood glue?

I was planning on using the wood glue, but figured it would not hurt to ask.

 

[Steven Ayres]

Definitely not the epoxy. The Titebond might be OK for the scroll if you can't see another future repair. On the neck repair I think we'll want to see the situation in more detail.

 

[groooooove]

Definitely not the epoxy. The Titebond might be OK for the scroll if you can't see another future repair. On the neck repair I think we'll want to see the situation in more detail.

I can snap a few photos tomorrow

the broken off neck is right at the heel, the "normal" spot where 10 year old cellist tend to break necks...

any reason why "definitely not" epoxy? is it not going to hold? Or is titebond just going to hold better?

And again, these are cheap instruments and i only need these repairs to last another 2-3 years, then I should have the budget for new ones.

 

[Steven Ayres]

any reason why "definitely not" epoxy? is it not going to hold? Or is titebond just going to hold better?

This instrument will outlive you if maintained right, and you want to be able to redo a repair that goes wrong, and allow for future repairs. Both epoxy and PVA are polymers that cure harder than the wood and are impossible to remove without damage. Epoxy doesn't really bond with wood and requires more space than you want in any wood repair. PVA soaks further into the wood, but hide glue (the right stuff) won't stick to it if it's in the fibers.

Luthiers use PVA sometimes for crack repairs that aren't likely to see another repair, but it's not a favorite. It's usually more practical to use than hot hide glue for most people, I'll grant, but it's setting up a future problem if not handled right.

Neck repairs involve more serious engineering concerns, and just gluing it back together probably won't work under tension; using PVA for that will lead to a more complicated repair or replacement later to get it right.

 

[groooooove]

This instrument will outlive you if maintained right, and you want to be able to redo a repair that goes wrong, and allow for future repairs. Both epoxy and PVA are polymers that cure harder than the wood and are impossible to remove without damage. Epoxy doesn't really bond with wood and requires more space than you want in any wood repair. PVA soaks further into the wood, but hide glue (the right stuff) won't stick to it if it's in the fibers.

Luthiers use PVA sometimes for crack repairs that aren't likely to see another repair, but it's not a favorite. It's usually more practical to use than hot hide glue for most people, I'll grant, but it's setting up a future problem if not handled right.

Neck repairs involve more serious engineering concerns, and just gluing it back together probably won't work under tension; using PVA for that will lead to a more complicated repair or replacement later to get it right.

I completely understand that under normal situations, we "do no harm" and use the correct glue so that the instrument will be used long after I am gone. These instruments are definitely not lasting for generations, they're cheap chinese cellos that have been trouble since they were new and have only gotten worse. I can't stress "cheap chinese garbage" enough

so, in this situation (hot hide glue is not an option) - is wood glue the lesser of the two evils in general? definitely easier to work with in a classroom, so that's fine for me.

 

[Steven Ayres]

is wood glue the lesser of the two evils in general? definitely easier to work with in a classroom, so that's fine for me.

PVE is more likely to work as you imagine on no-stress repairs, but I'll repeat that it's pretty likely it won't work for the neck repair as you imagine. Neither is evil, both are simply inadequate tools for what you want to do. If you just want to do an experiment and can afford to throw the instrument away when it fails again, live it up. But if you're doing this because you want the instrument to make music, its build quality is really immaterial to the problem. We're talking practical engineering, not museum conservation.

 

[DoubleMIDI]

What is the reason you cannot work with hot hide glue?
If you don't know how to get them use gelatin (sheet like used in the kitchen) which is basically the same as a bass builder told me.
If you cannot make the repair at school take them home for a few days to do it there. At least one of them is unplayable now, so it doesn't matter where it is unplayable.

If you never worked with hide glue, I would try the scroll first, since there is much less stress on it. The only thing you have to check before applying the glue is how to fix it for a longer time under some pressure since the closer the wood grains the better the hold.
Don't forget that it is hot hide glue and everything is reversible and removable. If you successfully glued the scroll you can try the neck.

I don't recommend the following for a cello (not enough wood at the neck) but I once got a neck repair from a woodworker (luthiers my parents tried at that time refused to work on the instrument due to the value of it) by glueing the neck on (probably with some kind of PVA) and screwing through the fingerboard into the heel with one big screw and sealing the top with black wax. Did hold for many years until my bass was stolen. But I wouldn't do that to a cello.
Removing the fingerboard first to make the screw invisible under the fingerboard might no leave enough wood in the upper part (depending on the break) and you need to reglue the fingerboard then (preferably with hot hide glue, since you might need to retight the screw later).

 

[groooooove]

PVE is more likely to work as you imagine on no-stress repairs, but I'll repeat that it's pretty likely it won't work for the neck repair as you imagine. Neither is evil, both are simply inadequate tools for what you want to do. If you just want to do an experiment and can afford to throw the instrument away when it fails again, live it up. But if you're doing this because you want the instrument to make music, its build quality is really immaterial to the problem. We're talking practical engineering, not museum conservation.

Glad I asked..

I have definitely seen countless student cellos with this repair, often in a sloppy epoxy job. I have at least one cello that this was done to in the past and it's been fine for years...

would hot hide glue be more stable and stronger in this application? I wonder if any school approved vendors sell the gear to have it ready for next year...

 

[groooooove]

 

[210superair]

I'm currently repairing a break exact like that on an old Kay cello. The guys on here have been awesome helping me do it. You may want to check it out, a few good things in there, and mistakes I made that may make it easier on you. I'd also check out Steven Ayer's Kay Jazz cello thread, lots of useful info in there.

I second the hide glue. It's not that difficult to work with at all, and you'll know it was done right!

Neck heel cello repair, wish me luck

 

[dramatwist]

I completely understand that under normal situations, we "do no harm" and use the correct glue so that the instrument will be used long after I am gone. These instruments are definitely not lasting for generations, they're cheap chinese cellos that have been trouble since they were new and have only gotten worse. I can't stress "cheap chinese garbage" enough

so, in this situation (hot hide glue is not an option) - is wood glue the lesser of the two evils in general? definitely easier to work with in a classroom, so that's fine for me.

...might want to re-think this... instruments made in China, for the most part, are quite good... they were making musical instruments before the USA was the USA... "cheap Chinese garbage" is no longer valid...

 

[Fredrik E. Nilsen]

"cheap Chinese garbage" is no longer valid...

As a generalisation, it's not valid. But still, there's a lot of chinese garbage coming out. More so than from most other countries atm.

 

[groooooove]

...might want to re-think this... instruments made in China, for the most part, are quite good... they were making musical instruments before the USA was the USA... "cheap Chinese garbage" is no longer valid...

I'm well aware! I'm a big fan of shens, snow, and similar quality instruments made there.

These particular instruments are really of the lowest quality.

As pictured, i went ahead and used wood glue on that scroll. I think it will hold. maybe not.

unsure what to do about the neck... as is I only have enough claps to do one at a time so I have a day to think about it!

Thanks for the insight folks.

Will see if my admins approve hot hide glue materials for next year...

 

[1st Bass]

If your budget is the issue:
My glue-pot set-up is a potpourri warmer I acquired at a Goodwill store for $3, with an old, empty yeast jar as the actual glue container, sitting in the water bath of the Potpourri warmer. A natural fiber artists paintbrush is my "glue-brush." I have used this set-up for nearly 20 years, and have replaced the yeast jar once, because the lid rusted out, and the brush has been replaced two or three times...they eventually start losing hairs.

The hide glue granules are quite cheap, available from International Violin Co. online, or, as someone mentioned, you can buy the dry gelatine at a grocery store, and it will work fine.

So you are talking about an investment of right about $10, more than likely... Some have used a second-hand baby-bottle-warmer...same idea.

Hide glue is phenomenally strong, and completely reversible. As someone else mentioned; properly repaired, the instrument will outlast you... why not do it right?

 

[Don Hergert]

... you can buy the dry gelatine at a grocery store ...

Just to clarify this for the OP and me and anyone else who is interested, what should a person look for in the grocery store for this product? Is there a preferred brand name, or something similar to ask about at the store?

Also, I'm guessing this is mixed with water only? Is there something else that should be mixed with it? Lastly, how do you judge when it is thick enough for the neck repair in question?

Sorry for all the questions, but inquiring minds... Personally, I have no repairs to do immediately but would really like to know how to work hot hide glue if needed for a properly glued repair in a hurry (ie: grocery store sourced), such as for an emergency guitar peghead break repair at a festival, etc. Thanks!

 

[Steven Ayres]

Yeah, the neck break is pretty close to the front, and adhesive alone will be iffy. HHG is the better bet here because it allows much closer mating of the separated fibers. You have to be precise with it, though, and work really clean.

Best practice on this is probably more work than you can afford to put into it, and I expect you're doing this in your free time because there's no funding for repairs. The district decided to go cheap, and it's unreasonable to push the inevitable costs of that decision onto you. It seems to me that what will solve the problem for the students most efficiently would likely be a new (better, donated) Chinese cello-shaped object.

 

[1st Bass]

I have used "Knox" gelatine...used for canning purposes, and comes in granule form, but I understand there are other brands, some of which come in sheet form.

Using granules, I put, say, a tablespoon of the granules into my container, then add enough cold water to cover the granules, and let it sit until all the water has been absorbed.

Then heat it (no more than 145 deg. Fahrenheit) until the glue melts. It should be a syrup consistency, in my experience. Some want it more like honey, but I find that a little difficult to deal with, and sometimes have ended up with a thicker glue-line than I wanted. You can add water to thin it.

If it sits open, it will "skin-over", so it is best to cover it when you are not actually working with it, so the surface does not dry out. If you cover it promptly when you are finished, so that mold spores can't get in, it can last for a long time in the jar. Storing the covered glue in a refrigerator will also add to the longevity.

 

[Don Hergert]

Thank you!!!

 

[DoubleMIDI]

I don't think HHG is working for a festival gig on the same day, specially if it is a broken neck or pegbox or something similar where there is a a lot of tension involved. I think it might work best if it dries overnight.
But what do I know about that ...

 

[1st Bass]

I give it overnight for most repairs. When it is a broken neck, I agree with Steven...I think it needs some reinforcement, but there are many luthiers who disagree. Perhaps it would be smart to remove the fingerboard and add a dowel...but maybe not.

But Hide glue sets up in two phases: first, it gels, and becomes pretty solid. Then, as it actually dries, it shrinks and pulls even tighter. I remember a friend making "obscure" glass by painting very thick, hot hide glue onto heavy plate glass, then slipping the whole mess into a big padded envelope. As the glue dried, you could hear the "Ping! Pinnng!" as the surface of the glass was literally being pulled off by the shrinking glue. The end result looked very much like the surface of a hand-flaked arrowhead. Pretty impressive.