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Andreas Preuss

Can gorilla glue hold a broken bow head?

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Just now, David Burgess said:

Uhm, you might want to take another look at that.

Please explain.  :huh:

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2 minutes ago, Violadamore said:

Please explain.  :huh:

Lots of hide glue gelling retarders have been around for a long time. Most of these (though I have by no means tested them all) make the dried glue much more hygrosopic, more susceptible to reliquification, and more subject to creep.

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1 minute ago, David Burgess said:

Lots of hide glue gelling retarders have been around for a long time. Most of these (though I have by no means tested them all) make the dried glue much more hygrosopic, more susceptible to reliquification, and more subject to creep.

OK.  Thanks.  I wasn't considering anything before Titebond.   Crap!!!  :rolleyes:

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8 hours ago, David Burgess said:

Lots of hide glue gelling retarders have been around for a long time. Most of these (though I have by no means tested them all) make the dried glue much more hygrosopic, more susceptible to reliquification, and more subject to creep.

I've read in older writings about use of common table salt as retarder. I believe some even recommended it just to prevent your glue from going bad when left in the pot for a few days.

I wonder why CA is not considered for bow frogs. It glues ebony very well and is water resistant. In need can be removed using acetone.

 

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22 hours ago, fiddlecollector said:

The alternative is called N-acetyl- L glutamine, in powder form often used by health freak/body builder types and i bought 100gms of pure powder of amazon for around £7,which will last me years.

I did various tests on pieces of ebony and all were successful as far as im concerned.

You add 2-5% of the powder to the dry weight of the hide glue.Then make the glue as usual.

I wonder if it changes some properties of the HHG like cold creep? Is the thin glue foil as brittle as clear HHG? Another quastion is whether HHG will hold well on surfaces contaminated with the N-acetyl- L glutamine treted glue (as in repair of broken centerjoint)?

I have one direct experience with HHG joints exposed to extreme conditions - when I was disassembling old firewood shed at our weekend house some of the siding boards were originally parts of old furniture certainly jointed with HHG (they were pre - WW2) and they were exposed on southern side - hot sun in summer, water and snow etc. Upper parts that were covered from direct rain and snow were still holding together, only the parts that were touching gound became unglued. Of course there was no constant tension of strings, but changing weather can cause quite a tension as well.

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I have realised that i dont know how this stuff works ,just that it does .

I have found excerpts from one of the articles i read and realised i bought the wrong stuff(N-Acetyl -L Glutamine). Unless Amazon sent me the wrong stuff because they sound similar and i didnt realise :angry:Considering im a former chemist im quite embarassed . I will still use it. But will also try the correct stuff which is N-acetyl-D Glucosamine.

The proper stuff N-Acetyl -D Glucosamine which is a sugar complex, apparently works partly by the Maillard reaction crosslinking with the gelatin. Also the longer you can keep the joint at an elevated temperature the stronger the joint. The tensile strength of the modified glue can increase to up to 170 - 200+MPa. Whereas unmodified  hide glue is a maximum of around 40 - 70 MPa.  So that a huge increase. So creep using N-acetyl-D Glucosamine  modified hide glue ,would be likely less.Just guessing here .

A few other things, some use glutaraldehyde instead of formaldehyde for cross linking. Apparently this only has a surface effect on gelatin ,so it will not be as water reistant as when using N-Acetyl-D Glucosamine.

Most types of sugars such as sucrose ,glucose,etc... also crosslink gelatin. Heating of the joints of over 50 centigrade for a few hours increases tensile strength and water resistance- this applies to all sugar types .

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43 minutes ago, fiddlecollector said:

I have realised that i dont know how this stuff works ,just that it does .

I have found excerpts from one of the articles i read and realised i bought the wrong stuff(N-Acetyl -L Glutamine). Unless Amazon sent me the wrong stuff because they sound similar and i didnt realise :angry:Considering im a former chemist im quite embarassed . I will still use it. But will also try the correct stuff which is N-acetyl-D Glucosamine.

The proper stuff N-Acetyl -D Glucosamine which is a sugar complex, apparently works partly by the Maillard reaction crosslinking with the gelatin. Also the longer you can keep the joint at an elevated temperature the stronger the joint. The tensile strength of the modified glue can increase to up to 170 - 200+MPa. Whereas unmodified  hide glue is a maximum of around 40 - 70 MPa.  So that a huge increase. So creep using N-acetyl-D Glucosamine  modified hide glue ,would be likely less.Just guessing here .

A few other things, some use glutaraldehyde instead of formaldehyde for cross linking. Apparently this only has a surface effect on gelatin ,so it will not be as water reistant as when using N-Acetyl-D Glucosamine.

Most types of sugars such as sucrose ,glucose,etc... also crosslink gelatin. Heating of the joints of over 50 centigrade for a few hours increases tensile strength and water resistance- this applies to all sugar types .

Does this mean that normal sugar added to the glue will strengthen the joint?

(you wrote 'most sugars' and at the end of the sentence 'all sugar types', so what is correct 'all' or 'most'?)

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It should yes ,improves with heating the joint . Also water resistance improves.

Heres a graph/chart showing efect on water reistance after 90 days in water.

It shows straight gelatin/glue, sucrose (common white table sugar), glucose, glucosamine and finally the best N-Acetyl-D Glucosamine. So sort of  disproves slightly the idea that adding sugar attracts moisture.Dont know if honey works but probably soewhere between glucose and sucrose.. Notice though that N-Acetyl-D Glucosamine has a huge effect compared to other sugars.

water resistamce of sugars crosslining gelatin.JPG

 

Heres a similar one for effect on tensile stress.

 

sugars tensile stress.JPG

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Hi Andreas,

I have no confidence in cyanoacrylate or epoxy for these kind of joints but was once asked by a favorite client to glue a cello neck on a cheap student's cello which had broken at the usual spot due to a fall.

 I used gorilla glue from the hardware store and was extremely impressed. I followed the directions which included wetting the joint surfaces first and then applying a very thin layer of glue before clamping. The result was a joint which was totally invisible under minor retouching and as far as I know has been holding for about five years with no problems whatsoever. That is my only experience with it but for what it's worth...... 

I would wonder if the oily nature of pernambuco might make it work differently.

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I have also used Gorilla Glue to glue the broken necks of cheap cellos that otherwise would have been fire wood.  They have all held as far as I know.  I have never used this glue on bows or on anything else, nor do I intend to.

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The bow repair staff in one of the shops where I worked previously used G2 for splines, frog repairs, handle cracks, and fill. The results were impressive and I didn’t see any failures. However, a well-known specialist in splines later showed me that he could also get excellent results with CA glue for the same repairs, with the benefit that everything could be undone with acetone fairly easily. I also know of several bows glued with CA and not splined that have held for years.

I’m intrigued by the experiments with additives to hide glue but have yet to try it.

As far as the question of whether to spline or simply glue, I think context is key. For an expensive bow that is used regularly by a professional player, there is much more pressure to make a repair that is absolutely solid. If a repair fails, especially on stage, it can seriously damage the credibility of a repairman’s work. Viewing it from this perspective, there’s an argument to be made that even if the glue might be strong enough, the spline is an extra line of defense.

In the case of a bow that is not as valuable or isn’t being relied upon as much, it’s safer to try repairs that are less invasive, knowing that there’s some chance of failure. In that situation, the customer is more comfortable with a bit of risk and might not be as concerned if the repair doesn’t hold and must be redone.

The strength of modern glues like marine epoxy and CA is impressive. It’s just difficult to determine absolutely whether those glues are strong enough by themselves. I’ve seen glue joints that failed and spines that failed as well. Even if the glue is strong enough, sometimes it all comes down to the preparation and skill of execution. 

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It works, or you can buy a dedicated CA solvent (which has additional ingredients to soften the CA).  I have used several brands, and currently use  FastCap 2P•10 Debonder, which works very well.

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13 hours ago, nathan slobodkin said:

Hi Andreas,

I have no confidence in cyanoacrylate or epoxy for these kind of joints but was once asked by a favorite client to glue a cello neck on a cheap student's cello which had broken at the usual spot due to a fall.

 I used gorilla glue from the hardware store and was extremely impressed. I followed the directions which included wetting the joint surfaces first and then applying a very thin layer of glue before clamping. The result was a joint which was totally invisible under minor retouching and as far as I know has been holding for about five years with no problems whatsoever. That is my only experience with it but for what it's worth...... 

I would wonder if the oily nature of pernambuco might make it work differently.

Hi Nathan,

i wonder how it came that you were able.to make the joint with gorilla glue invisible because the glue expands. Must be your genius. ;)

never tried gorilla glue on broken cello necks, but I have one half size sitting around which was given to me.

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7 minutes ago, Strad O Various Jr. said:

If you glue something with gorilla glue and it fails there's not much you can do, whereas with hide glue, which is just as strong, you can clean up with hot water and do it over.

If you refer to necks broken at the heel, hide glue is simply not strong enough. 

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54 minutes ago, Strad O Various Jr. said:

neither is gorilla glue, hide glue is strong enough if it is reinforced

You mean with chemicals quoted by fiddlecollector? 

(Then I would prefer if you'd use the term 'reinforced hide glue' to avoid confusion.)

Anyway, do you have experience with washing out reinforced hide glue? 

I am asking because some chemicals make hide glue insoluble in water once it is dry.

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20 hours ago, Strad O Various Jr. said:

I hear people claiming CA glue can be undone with Acetone, has anyone actually tried this to see if it works??

Yes. You can make a pond of acetone and soak the part in it for several hours. I know someone who has a couple shot glasses set aside just for ponding frogs or stick handles to remove old glue.

In bow restorations, the first step is often to clean out all the old glue in order to determine how the damaged area will fit together when glued properly.

I’ve used acetone to release CA glue from slides on cheap bows. For some reason some factories put a bit of CA on the frog under the rear of the slide. In cases like that, acetone is often the only thing that seems to release the slide.

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For all those who are interested, I jumped without parachute and glued the head. Of course I tried to break it off with the force of my hands afterwards and it was holding. With hairs tied up pretty much it was holding. 

But one never knows. I gave the customer a trial period of one month. If it breaks no payment. He walked out of the store with a happy face.

 

image.jpeg

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1 hour ago, Andreas Preuss said:

For all those who are interested, I jumped without parachute and glued the head. Of course I tried to break it off with the force of my hands afterwards and it was holding. With hairs tied up pretty much it was holding. 

But one never knows. I gave the customer a trial period of one month. If it breaks no payment. He walked out of the store with a happy face.

 

image.jpeg

GoodJob.gif.97732e73ac60e13f043b392080da68c5.gif

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2 hours ago, Andreas Preuss said:

For all those who are interested, I jumped without parachute and glued the head. Of course I tried to break it off with the force of my hands afterwards and it was holding. With hairs tied up pretty much it was holding. 

But one never knows. I gave the customer a trial period of one month. If it breaks no payment. He walked out of the store with a happy face.

 

image.jpeg

It certainly looks good. Time will tell the rest of the story.

What glue did you end up using?

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On September 12, 2020 at 5:08 AM, Andreas Preuss said:

Hi Nathan,

i wonder how it came that you were able.to make the joint with gorilla glue invisible because the glue expands. Must be your genius. ;)

never tried gorilla glue on broken cello necks, but I have one half size sitting around which was given to me.

I was surprised as well but I think using a very thin application of glue and firm clamping is the answer. 

Looks like you also were able to get a very tight glue line.

Nice job

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