Hide glue: gram strength how to measure?

[Bart van Weperen]

Hi all,

 

Finaly I found a supplier for Hide Glue! But: there is no info at all on it's gram strength and my asking for that info was answered with a "what is gram strength? Hide glue is hide glue, I didn't know there were differences"... (The other suppliers didn't even bother to answer my question)

 

So I am in the process of trying to find out what gram strength "my" glue has. In the end I want to know if this is or is not usable for my guitar-project(s).

 

I mixed the granulates in 6 different ways: (granulates to water) 1:1, 1:1.5, 1:1.9 (Franks mix), 1:2, 1:2.5 and finaly 1:3.

 

The 1:1 hot glue (60 degrees Celcius) runs off a teaspoon same as syrup: the 1:1.5 mix is already starting to be too thin, it runs off the spoon as yoghurt. The 1.9 and higher mixes are (as I see it) not usable. They look like water (Or in this case: tea with milk, only the smell is different).

But: all the tests with all these mixes, clamped for only an hour and a half, not only stick but I cannot take them appart with my bare hands... The more I experiment, the more I'm "flabbergasted". The runout of the 1:1 is hard, the runout of the 1:2 (and higher) is still hasn'n hardened (but the joint sticks!???)

 

On Frets.com Frank wrote that the higher the gram strength of the glue, the more water is needed to get the right consistancy... So I take my glue to be of lesser gram strength than the 192 that Frank is using. (mixed 1:1.9 his glue just starts to drip off his brush, mine is almost as water in that mix).

He also writes: "Glue is graded on a basis of its gel strength, a measure of how many grams of force it requires to depress a 1/2” plunger 4mm. into a 12.5% protein solution of the glue at 10° C." I do not understand the "12.5% protein solution of the glue". Does that mean I should take some usable (already mixed) glue and make a solution with that (12.5% glue, the rest water)?

 

Should I worry at all about the gram strength, or am I chasing ghosts?

The final question is: how can I make sure this HIde glue is good enough for what I want to do with it. Can be that you will answer: just use it and see if it holds with time, but also that answer will help!

 

Thanks in advance for your answer(s)!

 

[Frank Ford]

My measurement of 1:1.9 is by WEIGHT, so if yours is the same then it probably is a low gram glue. 1:1 by VOLUME is about right for the 192 gram glue. Don't forget that these are general guidelines - you can always make up and test some of your glue to see how it performs.

[Bart van Weperen]

I'm sorry Frank,

I forgot to mention that I mixed by weight... (Learned that from frets.com)
As my test-joints are still holding, I think I have an OK batch of hide glue.

Thanks for your reply!

[Greg Mirken]

I think we tend to over-intellectualize hide glue. After all, once the water has evaporated from a joint the stuff that remains is the same. At one extreme, you don't want to end up with a starved joint; on the other hand if your mix is too thick you'll have too thick a glue line with reasonable clamping force. But there's a wide range of mixtures that will produce a fine joint with no difference in strength. I like my glue about the consistency of milk; I have enough working time before it starts to gel. As it sits in its water bath during an afternoon, I might add a little water several times to keep it at the consistency I'm used to. If I screw up and get it too thin, I find something else to do for awhile.

My understanding is "gram strength" (or gel strength, same thing) tells you more about the working properties of the glue than the strength of a joint.

[Bart van Weperen]

Hi Greg!

I think you're right with the "over-intellectualizing"... I stop bothering about gram strength and start using my glue, after all the test joints hold... Only possible conclusion: this glue does what it's supposed to do.
I find it amazing that even the verry thinned mix has the strength that it has. Now I understand why it is such a good material for repairing cracks!

Thanks!

[Ned Knepp]

Since most of my hide glue needs are for repairs, a small plastic cup ( like Frank mentions on his site) is usually enough. I measure out my glue and water into the little plastic cups on a postage scale. I'm actually not too worried about the ratio so much as I know that I will waste a LOT of glue if I don't measure it out. I usually use a 1:1.5 ( or there about) ratio of glue to water by weight but once it's set around in the pot for a while it won't be nearly that. Like Greg, I don't hesitate to thin it over time with more water if it is a bit thick when I want to use it and so far it has always held for me.

When I first started using hide glue, I was really worried about getting the consistency just right and I felt like I had to have everything setup to go when my glue was ready so it didn't loose too much moisture. Finally, I realized that no matter how thick or thin the glue was, just a little bit on my fingers was guaranteed to stick to everything I touched until I got it ALL off of my fingers. That's when I realized that this glue wasn't as demanding as I thought. To me getting things in place and clamped up in short order is much more important than getting the mixture and consistency exactly right. If I have a complex clamp-up, I don't hesitate to thin it out a bit more that I usually like it to buy a bit more time.
Ned

[Bart van Weperen]

Hi Ned!

I feel I finaly get the hang of it... Even verry thinned-down hide glue does the job.
At first I realy believed that the amount of water added to the granulates had a big influence on the glue strength... My mistake: it only makes the glue more or less liquid, and therefore usable for different applications.
Thanks for helping me understand!

[Pierre-Antoine Roiron]

Until a certain amount of water, I think that's right too.

[Ned Knepp]

Pierre makes a good point. I'm fairly sure that too much water will create a weak bond. What I make has a certain consistency, not too thick that it's already Gel but I like to have a bit of a "coat" when I apply it. I don't think it is quit as thin as milk, as Greg likes, but I think this may be personal preference and I doubt there would be much difference if you got our glue together.

It's that consistency that I have developed a feel for and if I have to add a bit of water to get it, I do. There have been a few times that I felt that I over did the water and I let it set for a while but I haven't done that for a long time now.

I honestly think that the water content has an effect on the glue bonds holding power but I haven't seen that it effects me in practical usage. As long as I stick to my process, the glue holds up.

Ned

[Howard Klepper]

It almost certainly is more than good enough. Best way to test gram strength is ask the manufacturer.

[Bart van Weperen]

Hi Pierre-Antoine, Ned and Howard!

Sure, too much water will lessen the glue strength and will make for failing joints, I agree. While testing "my" different mixes I was convinced that the 1:3 mix was sure to fail... I dripped some drops of this tea-like glue on a small piece of wood, tipped that piece and I saw this glue running off as if it were water. Also that joint still holds...
I don't intend to try to find out the "failing point", but there will be one, I'm sure! I Guess I will find out unintentionally in the end anyway :-(

By now I think "my" glue is good, no doubt left.

And yes, Howard: the manufacturer would be the one to ask for additional info... Too bad that the can arrived without any label!
But hey: I just want to learn how to build and repair guitars... I Think I just let them have their little secret!

Thanks for your input!
Bart