Hide glue for grain filler? Serious stuff

thewizardofaz

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Hey Les Paul master builders, I got some questions.

I woke up with some thinks that had been buzzing around in my head all night. I like to think outside the box, so to speak, when the subject of guitar finishing comes up. The use of hide glue as the grain filler is one of these. To my mind, guitars and the materials used: woods, wire type, pots, strings, tuner material and mass, pickups, switches, etc. form a "sonic ecosystem". Change one variable and you change the end product, sound, maybe significantly, maybe subtly.

Fully cured hide glue is a very, very, thin and crystalline material. Crystals allow sound to pass through them more freely, more uncolored, and more cleanly from one point in the body or neck to another than traditional paste grain filler or glue just because of what they are. It's like asking, "does your foot go into a pool of water or a a thick pool of mud faster?" Hide glue goes from a liquid to a crystalline form, titebond type glues get thinner when you clamp them, but essentially they stay liquid. I'm really interested on this and how it effects sound passing through neck and body surfaces.

We know hide glue neck joints are stronger and do not drift. Well, some of us believe this. As hide glue gets thinner and draws the parts tighter, water evaporates or is absorbed and it crystalizes. The parts are now tighter fitting and much less insulated from each other than when a layer of titebond type glue is used. Tightbond glues never harden. They are always in a "liquid" or plastic state. Titebond type glue joints never fully harden and can shift. Sound is muted when it passes through a plastic (like that truss rod condom). I love it when a neck vibrates like crazy in my hand, as if I'd inserted a quarter in some imaginary slot.

Paste filler's composition is denser and insulating. When sound is transmitted through it, sounds are naturally muted and slowed down when compared to hide glue. It might be like listening to a conversation through a glass window and then hearing the same conversation through plastic, such as plexiglass. A plexiglass canopy of an aircraft is very sound insulating. We can say sound clarity varies with the material it's being transmitted through.

The sound passing through a neck which is traditionally grain filled has a cross path fading effect as a result, much like the same effect on transmitted radio waves. A transmitted radio signal takes two (actually many) paths before you hear it: down to and along the ground to the receiver (which is the same as a sound from the vibrating string, down through the pickup to the body, wiring and neck wood) and a signal (string vibration) which passes in a line of sight directly from transmitter (string) to receiver (pickup). On a guitar, you are in no small part, substituting wood for the medium through which the sound (or radio wave) is transmitted and a vibrating string producing it. (I'm an old SIGINT spook who used various radio receivers extensively when I was in the Air Force 25 years. I know this effect quite well). I think we can make an assumption that radio waves and audible sound waves are essentially the same things, they're just in different frequency bands, but behave essentially the same. An omnidirectional transmitted radio wave (string vibration's sound) takes many paths: the two we're interested in are the direct line of site wave (the string vibration) and ground wave (the sound picked up from the contact of the pickup to the body wood). A radio (vibrating string) has signals emitting from it into the atmosphere and directly down to the receiver (the pickup). At the receiving end (the pickup), two (actually more) signals are picked up. The first directly from string to pickup and the second from string to the pickup, through the body and neck, and back to the pickup again. These combine. These sounds are received chronologically different times. String to pickup sounds first, followed later by wood to pickup sounds. Wood to pickup vibrations are weaker and will be colored, depending on what kind and how much wood and in our case, grain filler, they pass through. These signals come in to the pickup (receiver) at varying amplitude and bandwidths. When this happens, the signal or sound that comes out of the speaker can be distorted or sonically changed. Sometimes there is even a kind of reverb effect to the sound which is not there if the signals are listened to individually instead of combined. That's why some early reverb "machines" were merely sounds bouncing around inside a large tank. This same situation occurs in much the same way with sound vibrations in a guitar body.

I believe hide glue should be superior to titebond glues or grain filler, not only for joints, but also when on wood surfaces instead of a grain filler. There's less vibration diffusion, less slowdown of the vibrations gong from the body up through the neck via the strings, to the tuners and back down the neck again into the cavities where the pickups will receive the sound again due to their body mounting. Plasticized grain filler vibrations slows down the passage of vibrations, diffuses them, mutes and weakens sound as it goes through the neck or body. Even though grain filler is just on the surface part of the "sonic ecosystem" the effects will be significant less pleasing compared to hide glue. Acoustic guitars using only hide glue sound different and some would say better than those using titebond type adhesives.

A concern I have though, is that since hide glue is 2/3 water, its application to the back of a neck may induce a light to significant bowing of the neck, either up or back. This then begs the question, will the truss rod be able to compensate, or will the neck, when the moisture is completely gone, resettle and be fine?

I'm going to double post this over on the lespaulforum and the mylespaul forum and see if I can get some serious feedback.
 

bfcg

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Hide glue as a wood filler was very common long ago and not so long ago. Many of the finest stringed instruments over the past centuries were grain filled with animal hide glue.
I think with the advent of high tech, faster curing and less shrinking stuff, hide glue as a filler got left behind.
Some crappier companies are using epoxy as filler for production speed.
 

bfcg

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Even though hide glue is not always 2/3 water, I would not advise using it on the neck.
Different viscocities for different strength and uses.
The radio wave analogy that you used is slightly different than the mechanical or kenetic energy that produces and audible tone. The radio waves are not compressing and refracting air caused by mechanical vibration. Only after the electrical signal is amplified , sent to a transducer(voice coil in speaker) to be converted to mechanical energy and then the speaker cone that creates the air pressure will you hear it.
But I do agree with the sound being more pure with fewest "dampers".
 

57special

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Can't speak to how much hide glue will improve tone, but it is very easy to use as a grain filler. Just used it as a filler for the first time last night (I've used it for years on joints). Wouldn't worry about the amount of water bowing the neck, as very little glue is left on when you use it as a filler by;

- brushing on wet
- wiping or scraping off when rubbery(20 minutes or so)


far more water is introduced to the neck when hide glue is sued to join the fingerboard to neck.
 

dschwartz

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That's a lot of analythic thinking youre having about something that can be proven scientifically..

But your train of thought is mostly based on inductive theories based on analogies and projections of behavior..

For example, comparing a 0.00001" thick layer of sealer with a glass window, sounds off to me..maybe if youre comparing playing a guitar behind a window or whithout the window, the logic would make sense to me..

I agree that part of the tone is a mix between the resonance of the body and the actual string picked up, but i dont think something as minimal as the type of sealer would make any difference..

The worst thing is that it cant be proven scientifically unless you use two Identical pieces of wood..and that doesnt exist..and is the most sensible part of good resonance..
 

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