finishing inside the guitar (Full Version)

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etta -> finishing inside the guitar (Dec. 1 2011 20:09:11)

This has probably been discussed, but why do some builders finish the insides of their guitars? I have three at the present, very nice instruments, that have finish inside.



Gimar Yestra -> RE: finishing inside the guitar (Dec. 1 2011 21:56:03)

so the inside of the guitar can't absorb moisture as easily compared to unfinished wood.

there are also theories about how a finished interior can change the reflection of sound, I haven't experimented with that theory so can't say much about it.



Stephen Eden -> RE: finishing inside the guitar (Dec. 2 2011 18:02:36)

yup thats usually it to stop moisture. Another reason could be to stiffen the wood up a bit more! Its a pain if you need to do a repair by adding a cleat cause you have to sand the finished off th inside before you can glue. Not easy if you have larger arms!



Anders Eliasson -> RE: finishing inside the guitar (Dec. 2 2011 19:31:15)

So a question:

Is this one more of these hypothetical issues or is there something usefull about it.

One of my guitars has survided many years in Taiwan where humidity is VERY high. Its not finished on the inside.



Sean -> RE: finishing inside the guitar (Dec. 2 2011 20:05:20)

I blame Brazilian Rosewood[:-]



estebanana -> RE: finishing inside the guitar (Dec. 2 2011 22:08:32)

Finishing the inside does not stop humid conditions from changing the guitar or making it expand and contract do to humidity changes. The guitar will still change, but a tiny bit slower.
IMO finishing the inside is really stupid.



Stephen Eden -> RE: finishing inside the guitar (Dec. 3 2011 10:06:33)

Hehe yeah, to me it does seem a bit like clutching at straws to find that magic ingredient or Gimick so to speak.



Anders Eliasson -> RE: finishing inside the guitar (Dec. 3 2011 10:10:17)

or just another way of selling guitars



etta -> RE: finishing inside the guitar (Dec. 3 2011 15:15:23)

In addition to my question about finish, I might add that the two best sounding guitars I have played are a i959 Hernandez y Aguado, blanca and a recent Glenn Canin Brazilian, both finished inside. I cannot say if the finish has any effect on the sound. Thanks for your observations.



CMND/CNTRL -> RE: finishing inside the guitar (Dec. 6 2011 8:56:47)

I don't see anything gimmicky about it. It looks damn sexy if you ask me. I'll be in the market for a custom order soon and will be requesting at least a finished inner back. I don't see a reason not to have it finished aside from some extra labor. I think it makes guitars look cleaner.



Andy Culpepper -> RE: finishing inside the guitar (Dec. 6 2011 13:02:23)

There is a certain amount of damping that occurs when you finish the outside of the guitar.. I personally believe it's a good thing because it focuses the sound and quiets down some of the extra "noise" of the guitar. BUT I'm really not sure I want to potentially multiply that effect by finishing the inside too. I do think the wood needs to "breathe" to some extent, I think that's part of the aging/breaking in process that really brings out the voice of a guitar.



etta -> RE: finishing inside the guitar (Dec. 6 2011 18:01:40)

Andy; your points about finish seem to make a lot of sense to me. However the Brazilian G. Canin I play (no port) projects better than any guitar I have heard. Could the finish add a reflective/projection effect to the sound?



TANúñez -> RE: finishing inside the guitar (Dec. 6 2011 18:59:05)

quote:

I do think the wood needs to "breathe" to some extent, I think that's part of the aging/breaking in process that really brings out the voice of a guitar.


Totally agree with this. I think finishing the inside would slow this process down. I do however, from time to time, finish the back reinforcement strip and back braces but never the inside of the back and sides.



Sean -> RE: finishing inside the guitar (Dec. 6 2011 19:43:00)

Other then an attempt at helping prevent Brazilian Rosewood from cracking I don't see the point. Take Walnut for example, it has a warmth to the touch about it, covering that up with a hard cold finish would just be character assassination



estebanana -> [Deleted] (Dec. 6 2011 20:50:53)

Post has been moved to the Recycle Bin at Dec. 6 2011 21:10:16



TANúñez -> RE: finishing inside the guitar (Dec. 6 2011 21:58:51)

There has to be a reason more makers don't do it than those that do. Even high end steel strings. Both my Martin and Taylor are left unfinished inside.

I once saw a flamenco guitar with the entire inside finished in black lacquer. [:'(]



HemeolaMan -> RE: finishing inside the guitar (Dec. 7 2011 3:59:08)

Tom Nuñez does, but only because he's a classy-bitch. None of this fru fru sound reflecting stuff. Check out his MySpace it has pics and they look pretty sharp



Ruphus -> RE: finishing inside the guitar (Dec. 7 2011 12:21:18)

quote:

ORIGINAL: etta

Andy; your points about finish seem to make a lot of sense to me. However the Brazilian G. Canin I play (no port) projects better than any guitar I have heard. Could the finish add a reflective/projection effect to the sound?


It should.

Surfaces determine reflection properties.
Basically, the way a tiled wall differs from a carpet-covered one, the sound bouncing properties inside the corpus should vary between rough inner surfaces and fine sanded, and again from laquered.

No?

quote:

ORIGINAL: Sean

Other then an attempt at helping prevent Brazilian Rosewood from cracking I don't see the point. Take Walnut for example, it has a warmth to the touch about it, covering that up with a hard cold finish would just be character assassination


It should be distinguished between sound progression inside the emerging material, and the emission.

From there at least a good part of what is being determined by the walnuts texture should be preserved, even when you finish the corpus from inside.

I think there could be something to Etta´s observation.

When you want to be blown away by your new guitar, do you take it into the bedroom or into the bathroom for reflective amplification?

Ruphus

PS:
And the buffering against humidity changes shouldn´t be worst for the wood either, I´d think.



estebanana -> [Deleted] (Dec. 7 2011 14:50:32)

Post has been moved to the Recycle Bin at Dec. 7 2011 14:51:58



estebanana -> RE: finishing inside the guitar (Dec. 7 2011 14:53:57)

I keep writing snarky posts and deleting them because I can't believe the speculations I've been reading. [;)]

I'm using threads like this to teach myself impulse control. I keep repeating the mantra: it's the internet, and people who are not versed in a subject can and will write about it.

Then I go back to work.



Ruphus -> RE: finishing inside the guitar (Dec. 7 2011 15:07:44)

Though thinking to know a little bit about acoustics, my thoughts were meant as suggestion to see what gives.

If you have either reason to conclude that smooth surfaces do not equal certain properties with reflection, or that sound waves bouncing inside the corpus would be irrelevant to the overall sound of a guitar, you could explain why and help us all with educating.

Wouldn´t that be better than just being annoyed?

Ruphus



etta -> RE: finishing inside the guitar (Dec. 7 2011 16:18:16)

Wow; didn't mean to upset anyone; just asked a question. But, if we go to 12 hole tie blocks to increase pull angle at the bridge, why would the smoke and mirrors of guitar construction rule out attempts at interior finish?



estebanana -> RE: finishing inside the guitar (Dec. 7 2011 17:59:13)

Guitar construction is not about smoke and mirrors. It's about hard won knowledge through trial and error. It's about failure mostly, and through failure you figure out what not to do. You accumulate knowledge through success and failure, some of which is so internalized it can't be articulated verbally, that is because you are articulating that information into instrument as you make it. Music and painting are the same way, some of it can't be explained with words because you are explaining it with painting or notes.

Hernandez y Aguado probably varnished the insides of the guitar because they were trained as piano makers first and they did not know any better.

There is a yahoo discussion group and a book by David Hurd called "Left Brain Luthery" they talk about such things as the break angles over saddles. They talk about engineering ukulele bridges for maximum power an stuff like that. Some more useful, some esoteric not so. You could pose the question to them and they might take it up or point to archives of a past discussion.


But as I love to point out after the spate of "left brain does this" books in the creative world started by Betty Edwards' 'Drawing on the Left side of the Brain', brain scientists have come to the conclusion that hemispheric control of any difference between intuitive and rational tasks is more complex than simply the assignment of the left vs.right brain.

An alternative approach to formulating questions could be gained through the reading of a book by James Elkins called 'What Painting Is'. He talks about the kind of knowledge that is not possible to verbalize because it is a language unto itself that is not translatable. That kind of knowledge has to do with memory and tactile sensation. the same kind of knowledge that it takes to play a musical instrument and develop a touch that creates a personal sound.

Guitar makers get pissy because everyone expects us to explain everything and much of it is explainable. However much of it is not explainable because it is this type of internalized knowledge that is unspeakable in words. Even the most gear headed engineering wonks of the guitar making fraternity are at a loss to explain some aspects of guitar making, although the most dauntless of them will forge ahead into an explanation even when they don't honestly know. ( which is another source of irritation for less "left" brain believing luthiers. )

So we are just pissy all the time because everyone thinks we owe them an education and we constantly have to redefine the terms of the conversation to keep it real. I have to think of ways of politely correcting terminology every time I step into a discussion, it's rather exhausting to keep reading the question itself and having to correct the premise of the question before you answer it.

Read some of this book By James Elkins and try to think about how he relates the tactile memory of painters to guitar makers.

http://www.jameselkins.com/#page27

I'm giving homework because if you want to be educated we have to talk the same language and you have to put as much effort into learning as the guitar makers here put into giving information. [:D]

As for varnishing the inside of the guitar just ask the guys who do it and see what they say. Is it alchemy or rationally based in an acoustic theory? Or is it a purely aesthetic consideration?



TANúñez -> RE: finishing inside the guitar (Dec. 7 2011 21:29:04)

quote:

It's about hard won knowledge through trial and error. It's about failure mostly, and through failure you figure out what not to do.


VERY true.



Richard Jernigan -> RE: finishing inside the guitar (Dec. 7 2011 21:52:06)

quote:

ORIGINAL: Ruphus

Though thinking to know a little bit about acoustics, my thoughts were meant as suggestion to see what gives.

If you have either reason to conclude that smooth surfaces do not equal certain properties with reflection, or that sound waves bouncing inside the corpus would be irrelevant to the overall sound of a guitar, you could explain why and help us all with educating.

Ruphus


It is generally agreed that the upper limit of human hearing is around 20 KHz = 20,000 cycles/second. The velocity of sound in air at standard temperature and pressure is about 342 meters/second. Thus the shortest wavelength of audible sound is a little over 1.7 cm.

Experience with electronic and acoustic signals teaches that path length differences of less than about 1/20 wavelength have little effect on distortion or amplitude of reflected signals. Thus the interior of a guitar would have to have a surface roughness on the order of 1.7/20 cm to alter the loudness of the reflection of the highest audible frequencies. That is, a surface roughness of about 9/10 mm.

I have never seen a decently made guitar this rough on the inside. Just varnishing it would not smooth out roughness of this magnitude.

Furthermore, the output of a flamenco guitar has very little power at frequencies anywhere near 20 KHz. And humans living in civilized areas suffer hearing loss at the higher frequencies, beginning by age 20 or so. (I have been told by my brother, a distinguished physician, and by a Fellow of the American Academy of Audiology that people living in quiet places like the Amazon jungle retain hearing acuity at high frequencies into old age.)

A 43-year career as engineer and physicist taught me very firmly that speculation is nearly useless, except to suggest areas for investigation, and calculation is not to be trusted without experimental verification.

So I side with the luthiers who say experience is not only the best teacher, it is the only one.

RNJ



TANúñez -> RE: finishing inside the guitar (Dec. 7 2011 22:35:26)

Wow that is some really technical stuff Richard. I always marvel when people start taking "fancy" and really break things down and start talking about frequencies and scientific methods, etc,etc because I don't get that involved nor do I know much about that stuff. I basically look in the soundhole and see if it's "shiny" or "flat" lol. That's about as scientific as I get. I think I have actually learned more here on the foro than I ever learned in a University.



estebanana -> RE: finishing inside the guitar (Dec. 7 2011 22:36:01)

quote:

It is generally agreed that the upper limit of human hearing is around 20 KHz = 20,000 cycles/second. The velocity of sound in air at standard temperature and pressure is about 342 meters/second. Thus the shortest wavelength of audible sound is a little over 1.7 cm.

Experience with electronic and acoustic signals teaches that path length differences of less than about 1/20 wavelength have little effect on distortion or amplitude of reflected signals. Thus the interior of a guitar would have to have a surface roughness on the order of 1.7/20 cm to alter the loudness of the reflection of the highest audible frequencies. That is, a surface roughness of about 9/10 mm.

I have never seen a decently made guitar this rough on the inside. Just varnishing it would not smooth out roughness of this magnitude.

Furthermore, the output of a flamenco guitar has very little power at frequencies anywhere near 20 KHz. And humans living in civilized areas suffer hearing loss at the higher frequencies, beginning by age 20 or so. (People living in quiet places like the Amazon jungle retain hearing acuity at high frequencies into old age.)

A 43-year career as engineer and physicist taught me very firmly that speculation is nearly useless, except to suggest areas for investigation, and calculation is not to be trusted without experimental verification.

So I side with the luthiers who say experience is not only the best teacher, it is the only one.

RNJ



Ole'. Ole'. Ole'.



etta -> RE: finishing inside the guitar (Dec. 8 2011 0:35:29)

A simple question on this forum can sometimes elicit amazing responses. An Indian sage, early in the last century said (paraphrasing)..... If you think the world is full of thorns and stones, don't try to cover the whole world in leather, just get a pair of shoes.



estebanana -> RE: finishing inside the guitar (Dec. 8 2011 1:33:03)

The guitar world is rife with unbased speculations, if you make guitars you have to deal with this all time. It's really annoying. It would be like a lawyer explaining what questions were on his bar exam to every client before he could start billing for hours.



Richard Jernigan -> RE: finishing inside the guitar (Dec. 8 2011 2:08:13)

The entire world is rife with unfounded speculations. People will threaten to kill you for disagreeing with some of them.

It is one of the less attractive features of human nature, but I don't think it's going away any time soon.

RNJ



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