#31
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Fred |
#32
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Certainly there are some peculiarities depending on the specific application and desired outcome, but to say they have nothing in common is a bit of hyperbole, IMHO. Certainly |
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A good while back I went on a studying spree of finishes when this topic came up on another forum and Alan Caruth I believe linked to some suggested reading.
Anyway at this point the only thing I think a finish is good for is making it easier to wipe off the finger prints and to some extent helping protect against minor dings. If anything the finish does is make the guitar 'worse' so that's why I like the thinnest finish possible, shellac. BTW I think the Selmer/Maccaferri guitars finished the inside of the body but not the top. The thinking there was that no one will ever be able to get their hands inside the petite bouche anyway so you may as well try and protect it. |
#34
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Fred |
#35
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John Bogdanovich’s book recommends finishing the inside, and it never quite made sense why.
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#37
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i believe that there is a certain amount of surface hardening that occurs with a thin wash coat and a degree of barrier protection. there may also be a small amount of reflectance as well.
classical makers H&A used to shellac and do a light fp on the inside. maybe it was part of their unique tone. Last edited by arie; 06-05-2018 at 09:01 AM. |
#38
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In guitars the soundboard braces are acting similarly to breadboard ends in that they are running long grain across the grain of the sound board. Except they’re worse as they’re glued across the whole width....Generally a no, no, in Woodworking. The reason they work is that the soundboards are quartersawn, narrow, and generally speaking excessive humidity fluctuations are avoided. The finish has pretty minimal affect one way or other. In fact one could very well build a top with a single piece of flat sawn wood. As long as the humidity level never changed it would be fine finished or not. However even if you coated both sides of the top with a thick layer of polyester finish, if you then took it to a much different humidity level, (ie. build in the desert and move to the ocean), that finish will not prevent the top from self destructing. Lastly regarding finish, different finishes have varying levels of hardness. They all protect the wood though and make the surface significantly tougher than raw wood. Even a light lacquer or shellac finish adds a lot of protection vs raw. That is the main job of the finish on an instrument. Jeff |
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#40
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Ultimately, the point remains that you can't really consider one product's standards as acceptable or sensible to another's. A 2x4 is made of very specific low grade wood, dried very specifically, machined very specifically. Flooring is made of different species, dried completely differently and machined completely differently...same true for lots of other products. To my point, these other scenarios being offered have little in common with one another other than being made of wood, so you need to consider the entirety of the product to understand why the standards and practices vary greatly. |
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#42
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Last edited by dneal; 06-06-2018 at 06:20 PM. Reason: combined quotes |
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#44
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Herb Hunter wrote:
"I don’t think the term, transducers, applies to acoustic guitars, they are passive radiators." Actually, IMO, guitars are precisely transducers: devices for changing one sort of energy into another. In this case they change the somewhat regular application of force by your right hand into sound. With a bit of an assist from your left hand it can even be musical! Note that guitars are not 'amplifiers': they don't use an external power source to reinforce a small signal and turn it into a louder one. All of the power comes in from your hands, and most of it is 'lost' in the process of being turned into sound. |
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I see this supposition all the time. I've spent a lot of time looking at absorption data for a wide variety of materials (34 years full time in the acoustics business) and near as I can tell, the only difference that might occur in absorption / reflectivity of sealed versus raw wood occurs at 30 kHz and above - a far higher frequency than a normal human ear has ever heard. Our range of hearing is typically 20 Hz - 20 kHz. Even a dog or cat might not hear frequencies that high, except in their youth. It is quite the technical challenge to even measure absorption coefficients at those frequencies.
Off topic, but I believe similar things about the arched or bowl backs of guitars (GS Mini, certain Guilds, Ovations, etc). Many people readily accept that the arch makes a big difference in reflectivity and therefore tone. It might make some difference in cancellation / reinforcement of certain standing waves inside the "box", because of non-parallel surfaces. But I would expect the difference to be subtle - perhaps even imperceptible - in almost every case. The arched construction makes for stiffer back, which would have an effect on overall reflectivity, however. JMO.... |