Beeswax For Inside The Guitar

Construction and repair of Classical Guitar and related instruments
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Re: Beeswax For Inside The Guitar

Post by rojarosguitar » Thu Mar 16, 2017 2:07 pm

romanticguitars wrote:Humidity yesterday outside my shop was 5 percent... I have used shellac in the past to try to keep moisture trapped inside... I have played a venue Gallup once where my guitar dried out and all the strings mysteriously started buzzing... as soo as I got it back in the case it cleared up. I agree with James about the repair issue but dryness here is tough.
5% - oh, boy. One could move to the Mars as well. Unfortunately not much chance to hear a lot of music there... quite rarified atmosphere :cry:
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Douglass Scott
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Re: Beeswax For Inside The Guitar

Post by Douglass Scott » Fri Mar 17, 2017 7:10 pm

RedCliff wrote:Never tried to make an instrument to survive in 5% humidity. But, if you are going down the route of sealing the inside for this reason then why not go the whole hog and coat it with a thin layer of something such as a spar varnish or even Rustins Plastic Coating (is that available in the US?) which for those who don't know is a two-part cold cure finish, based on Urea Formaldehyde resins, plasticised with alkyd and reinforced with melamine. You can epoxy over it if you need to. Just an idea, better that than a broken guitar.
Important to understand that coating a guitar inside and out with any finish doesn't form a perfect seal. You can't actually make a guitar climate proof. Moisture will always transfer between air and wood, just more slowly with finish than without. What romanticguitars is doing is for the purpose of shipping, traveling from home to lessons, etc.. When you have to take your guitar outside, the interior finish buys you maybe a few extra hours? I'm not sure how long, it would depend heavily on what the finish is... before the guitar feels the dryness. I'm sure you're correct that a seriously tough film would buy you the most time possible, but it would also drastically (yes, I think drastically) affect the sound, and you're into the repair complications again. No free lunch!

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Re: Beeswax For Inside The Guitar

Post by RedCliff » Fri Mar 17, 2017 10:57 pm

I take your point Douglass. I guess it depends what the outcome is you are hoping for. I would suggest that in any wood, even if the change of humidity is bound to occur, you still want it to occur as slowly as possible in order to minimise the likelihood of a crack due to rapid changes. That is why we coat the ends of timber to protect the end grain from rapid loss of moisture. We know it will lose the moisture some day, but hope to slow that change and reduce the checks.

Does coating the insides slow that enough to make a difference? I don't honestly know. I suspect it depends on a whole bunch of factors including the type of finish. I would bet it takes a long time for wood to lose moisture if it is encased in melamine, more than a few hours. My sea kayak is encased in epoxy and gel-coat - moisture does not get in, no matter how long it says in the water, so it is theoretically possible with some finishes at some thickness to almost eradicate that transfer of moisture. It would be easy to test on wood if someone had the time and inclination, just coat all sides with different finishes at different thicknesses of some test pieces after ensuring they have the same moisture content and then seeing how quickly it falls in a low humidity environment. I bet it does vary between different finishes and of different thicknesses.

But as you say - that may be a trade off in terms of acoustic properties. Drastically? I'm not so sure. I know tradition says yes, but i'm not sure blind tests would agree. Stephens research in the Savart on the effect of finishes on the vibration properties of soundboards covered in different finishes shows that they all actually increased the Q factor. There are obviously upper limits to the thickness of a finish that you can't cross if you want good sound, but I'm not sure what that is, depending on which finish is used. Classical tradition says Shellac is best, particularly emphasised by luthiers - but then we would, as it separates us from the factories.

What % loss of acoustics is deemed acceptable if it stops you having to repair your guitars all the time? If you coat everything with a finish that means it takes you twice as long to affect repairs, is that a problem if you only need repairs a third of the time? I don't know - 5% humidity is just off the chart to me, so I would imaging it would probably take some quite drastic approach to interior finishing (and exterior) to make any difference.
Giles Ratcliffe

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Re: Beeswax For Inside The Guitar

Post by attila57 » Mon Mar 20, 2017 10:11 pm

romanticguitars wrote:Just wondering about something... I sometimes like to put a thin coat of shellac one the interior sides and back plate braces before closing up the box... I know some builders do this and I have occasionally. But today as I was working on my students guitar I wanted to seal it up some since she lives here in New Mexico and she lives on a ranch where she doesn't have the best climate control. Don't necessarily want to use shellac so I took a little beeswax and rubbed it on a section of the Indian rosewood near the tail block. I like the way it just naturally seals the wood and doesn't make the inside of the guitar smell like a paint store... anyone else use it? Thoughts?

Don't put anything in the inside of the guitar, only if you won't be sorry if you have to discard it in the end. I have learnt this truth the hard way. I had a cheap plywood backed Aria guitar and I decided to impregnate the back to improve the tone and the look. Now I have it in pieces in my scrapwood cabinet...

Attila :bye:

PS: If you need further details of how this accident happened, I'll be happy to provide details.
Music to hear, why hear'st thou music sadly?
Sweets with sweets war not, joy delights in joy...

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Alan Carruth
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Re: Beeswax For Inside The Guitar

Post by Alan Carruth » Wed Mar 22, 2017 1:59 am

RedCliff wrote:
"That is why we coat the ends of timber to protect the end grain from rapid loss of moisture."

Not exactly. Due to it's structure wood tends to lose or gain moisture quickest through the end grain. Sealing the ends is done to make the moisture loss equal through all surfaces, as much as possible. This does slow it down, of course, but more importantly it keeps the ends from shrinking more than the center of the piece, so that end checking doesn't get started. If the loss is even through all surfaces you can dry woood quite quickly without problems.

I live and work in New England, which is as close to 'guitar hell' as you'll get. We see rapid and large swings in temperature and humidity all year long, as well as weeks of either very low indoor humidity when the weather is cold, or very high when it's hot. When I did more repairs the big season for cracks was right about now; February or March, after the worst of the cold weather, when things had had a chance to 'soak' in the low humidity, as it were. The rapid changes of the spring or fall were not nearly as problematic. Builders around here learn to take the weather into account, by doming the top, for example, so it's got some place to go when it shrinks. Coating the inside is not common, nor is it particularly helpful as far as I can see.

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