The Acoustic Guitar Forum

Go Back   The Acoustic Guitar Forum > General Acoustic Guitar and Amplification Discussion > General Acoustic Guitar Discussion

Reply
 
Thread Tools
  #16  
Old 07-18-2019, 12:42 PM
woodbox woodbox is offline
Registered User
 
Join Date: Dec 2011
Location: West side of WA state
Posts: 2,323
Default

Earl49 just wrote:

"In short, it would be a lot of extra work for no real benefit."

There it is.
Reply With Quote
  #17  
Old 07-18-2019, 12:52 PM
JBCROTTY JBCROTTY is offline
Registered User
 
Join Date: Apr 2016
Location: Southern California (But a Colorado Native)
Posts: 938
Default

This thread made me laugh out loud for sentimental reasons.....

When I was a kid, and to this day, my father, whenever he was/is referring to someone who suffered a loss or took a beating of some kind - financial, athletic, competitive, etc - would say something to the effect of, "That guy took a shellacking," or "That guy just got shellacked."

I never knew where that term originated but I wonder if it came from this french polish that everyone is talking about in this thread.

Carry on the discussion but thanks for making me laugh......
__________________
Justin
________________
Gibson J-15
Alvarez MD60BG
Yamaha LL16RD
Epiphone Les Paul Standard
Fender Player Stratocaster
Reply With Quote
  #18  
Old 07-18-2019, 12:59 PM
Alan Carruth Alan Carruth is offline
Registered User
 
Join Date: Feb 2011
Posts: 4,180
Default

It would be hard to demonstrate any benefit to either tone or durability in any sort of controlled test. There is no agreement as to what benefits might accrue, or how much, but the drawback of using any sort of water resistant coating on the inside is well known: it makes repairs more difficult. There are many reasons aside from rapid drying out that can cause guitars to crack. Any time you repair a crack you will want to reinforce it on the inside. Ant sort of coating will interfere with glue adhesion. It takes time and effort to remove the coating, and the result is not likely to be as smooth a surface to glue to, so the repair will tend to be of poorer quality. Everybody I know who's done much repair tends to be of the opinion that game is not worth the candle.
Reply With Quote
  #19  
Old 07-18-2019, 03:47 PM
rick-slo's Avatar
rick-slo rick-slo is offline
Charter Member
 
Join Date: Nov 2004
Location: San Luis Obispo, CA
Posts: 17,172
Default

Quote:
Originally Posted by Dr Tone Control View Post
I wonder if there would be more effective sound reflection after sanding and application of something more acoustically reflective, would a thin coat of varnish do that?
No.

Want a more purely reflective, less sound box digested, sound then get a guitar with a shallower box depth and a stiffer back. Probably won't like the sound of the guitar as much
__________________
Derek Coombs
Youtube -> Website -> Music -> Tabs
Guitars by Mark Blanchard, Albert&Mueller, Paul Woolson, Collings, Composite Acoustics, and Derek Coombs

"Reality is that which when you stop believing in it, doesn't go away."

Woods hands pick by eye and ear
Made to one with pride and love
To be that we hold so dear
A voice from heavens above
Reply With Quote
  #20  
Old 07-18-2019, 07:17 PM
gitarro gitarro is offline
Registered User
 
Join Date: Oct 2015
Posts: 2,510
Default

Quote:
Originally Posted by Earl49 View Post
There does not seem to be any evidence or consensus that a sealed inner surface would help to contain moisture in the wood. The common finishes used in guitar making are simply not impermeable. A UV cured poly finish might be vapor tight, but nitro and shellac are not. Secondly, fine sanding and sealing the inner surface might slightly affect tone, but only for frequencies that your dog or cat could hear - far above the range of human hearing (20 Hz - 20,000 Hz for a healthy ear).

In short, it would be a lot of extra work for no real benefit.
But imagine all the great reviews you would have from the jazz cats and the blues hounds...
__________________
In the end it is about who you love above yourself and what you have stood for and lived for that make the difference...
Reply With Quote
  #21  
Old 07-18-2019, 07:25 PM
srick's Avatar
srick srick is offline
Moderator
 
Join Date: Sep 2007
Location: Connecticut
Posts: 8,177
Default

Quote:
Originally Posted by Edgar Poe View Post
I always understood they don't seal the interior of the instrument to allow for changes in humidity.

Ed
Ed -

Actually, the shellac just slows down the moisture exchange, but doesn't prevent it. In cabinet work, having both sides of the wood finished is a good way to decrease warpage due to humidity changes.

My guess is that since guitar tops and backs are designed to move, and there is a fair amount of bracing, the humidity\warpage problem has never been a real issue. And when you think about it, less expensive guitars have some really thick poly finishes on the outside and none on the inside - I have never seen an issue with them.

My one thought about this issue is a sonic one: a finished surface would have more reflectivity of soundwaves. Again, it must be a minimal change, otherwise we'd see a lot more of this technique.
__________________
”Lorem ipsum dolor sit amet”
Reply With Quote
  #22  
Old 07-18-2019, 08:19 PM
Wade Hampton Wade Hampton is offline
Registered User
 
Join Date: Sep 2008
Location: Chugiak, Alaska
Posts: 31,166
Default

I know one custom guitar builder who chooses to put a thin coat of finish on the interior surfaces of the instruments he builds. But all of the other hand builders I know do not.

So it's not an unknown practice but it's not a particularly popular practice, either.

Since doing that isn't technically necessary, large scale guitar manufacturers who build their instruments in assembly line factories skip it, because the single most costly procedure that any guitar undergoes is when the finish is applied. It's not costly because of the materials used, but in terms of employee hours because it requires skill and finesse.

That's why Martin and Larrivée's least expensive guitars have satin finishes: because they don't have to be polished to a high gloss. That saves the company a significant amount of man-hours that they’d otherwise have to pay for.

Obviously, a layer of finish inside the body cavity won't need to be polished to a shine, but even spraying a thin layer of matte finish would be an additional production step at a guitar factory, and would require the specialized gear like face masks and a well-ventilated workspace. THEN after those pieces were sprayed the pieces would have to go back out on the factory floor to be fully assembled into a guitar body.

All that for a step of dubious value to the construction of the guitar.

Short version: it's unnecessary and would cost WAY too much money in additional production costs at any high volume guitar manufacturing facility.

Hope that makes sense.


Wade Hampton Miller

Last edited by Wade Hampton; 07-18-2019 at 11:29 PM. Reason: Corrected a typo
Reply With Quote
  #23  
Old 07-18-2019, 08:51 PM
drive-south drive-south is offline
Charter Member
 
Join Date: Sep 2004
Location: Massachusetts
Posts: 4,630
Default

I used to own a Washburn guitar built around 1900 that had the inside sealed with Shellac. It was brw and had more sustain than any guitar I've ever owned.
__________________
"Vintage taste, reissue budget"
Reply With Quote
  #24  
Old 07-19-2019, 09:57 AM
tokairic tokairic is offline
Registered User
 
Join Date: Jul 2019
Posts: 16
Smile

Quote:
Originally Posted by srick View Post
Ed -

Actually, the shellac just slows down the moisture exchange, but doesn't prevent it. In cabinet work, having both sides of the wood finished is a good way to decrease warpage due to humidity changes.

My guess is that since guitar tops and backs are designed to move, and there is a fair amount of bracing, the humidity\warpage problem has never been a real issue. And when you think about it, less expensive guitars have some really thick poly finishes on the outside and none on the inside - I have never seen an issue with them.

My one thought about this issue is a sonic one: a finished surface would have more reflectivity of soundwaves. Again, it must be a minimal change, otherwise we'd see a lot more of this technique.
On the last guitar I built, from Acasia wood, some of the grain was very 'open', so I gave it a light coat of satin poly lacquer. I read somewhere that sealing the inside can have a positive effect on humidity, but didn't say why - so I think you are right when you say finish on the inside slows down the change in wood humidity. Where I live in the UK we have big changes in humidity from day to day (45% - 85% anytime) so slowing the change would be good and it maybe evens out the change somewhat.
The guitar has been out on a stand in my uncontrolled living room for 2 years now and it is still fine, but if I hadn't sealed it, it may still have been fine, who knows?
Reply With Quote
  #25  
Old 07-19-2019, 01:08 PM
MC5C MC5C is offline
Registered User
 
Join Date: Mar 2016
Location: Tatamagouche Nova Scotia
Posts: 1,136
Default

I put a couple of coats of spray shellac on the inside of my archtops before I seal the box. I think it helps to equalize the impact of humidity change, but mostly I think it looks good, and it lets me get sawdust from subsequent building stages out more easily. It costs about a nickle, and it takes about 3 minutes, big whoop after I've spent three or four hours doing a final cleanup and sand of the inside, getting glue spread off of joints, etc. Shellac has the advantage of being very easy to glue to, and in some cases I put down coats of shellac before I glue binding on, for example.
__________________
Brian Evans
Around 15 archtops, electrics, resonators, a lap steel, a uke, a mandolin, some I made, some I bought, some kinda showed up and wouldn't leave. Tatamagouche Nova Scotia.
Reply With Quote
  #26  
Old 07-19-2019, 01:26 PM
nickv6 nickv6 is offline
Registered User
 
Join Date: Apr 2008
Posts: 859
Default

I believe the original Maccaferri guitars had the inside back and sides varnished, not sure about the top.
Nick
Reply With Quote
  #27  
Old 07-19-2019, 06:06 PM
redir redir is offline
Registered User
 
Join Date: Aug 2011
Location: Mountains of Virginia
Posts: 7,657
Default

The only viable reason I see for doing it is that it might make cleaning the inside of the guitar easier. Dust is bad for guitars and it might cling to an unfinished surface more then one with even a very thin single coat of shellac.

As for slowing down changes in humidity? Forget about it, you would need a finish that is an 8th inch thick to effectively do that.
Reply With Quote
  #28  
Old 07-19-2019, 06:55 PM
$ongWriter $ongWriter is offline
Charter Member
 
Join Date: Jul 2007
Location: Lafayette, TN....near Nashville
Posts: 3,529
Default Mr. Everett

I did a workshop in Atlanta a few years back. Mr. Everett's wife would pain the inside of some guitars if the client wanted it. Sorry, no photo's...
__________________
Collings, Martins, Gibsons, Taylor, Fenders, PRS's, a Takamine and MORGAN amps..love them all!!!
Reply With Quote
  #29  
Old 07-20-2019, 06:51 PM
Alan Carruth Alan Carruth is offline
Registered User
 
Join Date: Feb 2011
Posts: 4,180
Default

'Anything sticks to shellac' may be true, but wood glue sticks to wood better than it does to shellac.
Reply With Quote
  #30  
Old 07-20-2019, 07:08 PM
printer2 printer2 is offline
Registered User
 
Join Date: Dec 2012
Location: Middle of Canada
Posts: 5,098
Default

There is no added reflectivity or any sonic benefit to finishing the interior. If thick enough it would help dampen the vibrations as would also happen on the exterior.
__________________
Fred
Reply With Quote
Reply

  The Acoustic Guitar Forum > General Acoustic Guitar and Amplification Discussion > General Acoustic Guitar Discussion

Thread Tools





All times are GMT -6. The time now is 02:59 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright ©2000 - 2022, The Acoustic Guitar Forum
vB Ad Management by =RedTyger=