Official Luthiers Forum!

Owned and operated by Lance Kragenbrink
It is currently Fri Mar 29, 2024 11:04 am


All times are UTC - 5 hours





Post new topic Reply to topic  [ 5 posts ] 
Author Message
PostPosted: Sat Jul 25, 2020 12:30 pm 
Offline
Walnut
Walnut

Joined: Fri Jul 24, 2020 7:23 am
Posts: 1
First name: bob
Last Name: carwell
City: liberty hill
Zip/Postal Code: 78642
Country: United States
Focus: Repair
Status: Amateur
I removed a bridge on moderate value Korean built classical guitar. Discovered it was not glued onto bare wood but onto the guitar's finish (lacquer ?).

Should I glue the new bridge back onto this finish or try to take its footprint on the guitar surface down to bare wood so I have a nice wood-to-wood glue joint ?

If you advise gluing onto the existing exposed finish after I clean it up and smooth it, what glue should I use ?

And if you advise taking it down to bare wood, how do I do that ? Just sanding ? Or is there a liquid like naptha or something that will liquify the lacquer to make scraping/sanding it off to bare wood easier ?

I am (obviously) a neophyte and any advice would be much appreciated.

Best,
Bob


Top
 Profile  
 
PostPosted: Sat Jul 25, 2020 2:17 pm 
Offline
Koa
Koa

Joined: Sun Sep 16, 2007 1:27 pm
Posts: 705
Location: United States
First name: Dave
Last Name: Livermore
State: Minnesota
Focus: Build
Status: Semi-pro
Bob,
If you want it to stick, you need a wood on wood glueing surface.

I scrape with razor blades until close then sand.

Good luck


Top
 Profile  
 
PostPosted: Sat Jul 25, 2020 2:53 pm 
Offline
Brazilian Rosewood
Brazilian Rosewood

Joined: Thu Nov 04, 2010 1:46 pm
Posts: 2124
First name: Freeman
Last Name: Keller
Focus: Build
Status: Amateur
One of the most common failures on acoustic guitars is the bridge comes loose. One of the most common reasons for this is the finish wasn't (adequately) removed before the bridge was attached. With lacquer I use chemical stripper, then a chisel and sanding to get to bare wood, then good quality wood glue and clamps. Make a good caul that fits over and around braces so you don't crush them - you want to apply clamping pressure to the bridge plate if there is one.

The top may have a slight dome - if so the bottom of the bridge should be sanded to match.

I'm slightly surprised that the bridge on a classical was attached to the finish - most of the time classicals are finished after the bridge is installed and it is finished too.



These users thanked the author Freeman for the post: Dmaxwell (Sat Jul 25, 2020 11:06 pm)
Top
 Profile  
 
PostPosted: Sat Jul 25, 2020 5:01 pm 
Offline
Brazilian Rosewood
Brazilian Rosewood

Joined: Fri Aug 19, 2005 4:02 am
Posts: 3227
Location: The Woodlands, Texas
First name: Barry
Last Name: Daniels
I am not surprised that is was glued to the finish on a Korean built guitar.


Top
 Profile  
 
PostPosted: Sat Jul 25, 2020 5:26 pm 
Offline
Koa
Koa
User avatar

Joined: Wed Jan 14, 2009 3:14 am
Posts: 982
Location: Shefford, Québec
First name: Tim
Last Name: Mullin
City: Shefford
State: QC
Zip/Postal Code: J2M 1R5
Country: Canada
Focus: Build
Status: Professional
Conventional wisdom is that bridges need a wood-to-wood bonding surface. But there are builders who do quite well attaching steel string bridges to polyester finishes using CA. It would still need to be a good fit to minimize the glue line.

Many cheaper guitars have a partial footprint scraped through a thick finish to the wood inside the perimeter of the bridge, leaving a rim of finish around the outside. When they glue the bridge, they end up with a hopelessly thick glue line as the bridge rests on the rim of finish. They come off will little persuasion. They would be better just to leave the finish and glue with CA.


Sent from my iPad using Tapatalk


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 5 posts ] 

All times are UTC - 5 hours


Who is online

Users browsing this forum: No registered users and 16 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
Powered by phpBB® Forum Software © phpBB Group
phpBB customization services by 2by2host.com