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Hello friends - long time no talk. I've been out of the luthiery game for some time now, and am dipping my toe back in. An acoustic that I build for a buddy needs to have the bridge reglued. I recall that the technique requires some gentle heat on the bridge to loosen the glue, before gently sliding a spatula with the grain. Can you please advise on the best way to get this bridge off without damaging finish or underlying sitka top? Thank you.

You just told it to yourself!

_________________
"I've been had again"
Tim Benware
Creedmoor, NC

Yep - as you described it. Did you use a glue that softens with heat (Titebond, hide glue)? If you used epoxy you are going to have trouble. The only other thing to add is to be careful of grain runout that could invite your spatula to penetrate the top. Read these wise words from Professor Ford:
http://www.frets.com/FretsPages/Luthier ... inrun.html

Thanks, gents. No, no epoxy - never. Don't remember, believe it or not, but either Titebond or HHG. And thanks for the reminder on grain runout.

Hey Corky!

We use a 250 watt heat lamp and cardboard wrapped in foil (reflective side out) shields that fit the bridge perfectly with no gaps exposing guitar top wood and finish.

1). I heat for maybe a minute with the light nearly touching the bridge and moving the lamp from middle to a wing and back again getting the wings too.

2). Then I test with my palette knife. I want the glue to feel gummy and having it give with some pressure. Being mindful of runout too as you mentioned is prudent. I often determine runout direction and then put a piece of masking tape on one half of the guitar with an arrow on it to remind the dotard here of the runout direction.

3). Usually I'm not happy with how soft the glue is not... after the first pass so I put the shield back on and reheat. I may reheat 3 - 5 times before the bridge is completely off. We want the glue joint to give way, not be lifting any wood fibers and of course never damaging the top in any way either.

WARNING: I always stand right there when using a heat lamp and using it that close to the work. Expect to maybe see a puff or smoke, smell and or see some oils rise to the top of the bridge especially with BRW and smell that wonderful smell of BRW in the morning. . I unplug the lamp immediately when I am done.

Regluing the bridge for us is:

1). Use HHG and a methodology that respects the short open time of the glue and the requirement for excellent surface prep and wood-to-wood fit. HHG is not a good choice for filling gaps and gaps are not desirable at all.

2). Clean up the bridge patch on the guitar meaning have a completely freshly prepared wood surface, no old glue.

3). Clean up the bridge bottom.

4). I fit the bridges meaning I scrape and radius a bridge bottom with either my belt sander or a razor blade scraper or both. I'm looking for my bridges to stay completely down in the proper place with only minimal finger pressure. YMMV others I know don't do this and lots of folks smash... flat bottomed bridges on domed guitar tops, f*ctories do this too and it can work fine as well... or not. Scrape the bridge bottom just before applying the glue. Squeeze out is desirable and insurance that you used enough glue.

5). Clamp well and often and with HHG do it in 15 seconds or less. I preheat the bridge if it's only wood in the microwave with my burrito that's still in there from yesterday. 15 seconds in a 700 watt microwave works for me (for the bridge not the burrito).

6). I leave things clamped until the next day but we have pulled clamps sooner when the show had to go on.

Now we rabbit our bridge bottoms and make a pocket in the finish after cleaning away the tons of finish that most makers leave under bridges that are also part of why their bridges lift..... Is this necessary, no. We believe our results are better over the long term so we do it with guitar with thicker finishes on them. Guitars with very thin finishes such as shellac we may not pocket and rabbit the bridge.

I don't like clearing finish to the bridge perimeter. Why? because if it ever lifts again the likelihood of a clean removal with no visible top damage is greatly reduced. So we clear finish very nearly to the bridge perimeter, maybe .020" or so and our rabbit on the bridge bottom (again not required) is made to match.

BTW Titebond original is fine for a bridge glue. We prefer HHG but lots of bridges have been glued on with Titebond and are doing fine.

Hope you are too.