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Tape off bridge/fretboard on top before finishing or not?
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Author:  Woodie G [ Tue Apr 27, 2021 6:11 am ]
Post subject:  Re: Tape off bridge/fretboard on top before finishing or not
Tape mask...there will be a few thousandths finish intrusion into the top, requiring removal of that sealer and finish material. A mask eliminates that finish intrusion, so less scraping and a thicker top after finish cleanup, whether net-shape or pocketed install.

We have a very nice, brand-new custom guitar in the shop for bridge reglue...the guys think it is a bad batch of hide/late closure of joint, but I am betting on a rout off that did not get quite deep enough to clean off the sealer penetration into the spruce.

Frisket comes in several thicknesses...the 0.002" is a little easier to trim and apply, and is about half the thickness of a lacquer finish after initial sanding and buffing. The thinner 0.001 frisket we have is higher tack, although we seldom see fiber pull on removal. That aside, 3M 2090 blue tape at .0035 is about final lacquer thickness, and holds enough lacquer in the show surface to avoid sand-through or blueing a buffing wheel, shows good lacquer exclusion on edges and substrate, and has perfect tack for the job.
Author:  Glen H [ Tue Apr 27, 2021 7:11 am ]
Post subject:  Re: Tape off bridge/fretboard on top before finishing or not
Terence Kennedy wrote:
Glen H wrote:
I think I’m the loner here. I use paste paint stripper after finishing. Virtually no scraping to do, other than the dried stripper.


The original StewMac VHS tape that came with their kits in the 90’s showed the gel paint stripper technique. I never tried it. Kind of scared me.


Scared me too! I first saw it on Charles Hoffman’s website. After scoring the bridge outline. I mask off the top with paper and use an artist brush to paint the stripper on. The thing is, when it dries, it comes off real easily with a razor blade. I used to get tooling marks on my tops from true scraping and using a router scares me more.
Author:  johnparchem [ Tue Apr 27, 2021 7:47 am ]
Post subject:  Re: Tape off bridge/fretboard on top before finishing or not
Woodie G wrote:
Tape mask...there will be a few thousandths finish intrusion into the top, requiring removal of that sealer and finish material. A mask eliminates that finish intrusion, so less scraping and a thicker top after finish cleanup, whether net-shape or pocketed install.

We have a very nice, brand-new custom guitar in the shop for bridge reglue...the guys think it is a bad batch of hide/late closure of joint, but I am betting on a rout off that did not get quite deep enough to clean off the sealer penetration into the spruce. ...



I did have a few bridges come off on instruments where I did not tape and scraped off the finish with a razor blade until I thought all of the finish was off. I never considered the few thousands of finish intrusion into the top. In fact I was careful not to scrape into the wood trying to keep the gluing surface level. I switched to taping off the bridge some guitars ago, but now I understand why I was having trouble.
Author:  Hesh [ Tue Apr 27, 2021 7:57 am ]
Post subject:  Re: Tape off bridge/fretboard on top before finishing or not
This is a more complicated question than do you tape or not. As you can see from all of these answers it's also highly dependent on what finish is to be applied.

For example if cat Poly were the finish good grief and good luck cleaning up the bridge patch with a sharp chisel. You can still do it but it will be a lot of work if you are doing more than cleaning up a tight perimeter.

Some finishes chisel off way easier than others obviously.

And I'm in the school that the best glue joint is unadulterated, well prepared and recently scraped (15 minutes from gluing) wood to wood (with glue of course...).

When I was building all of mine were taped off and all of mine were glued on with HHG on well prepared surfaces with the glue foot print very close to the bridge foot print. I only had one bridge lift out of 54 guitars and he left it in a hot car in the summer for a week at the Nashville airport so I'm not assuming blame (or credit :) ) for that one.

Lastly as someone who routinely cleans up bridge patches of OPOG (other people's old glue :) ) it's WAY easier to carefully cut off well placed Frisket film than cleaning up the entire patch. You will also have an easy, accurate way to measure your film thickness on the most desirable real estate on an acoustic guitar, the bridge patch. It's frisket thickness minus what your measurement is.
Author:  Tim Mullin [ Tue Apr 27, 2021 8:05 am ]
Post subject:  Re: Tape off bridge/fretboard on top before finishing or not
Take the time to prepare and locate the bridge precisely — it’s not so difficult — then preserve a perfect, uncontaminated top patch under tape, in my case thin frisket film. Works under virtually finish.


Sent from my iPad using Tapatalk
Author:  Alan Carruth [ Wed Apr 28, 2021 9:29 am ]
Post subject:  Re: Tape off bridge/fretboard on top before finishing or not
I tape off just a little (3 mm or so) under size all the way around. That's enough to get past the build-up around the tape edge when you're cleaning up, and enough to allow for reasonable adjustments in location. That last bit of varnish around the edge comes up well with a sharp chisel, and then the whole area gets scraped to get the surface energy up right before gluing. So far...

You must be extra careful when you scribe around the bridge on cedar tops, particularly the back edge. Cedar (and redwood) have much lower peeling resistance than spruce, and a cut into the wood is a stress riser where the peeling load is highest. I've seen bridges come up with 100% wood shear, from deep scribe cuts around the perimeter.

Also, while we're at it; the best joint is smooth. 'Toothing' the top within the bridge footprint just makes a weaker joint, and makes more problems when the bridge needs to be re-glued, particularly if there is any run out in the top.
Author:  jfmckenna [ Wed Apr 28, 2021 2:56 pm ]
Post subject:  Re: Tape off bridge/fretboard on top before finishing or not
I think you guys who take routers to you finished guitars are crazy. But I guess it works and you have not had any problems yet. The operative and key word here is, yet :) Because one mistake and....

When I am ready to glue the bridge down I remove the tape which is smaller than the footprint, or in the case of shellac no tape, an then lay down a large piee of tape covering the whole thing. Then I put a piece of doublestick to the bottom of the bridge and position it carefully and push it in place to the tape grabs it a bit. Then with a brand new and sharp Exacto blade score a line around the bridge just enough to go through the thickness of the tape and to score the finish. Then I remove the tape foot pring and scrape away.
Author:  Barry Daniels [ Wed Apr 28, 2021 3:27 pm ]
Post subject:  Re: Tape off bridge/fretboard on top before finishing or not
Taking a sharp blade to scribe around a bridge is crazy! ;-)

I actually have less nerves with a small router than I use to when I used knives and chisels.
Author:  Tim Mullin [ Wed Apr 28, 2021 4:18 pm ]
Post subject:  Re: Tape off bridge/fretboard on top before finishing or not
I’ll second the warning about scribing around a bridge. Yes, it can be done, but it can also result in catastrophic failure. Cedar tops are particularly problematic as it is so easy to damage the fibre integrity. A disproportionate full half of my bridge reglues are cedar-topped guitars, where the scribing is evident. Many of the other half are Asian-made guitars where the factory had fanciful ideas about what constitutes a good glue joint. I otherwise do rather few bridge reglues on spruce tops.


Sent from my iPad using Tapatalk
Author:  doncaparker [ Wed Apr 28, 2021 4:49 pm ]
Post subject:  Re: Tape off bridge/fretboard on top before finishing or not
I think an appropriate tip for those who have scribed too deep would be to go ahead and remove severed fibers inside the bridge footprint, because they don't make a very secure gluing surface once they are severed. In other words, cut/sand/shave a bit of a "pit" for the bridge, if you have severed fibers. It's better to have the bridge sit a few thousandths lower than to have it glued to wood that is barely connected to the rest of the top. Adjust the depth of the overhang as needed (if you do the overhang thing).

Of course, the better advice is to not scribe that deep. You just need to scratch the finish so there is a visible line. Cutting through the finish can come later. Scribing doesn't need to do that.

Regarding the routing of finish: I can't speak for others, but it's not like I'm plopping my Porter-Cable 690 on top of the guitar. I use a Foredom and a StewMac Dremel type router base, with a relatively small end mill. It's all very civilized. :D
Author:  Bryan Bear [ Wed Apr 28, 2021 7:53 pm ]
Post subject:  Re: Tape off bridge/fretboard on top before finishing or not
I made a version of the saddlematic with pins that are the same diameter as my saddle rout. I rout my saddle slot at the angle I want and drill the pin holes. I tape off the bridge area and put the saddlematic pins into the saddle slot. The saddlematic then positions the bridge based on where the saddle needs to be. I clamp the bridge down (with my bridge caul inside the box) and drill the outermost holes through the top, plate and bridge caul. I carefully scribe around the bridge with a sharp blade taking care to only cut the tape. Now I have a masked bride footprint and holes for my locator pins all the way through the bridge caul. I cut a small amount around the perimeter of the bridge so it is ever so slightly above the finish to bare wood transition.

Gluing the bridge down is easy. The caul goes in and the locator pins are just proud enough to not rise above the top of the bridge. Warm the bridge, put on the glue, place it down and clamp.
Author:  Woodie G [ Thu Apr 29, 2021 6:32 am ]
Post subject:  Re: Tape off bridge/fretboard on top before finishing or not
Keep in mind that open end grain - whether due to a rout-down or an excessively deep scribe - is an invitation for additional water from waterbased glues to be passed into the deeper fibers of the top. As I heard from the first day here, water moves wood, with proof seen in post mortem inspections where the finish separated from excessive swelling around the bridge/top joint. Proper glue consistency and avoiding the creation of large amounts of unsealed end grain addresses the issue - we use 315g and mix for a set viscosity.
Author:  Hesh [ Mon May 03, 2021 1:36 pm ]
Post subject:  Re: Tape off bridge/fretboard on top before finishing or not
When scribing the goal is to cut through the finish not the top.... We've scribed just inside of the bridge foot print on every bridge reglue (and the occasional first gluing that we may do when ghost building) on every guitar that we have ever worked on that needs the bridge glued on. We've never had a failure and that's because we only cut through the finish.

But you're right Tim there are people who go too deep and that can lead to a nightmare also especially on WRC.

In our business we have a saying that "Cordoba" the maker of WRC classical guitars actually means "bridge reglue" in Spanish....

Here's when going back to tooling up for Lutherie 101 will help. Uber sharp chisels always pointed away from you (remembering the Padma) are your friend along with careful, gradual scribing of the finish line.

Lastly IIRC Mario used a router to clear bridge patches. Dave Collins won't do it with a router and Dave will place a router on the top of a prewar Martin with his saddle mill. I like a sharp chisel.
Author:  jfmckenna [ Mon May 03, 2021 6:17 pm ]
Post subject:  Re: Tape off bridge/fretboard on top before finishing or not
LOL I love the Cordoba joke becasue it's true!

I probably scribed too deep on the first several guitars I've made but I have it down now. The trick is, it really doesn't take much pressure and ALWAYS use a new blade. Any chef will tell you that the only time they cut themselves was when using dull knives. It's the same here. With a very sharp blade you get the job done in one sweep with light touch.
Author:  phavriluk [ Mon May 31, 2021 1:30 pm ]
Post subject:  Re: Tape off bridge/fretboard on top before finishing or not
It depends on build configuration. Fingerboard extensions that are bolted to an extension of the neck block don't need any finish removed from anything. No glue.
Author:  phavriluk [ Mon May 31, 2021 1:36 pm ]
Post subject:  Re: Tape off bridge/fretboard on top before finishing or not
To add an echo to comments about using sharp blades: I bought a box of 100 #11 scalpel blades, including a handle, for less than ten bucks. There's sharp hobby blades, and there's scalpel blades, which for some reason are cheaper than hobby blades, and vastly sharper (but weaker, they break in my rough hands).
Author:  Juergen [ Mon Sep 05, 2022 1:54 pm ]
Post subject:  Re: Tape off bridge/fretboard on top before finishing or not
Has anyone tried the other way gluing the brigde and fretboard extension first and then apply the finish?
What disadvantages may this way bring up?
Author:  Hesh [ Tue Sep 06, 2022 3:03 am ]
Post subject:  Re: Tape off bridge/fretboard on top before finishing or not
Juergen wrote:
Has anyone tried the other way gluing the brigde and fretboard extension first and then apply the finish?
What disadvantages may this way bring up?


Juergen the reason why the vast majority of steel string makers do not finish with the bridge on is it makes finishing and sanding a bit more difficult when it's in the way and it can be added later with no down side. There are also some advantages in not only installing the bridge after the neck is on but milling the saddle slot too only after the bridge is installed, you can nail the scale length with great precision.

Further it's recommended to finish with the neck off so the neck joint remains serviceable come neck reset time. When a guitar like Guilds are finished with the neck on the neck to remove it has to have the finish cut through and this can cosmetically mess up the neck joint area and it makes the reset more difficult and finish touch-up more complex. Guilds have way too narrow a heel too and they break but I digress.

So it's recommended for serviceability and ease of finishing and for steel strings to finish with the neck and bridge off the guitar.

One pro finisher I know will not finish a guitar is the neck is on and another pro finisher I know wants the neck on, only. :? :D Both are concerned with their own methods and not the serviceability aspects after it's complete.

For classical guitars it's the reverse, the tradition is to finish with neck on and bridge on although a classical could also be finished just fine with the bridge off.
Author:  Juergen [ Mon Sep 12, 2022 3:07 am ]
Post subject:  Re: Tape off bridge/fretboard on top before finishing or not
Hesh, thank you for your reply. After reading this thread, my personal decision is clear: finishing after glueing everything in place! There are a lot of reasons for my decision:
to build in a rim in the bridge for overlapping the finish reduces the gluing surface about 10 %! This weakens the area with the highest stresslevel caused by the pull of the strings enormously. Especialy that the downside rim of the bridge lays over the finish creates an ideal tacklepoint for the string pull to lift the bridge.
Both discussed modes creating a bunch of possible mistakes, from thinning the top wood when cleaning from laquer to the tape leaving very small amounts of adhesive on the top. All results in weakening the glueing area and increase probability for bridgelifting or even bridge pulloff. I think this are the reasons for that you have so many repairs of lifted or pulled off bridges in your shop.
I will make the finish in the real meaning of the word as the final step of the building process. To manage the possible difficulties I have to practise practise practise for perfecting my skills!
Excuse me, but our meanings about what is a pro differ. For me a professionel is someone who handles a given task perfect, in your case of a pro finisher it wouldn`t matter if the bridge and neck are glued on ore not. He would make a perfect job in both cases. What would you think about a carpenter you want to build you a closet in your house and he would say "Ok, but first you have to remove this wall and rebuild the floor! Because I can only build closets 4 meters x 2,50 meters x 50 cm." Is that a professional? Never!
Author:  WudWerkr [ Mon Sep 12, 2022 8:26 am ]
Post subject:  Re: Tape off bridge/fretboard on top before finishing or not
Tape Always
Author:  bluescreek [ Mon Sep 12, 2022 9:05 am ]
Post subject:  Re: Tape off bridge/fretboard on top before finishing or not
it doesn't really matter
I rout them off I am not a fan of tape as it makes level sanding a pain
Author:  Clay S. [ Mon Sep 12, 2022 9:54 am ]
Post subject:  Re: Tape off bridge/fretboard on top before finishing or not
As much as I love routers, I tape and scrape. A misadjusted or slipping router bit can ruin your day in so many ways. oops_sign [headinwall]

Hi Juergen,
As amateurs we are allowed to shoot ourselves in the foot, and explore possibilities that make no sense to the professional. That is how we learn - often that the advice we didn't take was good advice. There are other reasons why finishing with the bridge on is sub-optimal, which may not be immediately apparent. It will mostly be a PITA for the "next guy".

Amateur instrument builder since the 70's
Author:  Juergen [ Mon Sep 12, 2022 11:27 am ]
Post subject:  Re: Tape off bridge/fretboard on top before finishing or not
Hi Clay,
that`s the real truth, that we as amateurs can make a lot of mistakes without having nothing to eat next week :)
But as Hesh describes it is commen in the classical world to finish after glueing everything in place. On the other hand lifted or pulled off bridges are his daily repair work, and I have tried to find a possible answer in the way finishing is done beyond all other possibilities like bad glueing, not well done glueing surfaces etc.
Author:  Eric Reid [ Mon Sep 12, 2022 11:37 am ]
Post subject:  Re: Tape off bridge/fretboard on top before finishing or not
French polish finish. Cut finish off with chisel (see avatar). No scraping or sanding.
Author:  James Orr [ Mon Sep 12, 2022 11:54 am ]
Post subject:  Re: Tape off bridge/fretboard on top before finishing or not
After scraping the finish off for a bridge last night I decided to try taping off next time.

Just a thought I haven't seen mentioned yet, but aside from having the bridge pre-located, you should also either have your bridge made beforehand, or shape it off a pattern of some sort so you know the patch will match the new bridge precisely.
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