Applying guitar bridge- no mando content

[Rick Lindstrom]

For those of you that also make guitars, a question-

In years long past when I was making guitars, my method for applying the bridge was to scribe around it, scrape off the lacquer and then glue on the bridge.

I've read in a couple of sources lately that the way to do it is to mask around the bridge and use paint remover to take off the lacquer before gluing on the bridge. Seems like an OK method, but I worry about residue from the remover compromising the glue joint. And maybe paint remover getting under the edges of the tape and ruining finish.

What do you guitar-builder folk do to remove lacquer from the bridge footprint area?

[David Houchens]

I scribe (lightly) around the bridge which is located with the bridge pins and use a hot knife to blister the lacquer, then remove with a chisel. Much care is needed at the edges, but it works fine.

[J Caldwell]

For those of you that also make guitars, a question-

In years long past when I was making guitars, my method for applying the bridge was to scribe around it, scrape off the lacquer and then glue on the bridge.

I've read in a couple of sources lately that the way to do it is to mask around the bridge and use paint remover to take off the lacquer before gluing on the bridge. Seems like an OK method, but I worry about residue from the remover compromising the glue joint. And maybe paint remover getting under the edges of the tape and ruining finish.

What do you guitar-builder folk do to remove lacquer from the bridge footprint area?

Rick,

Lots of ways to do this , but I do it the same way you do. Takes about 10 minutes. It's what I'm comfortable with, but it's certainly not the only way.

[sunburst]

I mask the bridge footprint with masking tape before applying the finish material, but I mask it just a little smaller than the bridge. After finishing, I lay the bridge in place and scribe around it as usual, then pull the masking tape off and scrape the edges of the bridge area of the top.
FWIW, Martin did a similar thing. They used to scrape the whole bridge footprint, but later they had precut bridge-shaped masks that they applied to the tops before finishing. Now they use a CNC router to remove the finish (and a little of the top wood, so the bridge is very slightly inlaid into the top making it quite a bit harder to remove a bad bridge later in the life of the guitar). They still "tooth" the spruce before gluing the bridge, believe it or not... or at least they did last time I took the tour.

[Rick Lindstrom]

I mask the bridge footprint with masking tape before applying the finish material, but I mask it just a little smaller than the bridge. After finishing, I lay the bridge in place and scribe around it as usual, then pull the masking tape off and scrape the edges of the bridge area of the top.
FWIW, Martin did a similar thing. They used to scrape the whole bridge footprint, but later they had precut bridge-shaped masks that they applied to the tops before finishing. Now they use a CNC router to remove the finish (and a little of the top wood, so the bridge is very slightly inlaid into the top making it quite a bit harder to remove a bad bridge later in the life of the guitar). They still "tooth" the spruce before gluing the bridge, believe it or not... or at least they did last time I took the tour.

John-

I did it the same way back when on all of the guitars I made. The thing I remembered about that was how difficult it made it to wet sand and polish out the lacquer on the top. Not impossible, but less easy than if that tape weren't in the middle of the soundboard. This time I decided to wait until after spraying and polishing to lay out the bridge foot print. Lazy I guess :)

[sunburst]

I have some very thin masking tape and I can sand right over it after a few coats of lacquer. By the time it's ready to buff I can treat it like the mask isn't even there. (Of coarse, the lacquer usually sands through into the tape a little, but that's no problem.) I find it more difficult to scrape the lacquer off of the whole bridge footprint without damaging the surface of the top wood.

[MikeEdgerton]

They still "tooth" the spruce before gluing the bridge, believe it or not... or at least they did last time I took the tour.

By tooth do you mean cross hatch the area that the bridge will sit on? I was taught to replace bridges that way after clean up. Has that technique changed?

[sunburst]

At martin, they had scrapers with notches filled into the edges and they used them to scrape that familiar pattern we see on glue surfaces of many old instruments we repair. Here's the back of an F2 peghead with the overlay removed. The tooth marks are still mostly visible. It was thought that the striations gave the glue a better grip by providing a rough surface for a physical grip. Studies have shown that a smooth, freshly prepared surface gives a stronger, better bond than a toothed surface, so toothing has fallen out of favor with builders and repair persons. Dick Boak (who was leading the tour that I was on, along with many other builders) said something like: "I know, studies show that a smooth surface is better, but we have done tests and this works best for us.".
Here's my hypothesis on that:
At Martin, the bridge glue surface is prepared ahead of time, and right before gluing the bridge a worker tooths the area. I suspect that the refreshing of the surface caused by the tooth scraper is what improves the joint, and they would do well to simply scrape or sand the area smooth right before gluing rather than using the tooth scrapers, but... what do I know...
FWIW, when replacing or re-gluing bridges, I (and many others) strive for a smooth surface on the top and the bridge, but the smooth surface must be prepared no longer than 15 minutes before gluing.

[MikeEdgerton]

That's pretty much what I was taught to do. I thought Martin did as you've shown and Gibson cross hatched the same surface. It does make sense that a smooth surface would be a better glue joint but then again I've never had one I repaired fail... yet. Thanks.

[Tavy]

Question: does this mean that guitar builders are unable to string up in the white? Do any do so, and if so how?

Thanks, John.

[sunburst]

Classical guitar builders sometimes string up "in the white" (though rosewood backs and sides and mahogany/cedar necks aren't white) because the classical guitar tradition has the bridge glued before finishing, and the bridge finished over. I don't know of any steel string guitar builders who string up their guitars before finishing. Why might they want to?

[Dale Ludewig]

I've done a few guitars strung up in the white. It's not the same as stringing up a carved top mandolin in the white. But StewMac sells brass pin-like thingies that go through the bridge. They're basically a flat head bolt with a hole bored through the center. You put your bridge in position (using a jig like they sell to get your saddle location accurate) and bore your bridge pin holes. Then these things go in, bolting the bridge to the top. I usually only use two on the outside strings (high E and low E). Bolt the bridge to the top. You can actually ream the other holes to shape and use regular bridge pins. Then you can adjust the whole business to where you want it. Saddle height, nut slots, the whole thing.

At that point, I take the bridge off, mask the area where the bridge sits, put the bridge back on and scribe the masking tape, take the bridge back off, cut the masking tape back slightly from the bridge outline. Then I'm kind of where I think John was describing. I spray the guitar and I will probably scrape a little lacquer off after all is said and done to get the bridge to sit right back where it was. This method doesn't require much work after things are buffed out.

[Rick Lindstrom]

Thanks everyone for the wonderful replies. If I make another guitar in this lifetime, I think I'll try the method outlined by John and Dale. In the meantime, I'm going to mask, scribe and try the hot knife to carefully take off the lacquer. I'm sure a little scraping will be involved too.

I'm wondering now about using a heat gun or mini butane torch to lift the lacquer while the top is masked, but that sounds like a recipe for heartbreak. LOL There's also lacquer to be removed where the end of the fingerboard will be, and since it's a larger area, I might try masking off a small spot in its boundary and testing the heat gun/ torch approach.

[John Arnold]

I use heat all the time to repair vintage guitars, but I see no sense in risking bubbling the lacquer to do this on a newly-finished top. I just scribe around the bridge with an XActo knife and use a small chisel to remove the lacquer. If the lacquer is fresh, it will peel off the surface. Sometimes I mask about 1/8" inside the perimeter, which speeds up the finish removal somewhat. I have also done a full mask, but the thickness of the mask makes it difficult to buff the lacquer smooth all the way to the bridge.

[Rick Lindstrom]

I use heat all the time to repair vintage guitars, but I see no sense in risking bubbling the lacquer to do this on a newly-finished top. I just scribe around the bridge with an XActo knife and use a small chisel to remove the lacquer. If the lacquer is fresh, it will peel off the surface. Sometimes I mask about 1/8" inside the perimeter, which speeds up the finish removal somewhat. I have also done a full mask, but the thickness of the mask makes it difficult to buff the lacquer smooth all the way to the bridge.

We'll see what happens with the scraping. I've been working on this guitar in starts and fits for quite some time. I think I put the finish on about 6 months ago, or more, so it's probably pretty wll cured out by now.