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I'm a builder, not a repair guy but I find myself needing to replace the bridge on one of my older instruments. Bridge is mad rosewood glued with hide glue. Can anyone point me to a good Bridge removal tutorial or help me with what temperature is required to release the glue?

Thanks.

BTW, this is an 000 with a wrc top from Brock and mango back/sides from the zootman... so it has very olf vibe.

John Hall and Beau Hanaman have good tutorials on Youtube.

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Hannam…

I've only removed a couple of bridges, and none with hide glue.
With that said, If I were doing it, I would shoot for 160F neighborhood for a hide glue bridge. I use a 180F max temp setting with TB original. It takes a while for the bridge to heat up and transfer that heat to the glue so don't get in a hurry. The bridge may never even get to your set temperature.

With my rig it takes 15- 20 minutes from power on (bridge shaped silicon heater with a temp controller/ thermo couple and ebay bridge clamp) for glue to start to soften and another 5 minutes to completely remove the bridge. I use a similar process for removing fingerboards but 200F set point- the thermocouple will get that temperature but the fingerboard likely will not. Maybe others will chime in...

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Measure Twice,

Karl Borum

Hide glue usually needs a combination of heat and moisture to release. With moisture, 120-130F is sufficient get it to release. But, it is slow. It takes a while for the moisture to move from the gap through the edge of the unreleased section, so you have to be patient or you’ll peel up some of the top. I put a few drops of water into whatever gap between the top and the bridge that got me deciding to remove the bridge. I heat the bridge with a small iron (I don’t measure the temperature—I just get it hot—it takes a while to get the heat all the way through the bridge) and work a slender palette into to the gap. Paying attention to the grain direction of the top, so that I don’t go into it, I continue the heat and work the palette enlarging the gap. It can take me in excess of twenty minutes to get the whole bridge loose after I can feel the palette start to go in.

The problem with the heat and the moisture (and the palette) is that you can damage the finish. So, depending on what your finish is, you have to worry about what you’re doing to it. I use EM6000 on my guitars which succumbs to heat, moisture (the water on the bare wood under the bridge gets into and raises the grain under the finish), and alcohol. I use some white stonewool insulation around the bridge to protect the finish from the hot iron.

Alcohol and hide glue react nicely sometimes. Wicking alcohol into the gap and applying a little bit of pressure with the palette sometimes gives a very frightening crack and then a loose bridge. I don’t get to do that often because the alcohol would wreck my finish.

Cedar often sheds a layer with the bridge. This can make your removal even more difficult. Too much pressure and the cedar will come apart internally leaving you a nice mess to clean up. You may wish to make a new bridge and just rout the old one off. Make a jig to support and guide the router so that you can rout all but a very thin layer of the bridge off which you can then remove with a subsequent pass or with heat, moisture, and a chisel.

If you have a nitro finish, don’t use blue masking tape to protect the top. The adhesive in the tape can react with the nitro and spoil it.

It wouldn’t hurt to glue up a dummy bridge/top and practice the removal before you go to the good guitar. Please practice so that you don’t blame me if something doesn’t go as I’ve described. I’ve done many, but there’s often something I didn’t expect or a top divot that I have to fix.

The palettes I use are art supplies. They taper in thickness down to the tip. The tip wrinkles under pressure, so eventually, I have to get another palette. I consider them expendable.

Titebond glued bridges are easier. All they need is heat, the palette, and a bit less patience.

I use a small travel iron and small palette knife. I like to start the heat and reach in and feel the temp of the bridge patch. When it gets warm, I start the removal. I always try to avoid over heating the center seam of the top. I don’t want that opening.

A few things to consider:

- The springy, thin blades of palette knives want to follow the grain, so determine whether any significant run-out is present (there is ALWAYS some, but often not something to worry about if << a degree). A quick check on a spruce top is the light/dark inspection done looking from tail block towards headstock, with eye at about a 45 degree angle to the bridge. Wood fibers are like a bundle of drinking straws: if looking into the ends of the bundle of wood fibers or of drinking straws, they will appear dark due to internal reflection away from the eye. If viewing the sides of the straws or wood fibers, they will appear lighter in color due to reflection of light back to the eye. A top will often show that dark/light change, with darker colored side indicating that the grain is rising towards the eye and lighter colored side having grain rising away from the eye. Bridge release should be worked with the tip of the palette knife moving into grain rising away versus towards the tool. On guitars with top run-out, it is common to work from the tail block-towards-soundhole on one side of the center line of the top and soundhole-to-tail block on the opposite side.

- Modify your primary bridge removal tools with a slight upwards bend (1-2 degrees max) about 1/4" to 3/8" or so behind the tip... this allows the knife to be worked into either a net-shaped bridge patch or pocketed bridge while still steering the tip away from top when working the center of the patch.

- Clean and buff your removal tools before doing the job - this reduces the chance of a bit of hardened hide or a slight burr from scratching the finish. A Rival hot pot or similar filled with 150 degree water keeps the blade wet and warm for the work, and makes removing dead Titebond a bit easier in case you happened to have used that adhesive for the job. I buff my tools before use on the same 8" low speed buffer that I use for final fret buff... buff then wipe any residue off the blade before use.

- Most bridge removal blankets do not extend full width, to I start on one side and work to the other with a blanket move or two. I find using the typical 5 watt/square inch blanket running on a router speed control set at the top of the yellow or orange or bottom of the red takes 10-15 minutes of heating to be ready for removal. Higher temps risk compromising the center seam or bridge plate, so for the first few tries, note how long it takes/temp setting to get to the ability to work the blade into that initial edge.

- On tools, I like the RGM brand of Italian-made knives carried by Dick Blick... the #81 is excellent, and the wider #84 - once the serrations are ground off and edges radiused/smoothed - handle the main removal task. A 40mm/1-1/2" wide Liquitex #8 rectangular blade with serrations round off and edge polished and radiused (or similar) is handy for keep the already-separated half of the bridge from reattaching while working the other side.

https://www.dickblick.com/products/blic ... word%3DRGM

https://www.dickblick.com/items/liquite ... number-8-/

- Avoid adding too much water and swelling the bridge patch edges... a little goes a long way. Dip the knife in hot water and whatever is carried into the joint is usually enough. If the edges of the finish show texture once the bridge is off, allow the top to dry for a day or two before re-gluing the bridge. Tough on a pro schedule, but better than having to factor in a spot refinish.

- It is often useful to consider pulling a PSA-attached pick guard if it is so close to the bridge that it interferes with removal... probably another thread to cover all the ins and out of that job would be useful. Naphtha and patience help.

- The goal is to remove the bridge without any excess top wood transferring to the bridge... take the time to adequately heat the joint and avoid the urge to impatiently work the stubborn bits... as the boys often reminded me, slow is smooth and smooth is fast.

Listen to woody.

It's common practice in the violin world to open hide glue joints dry. Dry hide glue is brittle, and has low peel resistance, so it will often fracture before the wood does if you do it right. Adding water makes the glue more flexible and thus a bit tougher, while it weakens the wood. Many violin makers have a thin and flexible knife that has a long wedge section. The edge is thin, but not sharpened; it will follow the glue line without cutting into wood fibers. In many cases it helps to actually apply hand pressure over the place where the edge is, to keep it from wandering.

The brittle nature of hide glue favors methods that apply a shock to the glue line. I have heard of folks placing a wood block along the front edge of a bridge and hitting the block a sharp blow with a hammer. I've never had any luck with that myself,: I suspect itr works best when the glue line is old and the bridge is peeling a bit in the first place. Learning to 'read' the glue joint is an important part of repair practice...

Modern cold-set glues tend to be more flexible and tougher than hide glue, so heat and moisture are usually needed to get them apart. Titebond and the ilk will usually release at ~140F; wait'll you see what that can do to a finish. Leaving a strung-up hammered dulcimer in the back seat of a parked car in the summer can be an adventure in distortion. While Titebond will soften with water, it's slow, and in my experience the wood can soften about as much. Acetic acid is the solvent for most of those 'white' glues. Be sure to use a stainless steel knife when you use it: acetic acid and iron makes a permanent black stain.

For some reason this little video always comes to my mind when thinking about removal of bridges from guitars.
https://www.youtube.com/watch?v=t5Q4iUBXNEM
Guess I'm just twisted.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Thanks everyone, lots of good info above.

Finish is French polish shellac, so I probably shouldn't be using alcohol or water.

I fired up the glue pot and glued up a bunch of practice parts to help learn the disassembly process.

His youtube channel is a massive rabbit hole worthy of further exploration.

For what it's worth, unless it needs to be used on another instrument, I would much prefer routing a bridge glued with hide off if it's not going back on.

I'd plane or rout down until I just had a skin of the bridge left then scrape, chisel, etc.

To me the enemy is re-finish work. Making a new bridge is Nothing compared to that potential can of worms.

The "reversibility" of hide glue I think is tossed around too lightly.
It's very difficult to use moisture in bridge removal without swelling, puckering, etc. and again you risk finish work.
Without moisture hide glue holds like the devil without VERY high heat.

To me the beauty of hide glue is it holds in high heat and you don't have to remove any precious top wood. Once the bridge wood is removed the layer of remaining hide glue in the top will just make for a better joint on the next bridge. PVA lets go with very low heat and all the plastic saturated spruce should be removed before re-gluing.

A guitar's practical lifespan is often determined by how well the top wood under the bridge is treated over the years.

Just a thought.

Bridges glued with HHG are generally the easiest to remove. John Hall produced a video years ago with the shock method.

https://youtu.be/TYg8sEjxgpc?si=qsT599lyhcrbKn_L.

The cold shock method works much better with hide glue as it tends to shatter like glass. Without additional moisture, hide glue is actually somewhat resistant to heat.

Aliphatic glues (Titebond, etc,) will require heat to soften and a careful touch to convince the gummy glue to release without pulling up fibres.


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Listen to Mr. Carruth - as he and others mentioned, shearing the bridge-to-top joint with a sharp hammer tap can work - especially on those guitars that already have a more-or-less clean release going due to some other ongoing reason.

The main issues with shearing the joint are where there is considerable run-out in the top (to include figured top timbers such as curly koa or other acacias, curly mahogany) or where the shear strength of the top is rather low (e.g., western red cedar... especially large curl figure), considerable top wood can be lost to the effort. Another complication with this approach arises when the bridge is deeply pocketed... something seen more frequently than one would like, and generating additional issues as the hide in the pocket is placed in compression versus shear. As Mr. Carruth implied, the ability to read the joint - aka, experience - is the most effective 'cheat code' a repair person has available where bridge removal is indicated.

I have seen the issue of easy removal dismissed by builders with the statement that the bridge should never come off a guitar stored and transported properly, but most repair people will have seen enough incorrectly placed bridges, failed saddle slots, body refinishes, 'too high/too low' bridges, etc. to discount that view of need to pull. I have done rout-offs before where there is no desire to retain the original bridge for either reglue or pattern, and that usually simplifies the job at the expense of a bit of clean-up work.

With all the respect for others experiences, my comments are just where I often come down.

There are certainly many times when an old (usually) Martin hide glued bridge on a top with some run out is already lifting and I KNOW it will pop right off with almost Zero damage in seconds and that's just what I do. This could be like that. As woody says, that "can work". Is it lifting? Is there significant run out? (much easier). Is it an old joint? Is there a rabbit ledge on the bridge?

Again, with respect, the top around the bridge in John Hall's video is fairly rough to begin so its hard to compare it after removal. If you manage to stop the video around 3:25 and a few seconds forward, There is simply more top stuck to the underside of the bridge than would be acceptable to me. Especially if it was unnecessary.

Maybe the difference of opinion is partly one of goals. And each person and guitar is certainly a different situation.

Good info above, thank you.

May I piggyback on this thread to discuss removing a bridge glued with fish glue? Temps? Moisture needed? Other differences? Not sure the shear method will work here. I have a bridge blanket ordered.

For the record, this bridge is an ebony pyramid bridge, glued very well (not lifting on any edge) and the top is carpathian spruce with a maple bridge plate. Need to add compensation and I'll be using a new brazillian rosewood bridge with the same footprint but without pyramids...and the saddle slot will be tilted rearward a bit.

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Formerly known as Adaboy.......

Darryl, have you considered adding nut compensation? Basic nut compensation comprises understanding how much saddle-only compensation is needed per string (which I think you already know, to be contemplating removing the bridge), dividing that distance by two, then putting that amount as nut movement toward the first fret (on a per string basis) for nut compensation and halving the amount of saddle-only compensation you require. It might get you out of a fairly risky procedure of removing a well glued down bridge.

There are other, simpler, nut compensation schemes (e.g.moving the whole nut forward the same amount for all strings) which give a better result than saddle-only compensation, but not as good as doing it all on a per string basis, that might still get you out of removing the bridge.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

In my limited experience with it, it seems that fish glue is noticeably tougher than hide glue. Dry removal, which would be my go-to with hide glue, could be risky.

Since you're not planning on saving the bridge planing it down as close to the surface as possible, followed by a bit of warmth and moisture, would be the way I'd go with that one.

But first I'd do as Trevor suggests, and see what you could accomplish with nut compensation. Even something as simple as a toothpick under thre string against the nut can tell you a lot, and you won't need to trim off the end of the fretboard to find out. It's saved my bacon a couple of times on repairs.

Thanks for the suggestions from two great minds.

Trevor, I have your books and have considered adding nut compensation...likely will after replacing the bridge. The guitar was setup for 1/2" saddle height but the pyramid bridge is a bit too short for that. This leaves the saddle too tall if setup at the ideal 1/2" the guitar was sides/radius were designed for. So I want to replace the bridge with a standard height bridge with more appropriate saddle height that has the saddle angled rearward a few degrees so the saddle stays more vertical after string tension is applied (little belly then add the tall saddle creates a bit of rotation...sound great though!). Then after doing this, I still may need to add some nut compensation to intonate ideally.

I think your suggestion to route this bridge off is likely the best one since I'm not reusing it. Would still like to hear anyone else's experience removing a bridge glued with fish glue (or a fretboard etc.) just for my own personal knowledge.

BTW, I didn't mention this but this bridge was glued on maybe 12 or 13 years ago.

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Formerly known as Adaboy.......

For what it's worth, after several tries with block of wood glued to soundboard cutoff I ended up routing the bridge off.
Reversability of hide glue seems to be overrated.

No worries. If it's gotta go, it's gotta go.

There's no way I'm a bridge removal expert, but my experience has been that getting a bridge off intact that was properly stuck on, with minimal damage to the surrounds is an exceedingly difficult and time consuming task. By properly stuck on I mean closely conforming, fresh surfaces, rapid closure and high pressure. Basically hide glue best practice regardless of glue type.

As it happens, I have a drop-in, re-top job to do soon. First task is to get the bridge off so I can swing a router over a clear top. This gives me an opportunity to experiment with bridge removal procedure. What I will be doing will be routing/planing the majority of the bridge off to as thin a residual strip as I dare. I will be using the bridge slotting router jig for that (Fig 4-96 and Fig 20-47 in the book). Routing bears the risk of raising a top resonance and the bouncing top giving an irregular cut, so I finish off with a plane. I don't use a plane all the way because of the CF (and bone in the case of classical bridges) in the bridge. I'll start with a block plane and finish (with planes) with a convex finger plane (Fig 4-11). Then move to a dog-leg chisel (see Fig 20-25, same as I use for clearing finish) to complete the job. All done with no water and no heat.

In a more normal bridge removal scenario, I'm pretty sure I could make a new bridge in less time than trying to get one off intact and with much less risk to the rest of the guitar.

Good luck with it, whichever procedure you use!

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Trevor—

Would a brace jack and some towels inside the guitar help reduce the top vibration during routing?

I don’t do repair work, so this is merely curiosity talking. If I ever need to remove more bridges in the future (I’ve done a few the hard way), I’m definitely going to rout it off next time. Making a new bridge is fun; getting an old bridge off is not.

That would probably help. I try to avoid raising any resonances primarily by speed control of the router (nothing inside the guitar). The one time I had a resonance was using a largish cutter (5.00mm, ~3/16") and slow rotational speed. Using an up-cut spiral cutter (1/8") toward the high end of the router's speed range (a Makita RT0700C) has worked fine when cutting saddle slots with the bridge on the guitar. So I'll be using that setup and lots of light passes.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

I generally just put a thin card stock mask on the top around the bridge and remove the material with a hand plane. It doesn't take long. It can be scraped thinner with care before wetting it, and the remainder usually peels off nicely. I realize this might not help Trevor with the CF laminations, but on a plain wood bridge it works fine.

A few more thoughts on bridge pulls:

- A sharp, 1/4" spiral up-cut bit and a good trim router with expanded baseplate is my tool of choice for a rout-off. I have certain router bits reserved for certain jobs, and a 1/4" Whiteside spiral up-cut is - while certainly expendable tooling - preserved for use on tasks which may be a bit fraught if using dull tooling. Observe the RPM recommendations given by the bit manufacturer... but recognize that higher speeds will likely cook resins onto a bit. A sharp bit tolerates resinous timber to a greater degree that a dull bit, but somewhere in the 20,000 rpm no-load speed seems to be fast enough to avoid hazardous resonance and slow enough to avoid smoking the bit.

- A pair of 18" x 4" x 1/2"/12mm cork-face plywood cauls elevate the router base off the top such that the initial passes don't result in bridge/baseplate interference. These cauls may be the same ones used when employing brace jacks for bracing reglues. 1/8" cork place mat material is relatively inexpensive and if kept clean, protects top finishes.

- Pickguards can be troublesome, but an extra layer of 1/16" or 1/8" cork can shim up the cauls to avoid issues with depth-of-cut setting.

- 315g hot hide is lovely for keeping a bridge on an otherwise troublesome top, but gel temperature of about 135 deg F means that removing that last .030"-.060" scrim needs a bit of moisture in the wood and careful application of heat

Beyond that, repetition helps re: any repair-oriented operation such as bridge removal/reset, as those that have worked in busy, full-service repair shops will likely attest. De-risking the job with a rout-off is smart for builders that might have far more experience fabricating/installing bridges than on bridge removals where the goal is to reuse that bridge. Time spent on duplicating a bridge is likely a fraction of the time spent on structural and cosmetic repairs where the bridge is uncooperative during removal,