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Well, finally the law of averages caught up with me and I put a bridge on in the wrong spot.

It was glued with HHG. Is there anything particularly different about HHG in the removal process? More time more heat?

Any tips?

Thanks..l

The beauty of hide glue is how easily reversible it is. I just use a small heat blanket to heat up the bridge without heating up the surrounding finish. Just be patient, and let the heat do it's work. I set my temperature controller to midway, which I would guess is about 250°. I'll then use a couple of small painters spatulas and just a little water on the tip, and slowly start working that in under the bridge, being very careful not to dig into the top. Before you know it, between the heat and the moisture, that bridge will give like a loose tooth.


Ken Jones
Mountain Song Guitars

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Mountain Song Guitars www.mountainsongguitars.com

Let's hope...

Here's our current approach and we remove and reinstall bridges daily.

1) Use or make a thick cardboard shield with a cut-out the exact shape of the bridge. Cover the shield in a quality, thick foil (reflective side up...).

2) View the gutiar top sighting from the head stock down the neck and note the runout direction(s) for the two halves of the top. I typically put a piece of masking tape on one side with an arrow drawn on it in the direction of the runout for that half of the top. This is important because inserting pallet knives against the runout can result in lifting fibers and digging into the top. Of course the other side of the half has the oppisite runout direction but you know this.

3) Install the protective/reflective shield and then use some of that reflective duct type tape, the shiny stuff... reflective side up and bridge the gaps in the shield onto the bridge top. It's OK to cover the peremeter of the bridge with the goal being to protect the finish on the top.

4) We use a 250 watt heat lamp (never leave unattended...) and heat up the bridge from the top moving the lamp from side to side to get the wings hot too. Avoid too much heat and you will know when you have enough heat in the next step.

5) Paying attention to runout direction insert pallet knives with the runout and I typically start at an area already lifted a bit. What you want to feel is the glue being a gummy mess. If you hear crackling either the glue has not softened or you are lifting fibers. If it needs more heat heat some more. Also after working an area with the pallet knives you may want to reheat a bit too to get that gummy feeling back.

6) Work carefully and deliberately again never leaving that lamp unattended when on. Water is not required especially with a recently glued on bridge.

7) With some patience and understanding the feel of softened glue and keeping it at the right temp to soften the glue it's very possible to remove cleanly with no lifting fibers or top damage.

8) If your pallet knives have never been used before consider taping off the collars that can scratch the top when one is not careful.

That's it, easy peeze and I love the smell of old, stinky HHG in the morning. In fact I typically remove bridges in the mornings because I am cold and the lamp heat feel great.

This is not something I enjoy. I tend towards hulk smash. All I have is a clothes iron...

What temp does the glue loosen?

And what he average overall time for the process?

Sighting down the top to identify run out direction, please explain which side is which grain direction? Is the darker side running up towards me?

With a clothes iron, the wool setting. Silk is too cool, cotton too hot. If the glue up was recent it will soften quickly - maybe 2 mins initial heating, 5-10 more gently inserting your palette knife or equivalent and reheating as necessary. But don't rush. Old glue takes longer and needs some moisture.

Be careful with the water, too much can pick up the color of the bridge and wick it into the grain of the top. A permanent tattoo.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Not good enough to salvage the bridge, but hopefully good enough to salvage the guitar...

https://www.youtube.com/watch?v=TYg8sEjxgpc
been taking them off this way for years. Learned this at CF Martin
it is a lot easier than you may think

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

It just like a recently mowed lawn where you can see the striping from the mower moving in different directions. In the case of the lawn the darker side/rows are with the grass leaning toward you and vice versa for the other side. We are speaking of how light refracts by the way.

When we sight down a guitar top one side may, not always, be darker than the other side. The darker side has the grain running out toward your position or perspective and since we book match the other side will be the reverse. A very well quartered top with minimal runout may not look any different from side to side and that's great. But if there is a difference in darkness observing and respecting the runout direction when inserting pallet knives lets the knives skim over the top and not dig into the runout.

Make sense?

We don't use water very often if at all these days with HHG including on pre-war Martins (WWII for the critics....).

The preference for the heat lamp is that unlike a blanket or iron (we have these too but don't like them...) of which both rely on conduction requiring direct contact a heat lamp heats the entire bridge top regardless of dimensional and height differences in the bridge style so the wings get a healthy dose of heat too with no physical contact. It's also faster and since you asked just like how I bend sides it's a feel thing and I can't give you precise times but the initial heat lamp heating with the lamp very nearly in contact with the bridge is a minute or less. A little smoke is not a bad thing too nor is the the oils in Rosewoods coming to the surface but that's the upper limit of the heating time and likely better just below this point.

Typically I will heat, test, reheat a bit, work some of the bridge and then reheat again. With each session the shield is placed to heat or removed to use the knives.

BTW Stew-Mac's new big-mutha bridge spatula is wonderful and highly recommended.

Ed that's more damage than you typically want but hey it's a good first effort.

In this case, because you can, I would replace the bridge but for bridge removals with our method we never remove wood from the bridge and very little if any from the top. Some guitars are just going to suck and of course too there is the damage done (not the Neil Young tune...) from the bridge lifting in the first place that often lifts fibers and can leave shreds of the bridge on the top too.

Super sharp chisels are your friend now to remove all old glue and crap from the top so that you have wood-to-wood surface to reglue the bridge to.

FYI we do a micro rabbit around the bridge permitter that is around .005" inset and .003" deep depending on finish thickness. It's a nice look to have the finish tucked under the bridge and no visible glue line and since we are only inletting the rabbit say .005" we are not leaving any gluing area on the table. Many bridges that we see from individual builders and especially f*ctories can have finish on the top NOT removed for a perimeter of 1/4"..... inside the bridge foot print. Not to mention that where the bridge spans the edge of the finish the wood-to-wood contact sucks there and a bit inland too.... Not good. I once calculated that one manufacture was leaving nearly 40% of available gluing surface with stinkin finish on it.....

Oh well...

Ed: A heat lamp with suitable insulation( corrugated cardboard wrapped in aluminum foil) around the bridge works a charm. Even heat, easily controlled, and you can check temp by feel, your eyes on the bridge through the process.
Tom

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A person who has never made a mistake has never made anything!!!

Well, more or less ok. Unfortunately, the little bulge where the pallette knives bend left dimples all over the top. Salvageable as a second at least...
Sure enjoyed not having to scrape the old glue off.

I prefer going forward not back, and this is a good reminder of why I contract out my major repairs to a repair centric luthier.

John,

Lost way too many guitars at the old job to be comfortable with that on mine. I was hoping the heat factor would be smooth like buttah. C'est la vie. It's only the 2nd 2nd out of a hundred guitars, so meh.

Anyone in the market for a cheap nl00?

The pallet knives you get at chef supply stores for icing cakes, etc. are much better than artist pallet knives. The edges don't curl, or bend, but are the same thickness. I found this out when my son enrolled in chefs school, and I had to buy all his equipment.

Bob

Good tip. What's the price like?

Just did a quick search, looks like they call them icing spatulas - about $6.50 on Amazon.

Kevin Looker

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I'm not a luthier.
I'm just a guy who builds guitars in his basement.
It's better than playing golf.

Hesh, my ledge is around 3/32 or so around the perimeter and about the same depth as you .005 to start and a little sanding to bring it down tight. The reason for a 3/32" rout is that if you come to close to the perimeter the finish can chip out beyond the area of the bridge and then you're in trouble. In 30 years of building I've never had one come up, but my bridge profile is slightly larger than the typical belly bridge or pyramid bridge.

Cool and results most certainly matter. Your 3/32" is WAY better than the up to and at times over 1/4" of inset finish that we see on the instruments of various manufactures so good on you David!

It took me a while to get to as little as .005ish" because I don't see as well as I used to.... It's true that the closer that we remove finish to the perimeter of the bridge the more risk there is that finish will flake or chip in a visible area. But... scoring well though the finish and lots of experience with super sharp chisels also negates this risk to a large degree. So far my finish removal has stayed where I want it to be - knock on BRW....

John, does this method work for all types of glue or just HHG?
thanks, Mike

I used this on all glues.

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it