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I glued my back on #2, using Fish Glue, and trimmed it down before I took it out of the solera. The center brace didn't glue right, as it caught on the center strip. I thought it was down, but no. I got some glue in there and got it glued down, but after I did, I realized that that brace was a bit too short. Not sure why, as it was radiused at the same 25' as the other two. What it does, is create a little dip in the back. It's only a couple of mm, but it shows in certain light, and I know it will look terrible after finishing. Any way, I figure now is the time to fix it, before I do any more work on it. With Fish Glue, do I still use an iron, and work around the back and across the braces to get the back off? I figure that my best choice is to replace that brace, leave it high, and re-radius in the back using a sanding stick radiused to 25'. Any tips on getting Fish Glue to Release? Are there any other issues I should be prepared to face while doing this? Any tips that will make it easier? I have some pallet knives that I can work around the back with. Should I wet things? I don't want to make everything come loose. Will I have to replace the linings too? For what it's worth, I glued the braces in the body before gluing on the back.

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Waddy

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Treat it just kile hid glue

Funny because I have a fish glue back removal in my future due to a screw up as well. I have removed fish glue bridges before I and will say it takes a fair bit of heat and that you definitely want to get moisture into the joint.

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David White, Toronto

"All my favourite singers can't sing."

I dissagree with addng moisture. It is not needed and the glue will let loose at about 120f-140f.

Now moisture will help soften the fish glue but your wood will asorb more of it than the glue will.

The glue should let loose with just heat, but one thing you have to remember about the thin plates is that to much heat can really dry them out and can actually crack them. So, when taking off a back, I'd use a moist cloth under the iron to warm the edges and over the braces, especially over the head and tail blocks. You don't want to have to fix a cracked back too.

I learned this the hard way when I was working in a cabinet shop many years ago. Yes, heat is good to loosen the glue, but to much heat will crack thin plates, so some moisture it good. To much though will warp it, so just a damp rag is all you need.

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What's it going to do to the "decorative" back strip?

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Waddy

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Try not to focus any of the heat near the back strip and you'll be fine. Keep the heat an inch or so away from it and when you're working you blade under the plate, warm the blade up so it will do the heating of the glue under the back strip locations. Actually, warming the blade up will make the entire process go easier too. If you can, just warm the blade in a pot of water, that way there's a small amount of moisture on the blade and it's warm to boot.

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"There's really no wrong way, as long as the results are what's desired." Charles Fox

"We have to constantly remind ourselves what we're doing....No Luthier is putting a man on the moon!" Harry Fleishman

"Generosity is always different in the eye of the person who didn't receive anything, but who wanted some." Waddy Thomson

Thanks, Rod. That's helpful. Makes me less nervous.

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Waddy

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Since your guitar has no finish on it, you could even glue a small cross grain splint of wood over the back joint at the top and bottom which could be latter carved off. The splint would reinforce the center joint and inlay, and prevent any delamination.

Also, since you are going to be leaving the braces attached to the rims, your back removal will be more complex as you will also have to slowly detach it from the braces. The splint described above could also be used over the brace locations. This might seem like overkill, but having to also remove the braces will have you heating up the back near the center joint in more places giving more risk for joint failure.

Waddy, that looks like rosewood. If so, watch that the oils in the wood do not bubble to the surface (too much). Just to minimize sanding and so on.

Mike

Thanks Mike.

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Waddy

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I dunno Michael - I had to take a fish-glued back off (classical, neck set incorrectly) and found that it was much more resistant to pure heat than other glues I've used (titebond, etc). I'd try a lot more moisture if I had to do it again.

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Jim Kirby
kirby@udel.edu

I believe that's what Rod was suggesting. Dave White also said the same thing over at LuthierCom.org. - i.e., pallet knives soaking in hot water. I'll use a wet rag between the iron and the wood, that'll generate some steam type moisture too.

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Waddy

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Waddy I use hot wet pallet knives, and plastic wedges to stop loosened part re-gluing.

Of course a brave man would wipe alcohol over the area and set fire to it .

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

Waddy, I just got mine off so here are a couple of thoughts while it's fresh in my mind.

- be extra careful on the widest part of the upper and lower bout its easy to split the wood there
- it's a fairly long job so keep a focus, the palette knife can end up cutting into the wood easily instead of sliding between the two pieces of wood
- I had a couple of areas that seemed tough and applying the heating iron to the knife while it was in the joint seemed to help conduct the heat right into the glue

Good luck.

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David White, Toronto

"All my favourite singers can't sing."

Well, now, that was about the least fun 3 hours I've spent in a while!

It's off, but not without some collateral damage. Looks like the braces are toast! They were Spanish Cedar, and I got too much wood. It was hard to tell when the glue was releasing. I discovered quickly that the wet hot knife was the best tool. The back was pretty cupped when I finished, but I suppose that's from all the heat and water I was using. I wet it, flattend it out, and put some weight on it. There is one crack in the upper bout, near the heel, but it'll glue up just fine. I think I'll wait till it all settles down. Tomorrow, I can get the braces out and make another set. I believe all the linings are OK except one little spot, but I have some that I can splice in there.

I guess I'm just glad to have it off. I'm glad it wasn't someones prize guitar, that I trashed the braces on. Live and learn!

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Waddy

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Here are the results of my efforts.

Back off, what a mess.

Cleaned up.

The mess inside.

Cleaned up and ready for new braces.

Gluing in new braces.

Ready to re-glue the back.

Back ready to glue - crack repaired, inside scraped clean.

In place and ready to glue back on.

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Waddy

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Nice recovery Waddy!

Thanks, Robbie! Just lucky, I think.

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Waddy

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Sorry to hear you had problems. For some unknown reason I had a long gap under the center brace too on my third guitar. I fixed by inserting strips of very thin veneer and it worked fine. On my fourth (closed 1 week ago) I've put extra gobars over the braces and it worked fine, although I am seriously considering switching to the "braces glued to the back first" method in the future.

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I have thought about that too, Alex. It would solve the glue, squeeze out issue too. I do like this method though.

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Waddy

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