Disassembly of a glued joint-folklore?

Re: Disassembly of a glued joint-folklore?

Bruce, a MN Galoot

>I've heard that vinegar would hasten the demise of a PVA joint, but I didn't know that steam would work. I suspect that the steam used in cleaning furniture factory clamping stations is probably higher pressure and more saturated than steam available to the home user. Steam can be dangerous stuff.

OTOH, I have disassembled hide glue joints with little difficulty, just hot water and reverse clamping pressure. It's just a little scary how easily they came apart. But I sure appreciated the ease of disassembly. I've never been able to get a PVA joint apart without destroying something in the process.

Bruce

details?

bill tindall

>Did you soak the joint(wood) in hot water-minutes, hours? For example, suppose I wanted to disassemble a M&T frame. How would the joints be treated? Submersion in hot water? It is not clear how you got the hot water to the glue? And did I understand correctly that a similar treatment did not soften yellow glue, thereby validating the difference?

One key difference: Reassembly

Mike Recchione

>One very nice thing about hide glue joints is that you can not only take them apart, you can put them back together without going back to bare wood. What I've done is to get the excess off with hot water on a rag, and then just apply new hot glue. It combines with the old glue to give a joint that's as good as the original. So, for things like musical instruments, where you may need to take them apart and put them together multiple times, it's still probably the best way to go. I've done this for a chair I was repairing as well as a guitar, and it worked very well both times.

One advantage... *LINK*

David Barnett - Venice, Florida

>...as Adam Cherubini points out in "Chair Restoration -- Hide Glue", is that hide glue can be reactivated, making it easy to reglue a loose joint without having to scrape (or worse) the surfaces free of aliphatics, such as Titebond, or build the surfaces to a tight pressure fit. For some applications, hide glue's reversibility is critical. Luthiers, for example, must take apart and reassemble very old and valuable stringed instruments, and only hide glue makes this possible year after year. Knox brand gelatin's great for this, by the way, and comes in handy packets.


Chair Restoration -- Hide Glue

Re: details?

William Duffield, on the Cohansey

>I dump out the cold coffee, refill the coffee cup with water, nuke it to boiling, take the cup back to the bench, and apply hot water to the surface of the joint with an acid brush. It wicks right in, the hide glue soaks it up and softens. Usually, by the time I've applied it to several joints, the first joint is soft enough to start to move.

Martin guitars vs. furniture

john jesseph

>I suspect this refers to getting the necks of Martin-style guitars. I have not done this, but is is common practice to remove the fifteenth fret and drill a small hole to let in steam. There is no better access to the joint, based on the relationship of the back, sides, and fingerboard. This is another example of something not originally designed to come apart- not nearly as simple and elegant as a violin. There is a lot of online violin forum discussion about cussing people for using pva etc. glue as Mike R. said, as much for regluing as much as dissassembly.

Mortise and tenon is pretty straightforward, and the chances of ruining the object is not as high as a guitar.

just exactly what Sir William said.

Bruce, a MN Galoot

>

Re: Disassembly of a glued joint-folklore?

Todd Stock

>Fisrt - we are talking hot hide glue, versus the stuff in a bottle that is pretty much good only for non-structural applications such as glue size, etc.

My assumption is that you're asking if - in the event of a partial glue line or partial tenon failure in a M&T joint - which adhesive offers an easier repair. I'd say hide glue, with some reservations on where it is used.

Hide glue will reactivate in water - the addition of heat speeds the process, but the key ingredient is water. Soak the joint with warm water, and eventually, the hide glue will liquify. Add some fresh glue to amagamate with the reactivated old stuff and clamp.

TB (TB 1) will take longer to soften, and cannot be reactivated - it's got to be removed down to the wood surfaces in the joint prior to regluing. TB II/III are both going to require lots of heat to soften the glue line becuse they are water resistant (and TB III is actually pretty resistant to temps under 212 degrees F), so in this case, steam is used to transfer the heat energy involved in the phase change from vapor to liquid to the wood. You could transfer the same amount of heat by wrapping the joint with the silicon filament heating bankets used by luthiers to remove bridges, fingerboards, etc.; however, chances are good that this would toast the finish around the joint as well, so not a great solution.

FWIW, the reason why the procedure for guitar neck removal is identical for TB and hide glue is that the dovetail is shorter than the socket, creating an air space under the 13th or 15th fret (12 fret or 14th join to body, respectively). This space traps both the steam and liquid water, creating lots of heat (to soften the TB), and trapping moisture (to liquify the hide glue and further desolve the TB).

The only problem with leaving space between the tenon and back mortise wall - say in a joined chair - as a feature to ease future repairs is that the tenon length versus mortise depth really needs to be known by the repair guy to make things work. Some cabinet makers provide wood/finish/glue type info to their customers, but it's unlikely that the as-built plans will be included as well.

To further complicate the choices, TB (all formulations) is more shock absorbant than instrument/general woodworking grade (gram strength) hot hide glue, so there are some good reasons to use AR glues in furniture that gets slammed around. One of the reasons why I use a harder drying clear version of TB from one of the luthiery suppliers is that it is almost as hard as dry hide glue, but remains a little more shock tolerant. I also have gone back to TB 1 for furniture construction.

Picture did not work *LINK*

Dan Donaldson

>You posted the link to the html index page rather than to an image. If you are posting an image, it has to end in .jpg or .gif and be the link to the actual image. I am posting the url you used as a link.


Guitar neck picture index.

Re: A better link *LINK*

William Duffield, on the Cohansey

>If you back up to the parent directory, you find an HTML file with thumbnails and links to all the big pictures. But, none of them show removing the fret, drilling the hole, or injecting steam.


A 1974 D-28's New Neck

Re: Disassembly of a glued joint-folklore?

Adam Cherubini

>BILL,

You asked for experience and mine is limited:

I had great trouble removing/reversing recently glued hide glue joints where the joint was sloppy to begin with. I was using straight glue, no additives of a moderately low gram strength (I buy 192 from Joel but it degrades (or so I'm told) with repeated heatings). When I say "trouble" I mean "failure". I broke the parts.

In tight fitting joints on the same piece of furniture, reversal was no problem. It appearing that very little glue was in the joint.

I've taken apart rub joint glue blocks, installed cross grain. I applied hot water, waited seconds, then struck said glue block with my favorite patternmaker's warrington hammer (I want to make sure you have all the details, Bill). Clearly the water reversed the glue since the blocks came right off cleanly. I should mention that I also sang an Olde English work song before striking the glue blocks which probably had the same effect as the hot water on reversing the glue. I suspect others have sung this same tune to achieve similar results (and similarly correctly attributed the result to the combination of the chemical and meta-psycho reaction).

Here's my w.a.g.:

In a tight and craftsmanly M&T joint (I know you are all planing your tenon cheeks smooth with your new LV shoulder planes- I wonder if LV will make a cheek plane soon?), the hide glued joint will be easier to remove than the PVA glued joint. Hide glue extrudes out of piston fit joints like these. On a loose fitting joint, the PVA will be easier to dissassemble because M&T really can't be clamped and PVA just won't develop properties over a significant gap. Conversely, that same sloppy joint may well be next to impossible to disassemble if hide glue is used.

Moxon said craftsmen added beer to their glue pots to give it strength. Alcohol would break the inter molecular bonds and weaken the glue. Almost anything you add weakens the glue. Our experience reversing old joints may be predicated on the poor quality of the old glue. Salts added to hide glue slow the kick time and weaken the glue, but they also make hide glue more hydroscopic which makes it even easier to reverse (double whammy- low bond strength and hydroscopicality- (okay I made that word up)).

Adam

Re: A better link

john jesseph

>I had a couple more minutes to get the link to work... I was just attempting to illustrate how difficult it is to access the joint without damaging anything or making a complete mess of the lacquer finish. The hole is at through the fretboard near the neck of the dovetail, in the mid-lower left of the pic. Long run for a short slide!

Hit him in the face with a pie....

john jesseph

>

Re: Disassembly of a glued joint-folklore?

Bruce, a MN Galoot

>what kind of TB do you get and from what luthierie?

Bruce

And would that TB be suitable for

Bruce, a MN Galoot

>a soundboard or back? Or only structural joints?

Bruce

old glue

Warren in Lancaster, PA

>Hide glue gets harder and more brittle as it ages. A joint that was not glued recently can easily be knocked apart without heat or water. A recent joint is much more trouble to take apart.

Re: old glue

Adam Cherubini

>I like my beer story better.

HI WARREN!

Adam

Re: old glue

Todd Stock

>The advantage of hide glue in instrument making is the ability to transfer vibration across the glue line with very little loss, so it stands to reason that it would be a bit less shock resistant that softer glues such as TB II/TBIII.

Martin still builds nearly all their guitars with TB I since moving from their old factory (steam heat...lots of warm, perfectly humidified air) to newer factory-like digs with drafts that routinely gelled the hide glue before componenets could be assembled.

Interestingly enough, Martin is selling an 'authentic' version of their 1937 D-18 mahogany dreadnaught, built with original materials, inlay, and *you guessed it...* hot hide glue. Street priced about where custom luthiers sell their best work, but like a LN LA Jack, still less than what the originals are running.

Re: And would that TB be suitable for

Todd Stock

>The AR I use is LMI's instrument maker's glue, which drys clear (no dyes), seems to be harder than TB 1 and much harder than TB II/III. Not cheap at $8/bottle, but 8 oz container looks like it will last through 4-5 guitars.

Re: where to use hide glue, I have not yet developed the necessary technique for gluing top/back to ribs in the limited time available - I've done a couple of trials, and I'm still slower than the glue. In any event, the top and back braces probably benefit most from using hide glue, so my current approach is hot hide for braces and LMI's version of TB (AR glue, generically) for closing the box.

Another great thing about the LMI stuff is that it appears to work well with ebony, rosewood, etc. - I use it for bridge and fingerboard extension as well.

I'm about to venture into my first guitar

Bruce, a MN Galoot

>which actually seems like a handtool users delight! However, I'm not going to glue the neck to the body. I think I'm going to use the Cumpiano bolt method instead. I did a couple hourglass dulcimers as warmups, and they turned out pretty well. What the heck...

I had strong reservations about using hide glue to glue on the back and top because of the time factor. I'm just not that fast, so I really appreciate the reference to LMI's glue.

On her site, Kathy Matsushita talks about using Titebond. Do you know which variety she uses? Maybe I should just email her.

Thanks again.

Bruce

creep, reversibility, and titebond

john jesseph

>Haven't all these topics been covered here? I have goofed around with LMI glue, but have not used it for anything substantial- still using hide glue. I am thinking about trying to use it for everything unless I can find a good reason not to. Gotten further with fiddle and mandolin construction, waiting for the day to come when I can focus on a steel string guitar...

Re: I'm about to venture into my first guitar

Todd Stock

>Official Luthier's Forum. Register, announce you are a newbie, and start shooting questions...sort of like this place, but fixated on guitars.

Also - Musical Instrument Maker's Forum (MIMF) has a library (register to gain access) that has stuff on just about anything related to guitar making. They have an entire section devoted to adhesives. Spend a few hours tooling around the site.

In any case, you can't go wrong with TB I (don't even think about using TBII, and the jury is still out on TB III) or better yet, the LMI instrument makers glue.

Good luck!

Re: creep, reversibility, and titebond

Todd Stock

>The LMI AR and TB I don't seem to exhibit creep at normal temps. I glue bridges with LMI and that's one of the first places I'd expect creep. TB II definitely has some issues with creep, and TB III appears to share some characteristics.

If I thought I could do an entire instrument with hide glue, I'd go for it; however, with 30 inches of 3/8" wide lining to do, it's tough to ensure a perfect glue line.

many, many thanks!!

Bruce, a MN Galoot

>