What glue for cocobolo??

[Quinny]

Hi,

I am making a uke with cocobolo back, sides and fretboard. I have read that it is advisable to use acetone to remove resin/oils before gluing with PVA wood glue.

Is that the same with epoxy - that you should rub acetone beforehand??
If you don't need to rub acetone, is it alright to use epoxy for all gluing in the build to get a better bond?

Thanks in advance

Andrew

[kiwigeo]

Hi,

I am making a uke with cocobolo back, sides and fretboard. I have read that it is advisable to use acetone to remove resin/oils before gluing with PVA wood glue.

Is that the same with epoxy - that you should rub acetone beforehand??
If you don't need to rub acetone, is it alright to use epoxy for all gluing in the build to get a better bond?

Thanks in advance

Andrew

I generally give any oily woods a wipe with meths or acetone prior to glue up regardless of glue type. From my experience Titebond AR glue is actually good on oily woods without such preparation but I do it because it only takes a few seconds.

Epoxy glue......I only use it where I don't want any moisture in the joint (eg fretboard/neck, rosette and other inlays). For back/side/top joints I use AR glue.....easier to clean up and also easier to undo the joint should repairs be necessary down the track. For joints with a high chance of needing to be undone I use hide glue. Hide glue is also easier to clean up than other glues.

[56nortondomy]

I've used coco on 3 guitars, the 1st one I glued the backs together with titebond, I possibly didn't wipe them with the acetone good enough because they just peeled apart, since then I've used epoxy and haven't had a problem ( I still clean with acetone first ). For braces and kerfing I use titebond, but I make sure I give it a good wipe with the acetone.
Wayne

[Bob Connor]

Building this Cocobolo guitar at the moment.

Used Titebond on a fresh joint.

Regards

[Quinny]

Thanks Martin, Wayne, Bob.

Wayne, like you I used Titebond to join the back halves. I thinned to 2mm on the drum sander. Then got excited so I wiped it with a wet rag to see the colour and found 5cm of the joining had come undone - must have dissolved the PVA on the edge. I used epoxy to re-fix. At least AI know it is wroth good prep and using mainly epoxy rather than risking glue failures.

Thanks guys.

[demonx]

Cocobolo, use epoxy.

Titebond "could" work sometimes, epoxy "will" work.

Attached pic I used Cocobolo for the top, board and binding. Epoxy as adhesive, no issues.

[mooshalah]

Hi all.

This isn't going to help anyone, in terms of supplying a definitive answer to the question, but rather it's a note to say that I sympathize, and share your pain!

I've been trying to glue spruce braces onto a Cocobolo back. Because I've heard that this can be a problem, I asked an experienced luthier (who in fact sold me the Cocobolo) what he did, and his reply was that he used epoxy, and didn't ever have a problem. I asked him about whether he used any solvents to remove oils, and his comment was that he had never had a problem with epoxy and oil, and that in his opinion, leaving the oils on/in the wood gave a more complex, interesting finished appearance over time.

I had already used Titebond to join the two halves of the back, and this bond seemed quite acceptable, but I thought that perhaps I had still better take the advice I'd been given, regarding the braces.

I thought I might hedge my bets, and wiped the wood with acetone in the regions where the braces were to be adhered. I was immediately struck by how dark and dirty the cloths (and spruce back-graft!) that I used for this purpose became. I kept on wiping until no further oil/dirt/colour/material appeared on the cloth, and then proceeded to mix the epoxy (well), apply it to the braces, and squeeze them down in my usual go-bar deck. The first thing I noticed was that (as one would expect) the adhesive didn't "grab" so that I had to hold each brace firmly in place, by hand, until it had stopped slipping 'round - maybe 10 - 20 seconds. The second thing was that as the epoxy squeezed out, it didn't present as discrete beads, as is the case with Titebond, and I reckoned - and this proved to be the case - that clean-up was going to be quite a bit more difficult than with Titebond. (Everything had equilibrated at around 45% RH for a few days)

After leaving everything for around two days, I removed the back from the go-bar deck. The day after this (yesterday) I proceeded to clean up, and (only) one of the braces came away easily from the back; the joint failed spectacularly, in that I was able to "peel away" the Spruce brace from the Cocobolo in one go, without in any way damaging either the brace or the back. It was clear that the epoxy had not adhered to the Cocobolo. All the (now hard, almost glassy) epoxy was strongly stuck to the brace, while leaving virtually no residue on the Cocobolo.

In fact, there was some adhesion left along the squeeze-out line, which proved a little more difficult to remove, than the few, easily peelable flakes where the brace had been. This made me consider that perhaps too much clamping force might have been applied, that insufficient epoxy had remained, and that the joint had been "starved".

Of course, I'm now left with a number of conundrums (conundra?);

1/. The other braces seem to be holding strongly; but shall I remove them anyway? (If one doesn't know the source of a error, one is probably destined to repeat it.)
2/. Shall I just forget it and use epoxy again, or shall I use Titebond on this brace? (And with or without application of solvent - naphtha, acetone, Shellite, methylated spirits or even acetone?? My chemist's head spins with thoughts of polar v/s non-polar solvents!)
3/. What should I do when it's time to adhere the back to the sides and linings (and bindings)?

There it is. I find that under such circumstances my brain tends to switch off and I adopt the "Huh! That's strange; I dunno. Gee, I guess I'll just ignore it - pretend it didn't happen - assume that everything's fine and normal, and it'll never happen again" approach (otherwise known as silicaceous cranial interment).

Frank.

[demonx]

Frank:

I very rarely use acetone or similar to clean wood prior to glue up, I prefer a fresh sanded and airhosed surface.

One thing to keep in mind is, any contaminate on the surface stops the paint or glue from adhering.

I often see people wipe on all sorts of things to see how "pretty" a piece of wood might look when finished. I see this as potential contamination and avoid it. I often see sales people do the same, which you often don't know what they have put on.

If you've wiped acetone over a water resistant timber like Cocobolo, it won't absorb, it will still evaporate, however even though you may wipe it off there will still be residue. I'm guessing a its a normal garden variety acetone so it's probably got some dirty or oily contaminates in it as opposed to an expensive laboratory grade, so my guess is when you've tried to clean it, you've made it worse.

I mention airhosing, as when you pull it out of the drum sander, all the pores will be filled with dust, quite often pressed in from the drum. This can also cause the glue to fail. I've never had it happen, but it could as its not a "clean" surface area.

[blackalex1952]

I think the word is " conundrums". It is possible that Conundra is a place in Queensland...the people of Conundra are confused...

[mooshalah]

HI DEMONX.

THANKS FOR THE REPLY, AND FOR STUFF WORTH THINKING ABOUT. MY BRIEF RESPONSES ARE IN CAPITALS (SORRY FOLKS, I'M NOT "SHOUTING"; JUST TRYING TO BE CLEAR WITHIN THE BODY OF SOMEONE ELSE'S MESSAGE)

Frank:

I very rarely use acetone or similar to clean wood prior to glue up, I prefer a fresh sanded and airhosed surface.

One thing to keep in mind is, any contaminate on the surface stops the paint or glue from adhering.

I often see people wipe on all sorts of things to see how "pretty" a piece of wood might look when finished. I see this as potential contamination and avoid it. I often see sales people do the same, which you often don't know what they have put on.

YEP; VERY TRUE. AND IF SOMEONE USES SOMETHING LIKE TURPENTINE OR LINSEED OIL, THEN IT CAN BE A WORLD OF TROUBLE DOWN THE TRACK. ONE HAS TO ADD THE CONCEPTS OF HYDROPHILICITY AND HYDROPHOBICITY (!!) INTO THE MIX - BASICALLY, THAT OIL AND WATER (OR THINGS WITH SURFACES SIMILAR TO THESE, DON'T MIX) - WHICH IS WHY EVEN THE SLIGHTEST AMOUNT OF SILICONE OIL ON WOOD PREVENTS FINISHES FROM ADHERING.

If you've wiped acetone over a water resistant timber like Cocobolo, it won't absorb, it will still evaporate, however even though you may wipe it off there will still be residue. I'm guessing a its a normal garden variety acetone so it's probably got some dirty or oily contaminates in it as opposed to an expensive laboratory grade, so my guess is when you've tried to clean it, you've made it worse.

SORT-OF TRUE. THE "GARDEN VARIETY" OF ACETONE PURCHASED FROM SAY BUNNINGS IS GOING TO BE ESSENTIALLY PURE (97 - 100%), WITHOUT OIL. BUT OF COURSE, "OILY ACETONE" BOUGHT IN A PHARMACY FOR REMOVING NAIL POLISH IS AN ABSOLUTE NO-NO.

I mention airhosing, as when you pull it out of the drum sander, all the pores will be filled with dust, quite often pressed in from the drum. This can also cause the glue to fail. I've never had it happen, but it could as its not a "clean" surface area.

THIS SOUNDS LIKE A REALLY GOOD POINT.

THANKS,

FRANK

[Quinny]

Ok. things are getting a little confusing. I think I will do some tests on off cuts with my cocobolo and test glue bracing, kerfting and to the cocobolo itself - plus and minus acetone cleanup. My test results will simply be if i can add a fair pull on the peices without failure - unless of course a piece doesn;t take at all. Stay tuned.

Andrew

[mooshalah]

Hi Andrew.

Yes, we seem only to be muddying the water. Sorry.

I resanded the cocobolo in the place where the brace was to go, and cleaned and reglued the brace that sheared off, with Titebond. I wiped the area where the brace was to be reglued with acetone (on the basis that I just couldn't see how this would hurt) and this time the brace seems to be rock-solid.

The take-home message for me personally is that I shouldn't attempt to stray too far from what I know to have worked in the past (acetone and Titebond on "oily" woods).

My ruminations and rationalizations for all of this are that:

Titebond Original is a water-based adhesive (water compatible aliphatic resins emulsified in water), and when it is applied and sets, it both keys within the (microscopically) porous cellulose and lignin surface of the wood, and chemically bonds with compatible elements within the wood structure;

Titebond and wood - all wood, presumably - are compatible. While Cocobolo - like all woods - has moisture within it, and hence can and should bond with Titebond, the presence of hydrophobic (water repelling) oils disrupts this process. This oil can be removed by dissolving and wiping it from (and from just below) the surface about to be glued, with a cloth soaked in a suitable solvent. Suitable solvents are any that dissolve and remove the oil, don't impart anything to the wood, and evaporate quickly. To the extent that different woods might have different extractibles, one solvent might work better for one wood than another.

The reason we are cautioned to fairly quickly glue such wiped surfaces is that there is still oil within the wood, and that it will migrate to the surface that we've just wiped (like, it sees an oil-less "gap" above it, and rushes up to fill it). I dunno how long this takes, so I tend to follow the "quicker the better" rule!

I think that Demonx makes a good point with regard to removing sanding dust, and I'd expand on this just a little by saying that it's understandable that there might be keying problems with close-grained, dense woods like Cocobolo. In particular, planed, rather than sanded surfaces seem to present a problem because of the lack of keying sites. Since adhesion is both a keying (squeezing into pores) and chemical bonding with surfaces, while it's good to to sand (roughen) the surface to make more "pores" available for keying, dust from the sanding process might actually fill these desirable "roughnesses", and prevent good adhesion. Thus, thorough removal is a logical good idea.

It occurs to me that if one uses a glue like an epoxy that is non-water-based and hence possibly more lipophilic (oil loving) than Titebond, removal of oil from the surface of the Cocobolo might actually cause adhesion to fail. If any chemical bonding occurs between the epoxy and the wood, this is most probably a different set of reactions than between Titebond and wood, and the absence of oil (in a microscopically small environment) could prevent good bonding! Perhaps that's why my attempt at using acetone to remove oil and then gluing with epoxy failed so spectacularly!

Of course, Andrew, one of the greatest criticisms of ancient Greek science, was that they thought they could think everything through; that it was somehow unseemly to dirty their hands, actually doing experiments! So I think that your approach, of actually doing something, is going to be the most useful of all.

Regards,

Frank.

[Quinny]

Thanks Frank for your frank and detailed reply!

I need to say that my cocobolo has been sitting at my home for probably a year or more. I had another forum member (gratiously) thin the sides a year ago and it left a huge amount of resin on his drum sanding paper. Yet when I drum sanded the back pieces now - a year later - I got no oily residue on my sand paper at all. So i think that is one big factor.

One year on and having conducted my experiment the results are in. I had variables as follows:
- I glued brace wood to cocobolo and the cocobolo to itself
- With acetome wiped surface versus no acetone wiping at all
- comparing titebond to epoxy.

Results: with 16 glue setups they all stuck ruddy well. I couldn;t remove any by hand. Then whey I got a screw driver onto the wood I just damaged the wood, no give at all - whether i used acetone first or not, or whather i used epoxy or titebond - to the brace wood or cocobolo to itself.

So I suspect is that it is worth letting the cocobiolo dry enough. It may be a separete issue to glue wet and resinous cocobolo. My pieces seem to have dried enough. Having tested my actual pieces I can proceed with confidence.

Thanks guys for getting my grey cells working.

Andrew

[TKAY]

Don't forget to have Filters/dryers on the outlet of the air supply. It may come as a surprise to see what is in the air if directed at a shiny surface or pane of glass.
Don't forget to drain the air tank frequently, particularly in humid areas.
Tom