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| Gluing up Cocobolo? Concensus? http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10102&t=14766 |
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| Author: | j.Brown [ Sat Dec 01, 2007 4:57 pm ] |
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I've done some searching of the archives here and have done some digging around elsewhere, but I'm wondering if there was ever a consensus on the gluing up of cocobolo? how to treat the wood (scrape vs. chemicals), which glue to use, etc. -j. |
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| Author: | Rick Turner [ Sat Dec 01, 2007 5:36 pm ] |
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Napalm works great on the stuff... Oh, sorry, that's South Asian rosewood that it works on... Seriously, we acetone wipe and then use epoxy for center seams, and acetone wipe and use LMI white or HHG for anything else. |
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| Author: | Howard Klepper [ Sat Dec 01, 2007 5:48 pm ] |
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I've had good results wiping with acetone, and good results with a freshly prepared (preferably scraped) surface and no wipe. By fresh I mean within minutes of gluing. It's not a big deal. |
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| Author: | TonyFrancis [ Sat Dec 01, 2007 8:57 pm ] |
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No solvents here. A higher gram strength hide glue holds far better on this resinous wood (we use it all the time for rope marqueterie). The lower grades arent so flash. No epoxy or titebond experience so best of luck there. |
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| Author: | Hesh [ Sun Dec 02, 2007 12:28 am ] |
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There was another thread on this, I think it was in the last 3 months and it was pretty good. I searched for you but could not find it. Perhaps someone else can find it and post a link? |
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| Author: | JJ Donohue [ Sun Dec 02, 2007 12:37 am ] |
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I seem to remember that thread...and that the consensus seemed to favor scraping over solvent wipe and that a few had some bad results after using acetone. My notes say...use scraping and epoxy...no acetone. OK...Now I'm ready to be caught in the crossfire as soon as the west coast awakens! 
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| Author: | GregG [ Sun Dec 02, 2007 12:48 am ] |
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I recently glued up some cocobolo back plates with titebond, within a minute of jointing the edges, the next day I was inspecting the joint putting a little pressure/flexing it and shazam....the seam just unzipped like it was held together with tape, not good! I then cleaned everything up and glued with West epoxy, solid as a rock now! Greg |
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| Author: | LanceK [ Sun Dec 02, 2007 1:32 am ] |
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West system and a fresh preped joint for me, also for the back braces. I -always- try to break the seam on the cut offs after cutting out the back, and sofar it has NEVER broken on the epoxied joint, always next to it. |
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| Author: | Dean [ Sun Dec 02, 2007 1:49 am ] |
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West Systems has a new blend just for oily tropical woods, probably a special order from your dealer. Dean |
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| Author: | grumpy [ Sun Dec 02, 2007 3:03 am ] |
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I build more coco guitars than any other wood. So far, polyurethane for the center joint, HHG for everything else. I've only ever had one failure: that was the first time I had used the acetone wipe. I re-did that joint without the acetone wiping, after jointing it again, and it's held perfectly since. If there's a key that I found also, it's what Howard said; fresh! Scrape or plane and glue right away. When I wiped with acetone, it seemed to pull the oils to the surface instantly, and no amount of wiping would improve; perhaps this was a very oily piece, but it's proven to me that a clean, fresh joint holds perfectly fine... So, i just forget that it's cocobolo, and use it like any other rosewood.... |
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| Author: | Don Williams [ Sun Dec 02, 2007 3:35 am ] |
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Any reason why cooking a coco back wouldn't help with the oil and resins? I've also heard using Smith's epoxy is great because it's made specifically for oil/resinous woods. I'm betting the Poly glue will work great as Mario suggests. My experience with it so far has been very good. It cures really hard, and as long as it isn't prone to creeping...well, it could be a perfect glue for coco. |
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| Author: | LanceK [ Sun Dec 02, 2007 4:03 am ] |
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Don, when we bend the sides, we are cooking them, the resins pour out! I think baking the back is a great idea and the same thing would happen. I have said this before, A well know and respected Luthier that will remain nameless out of respect told me directly, that if you bake your Cocobolo backs you can glue them with Elmer's if you so choose. |
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| Author: | grumpy [ Sun Dec 02, 2007 4:34 am ] |
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trust me when I say, polyurethane glues don't creep. I have tried, and tried, and tried to make 'em creep. If it was reversible, it would be the idea instrument glue. Honest! |
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| Author: | Don Williams [ Sun Dec 02, 2007 5:12 am ] |
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Well, then let it be so noted! No creep! |
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| Author: | Shawn [ Sun Dec 02, 2007 5:49 am ] |
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I agree with Rick...for resinous Cocobolo you can not go wrong with acetone and then epoxy. I have used HHG and other methods in the past but have never been let down when using epoxy after wiping with acetone. I did have one back seam open in the past with acetone and LMI white glue so have done epoxy since. |
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| Author: | Daniel M [ Sun Dec 02, 2007 6:00 am ] |
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I have only built two Cocobolo guitars but I got a fair amount of experience with gluing the stuff in that short time. javascript:AddSmileyIcon('  ')
The upshot of what I learned is that no mater which glue I used, it wouldn't hold reliably if I didn't scrape or sand the wood & wipe the joint repeatedly with an aggressive solvent. I tried both acetone & lacquer thinners & found (in this admittedly meager test sample) the lacquer thinners worked best. Both guitars were built at the same time & the first was put together with polyurethane & all the joints held together fine. On the second, I used poly again on the kerfed linings & was able to pry them off fairly easily by hand. Just for "fun" I scraped the surfaces again, washed really well with lacquer thinners & tried titebond. Worked great. I have another coco guitar in the works, so this is a timely thread. I think the polyurethane worked best, but it's a bit messy & I ended up with shiny glue lines visible on the back, at the edges of the braces. I didn't like cleaning the poly foam from the kerfs in the linings either. Solid linings if I use the stuff again. |
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| Author: | Howard Klepper [ Sun Dec 02, 2007 6:23 am ] |
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A comment FWIW on using polyurethane and wiping with acetone: Mario had a failure with this method. I have a lot of faith that there was no other issue such as badly jointed surfaces, stale glue, etc., because, hey, it was Mario. But this single incident has been mentioned over and over again by people on MIMF until it has become the common wisdom there that there is irrefutable proof that acetone wipe is a bad thing to do with cocobolo. This from the failure of a single joint. I have what I think is a plausible explanation for Mario's failed joint: polyurethane requires a certain amount of water content in the wood at the joining surface in order for it to bond and solidify. Acetone (as folks who took an organic chemistry lab may recall) joins with water on a molecular level and evaporates away taking the water with it. That's why it's used as a rinse to dry glassware in the chem lab. So my conjecture is that an acetone wipe dries out the wood enough that it can cause a polyurethane glue joint to fail. |
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| Author: | Rick Turner [ Sun Dec 02, 2007 6:30 am ] |
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Howard, you belong in a new CSI series... Howard Klepper, FL...Forensic Luthier, that is... |
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| Author: | TonyFrancis [ Sun Dec 02, 2007 7:17 am ] |
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Guitars made with epoxy? You guys are mad. |
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| Author: | grumpy [ Sun Dec 02, 2007 7:35 am ] |
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Acetone is also a fast evaporative, and thus was long gone before I wiped with the moist towel before I apply the glue. nice storyline, though <g> I understand the issue with the 1 of 1 of my non-support for acetone wiping, but it's backs with dozens of otherwise perfectly solid joints. And while others have had success with the acetone wipe, if we had a choice, and I'm suggesting to everyone a time proven choice here, would we really rather -not- stand there wiping the wood with acetone/MEK/lacquer thinner? Especially if, if nothing else, it's completely unnecessary? Who came up with this "we must wipe down cocobolo with a strong solvent" idea, anyway? And what adhesive9s) were -they- using? |
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| Author: | Grant Goltz [ Sun Dec 02, 2007 7:46 am ] |
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Well, I just do my cocobolo gluing just like any other wood and I use Elmer's Carpenters Wood Glue and it works just fine. I don't wipe, I don't scrape, I just build and all is fine. As for the polyurethane glue, in the Fine Woodworking Magazine tests, the polyurethane was the weakest glue, especially on dense tropical hardwoods. So how do we figure all of this out 
Grant |
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| Author: | grumpy [ Sun Dec 02, 2007 8:20 am ] |
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They didn't clamp in that test.... the whole thing was a crock <g> Use some, and make up your own conclusions. |
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| Author: | Howard Klepper [ Sun Dec 02, 2007 8:34 am ] |
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Hmmm . . . Mario, the first time I asked you about this a couple of years ago, I thought you said you didn't do the damp towel wipe before gluing. Any chance you are remembering differently now? |
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| Author: | Hesh [ Sun Dec 02, 2007 8:48 am ] |
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Ah yes.... to wipe or not to wipe - probably depends on if you live alone, or, wish to........... |
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| Author: | grumpy [ Sun Dec 02, 2007 9:23 am ] |
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Hmmm, no, I don't recall saying that. Maybe I said it wasn't dripping wet like Norm Abram does, but I've always used a damp rag/paper towel. |
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