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Gluing Oily Cocobolo
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=33957		 Page 1 of 1
Author:  Steve Frady [ Thu Oct 20, 2011 7:57 am ]
Post subject:  Gluing Oily Cocobolo
I am thinking about using a Cocobolo fingerboard. I am interested in other peoples experience with gluing this oily wood.
Author:  Corky Long [ Thu Oct 20, 2011 8:25 am ]
Post subject:  Re: Gluing Oily Cocobolo
Some are highly allergic to Cocobolo. (Be careful when resawing,etc.)

One thing that surprised me was, I remember seeing Lawrence Juber walking around the Newport Guitar Festival trying out luthier's guitars. He asked whether the fingerboard was Cocobolo because if it was he wouldn't touch it.

As for gluing it, I've heard that as long as you have a recently planed or scraped joint, you should be okay with the standard glues (Titebond, HHG, etc.).
Author:  Stuart Gort [ Thu Oct 20, 2011 10:39 am ]
Post subject:  Re: Gluing Oily Cocobolo
I use epoxy and prep the fretboard with a light sanding followed by a wipedown/scrub with acetone just prior to gluing (m.e.k. would be fine too). Epoxy has aggressive properties and although other glues will likely work too....epoxy is the best long-term guarantee with an oily wood like cocobolo. I used cocobolo fretboards on my last 10 necks and there's no chance of them delaminating.
Author:  windsurfer [ Thu Oct 20, 2011 11:44 am ]
Post subject:  Re: Gluing Oily Cocobolo
Freshly scraped surfaces glue just fine with hide glue.

My tests showed that a solvent wipe after scraping made the glue joint weaker.

-jd
Author:  Ken Franklin [ Thu Oct 20, 2011 12:07 pm ]
Post subject:  Re: Gluing Oily Cocobolo
windsurfer wrote:
Freshly scraped surfaces glue just fine with hide glue.

My tests showed that a solvent wipe after scraping made the glue joint weaker.

-jd


+1 LMI white works fine too.
Author:  weslewis [ Thu Oct 20, 2011 10:33 pm ]
Post subject:  Re: Gluing Oily Cocobolo
+ 1 on sanding or scraping before gluing, both hide glue and titebond have worked well..
Author:  Tai Fu [ Fri Oct 21, 2011 1:57 am ]
Post subject:  Re: Gluing Oily Cocobolo
I looked at a cocobolo back when I was visiting that luthier in Berlin... I tried smelling the wood because I remember working with a rosewood like wood that smells like chocolate when cut. I thought it was cocobolo but it turned out that just sniffing cocobolo makes me want to sneeze. It's got some irritating stuff in it.

That alone is enough to make me not want to work with it...
Author:  mqbernardo [ Fri Oct 21, 2011 6:06 am ]
Post subject:  Re: Gluing Oily Cocobolo
windsurfer wrote:
Freshly scraped surfaces glue just fine with hide glue.

My tests showed that a solvent wipe after scraping made the glue joint weaker.
Hi! may i ask if it made the joint a lot weaker, or just a tad?

thanks,
miguel.
Author:  DennisK [ Fri Oct 21, 2011 7:23 am ]
Post subject:  Re: Gluing Oily Cocobolo
Tai Fu wrote:
I looked at a cocobolo back when I was visiting that luthier in Berlin... I tried smelling the wood because I remember working with a rosewood like wood that smells like chocolate when cut. I thought it was cocobolo but it turned out that just sniffing cocobolo makes me want to sneeze. It's got some irritating stuff in it.

That alone is enough to make me not want to work with it...

Wow, I guess I'm really not allergic to it (yet). I love the smell. But I do try to avoid breathing the dust, and rinse any off my skin after working with it, in hopes of keeping it that way.

Brazilian is the one that smells like chocolate/talcum powder. Quite possibly the best smell in the world.

Anyway, the extent of my experience with cocobolo is joining one back. I planed and quickly glued with HHG, and it seems to be quite strong. For a fingerboard, I'd give it a light scraping to remove any oil from the surface, and stick 'er down. With such a huge glue area, specks of oil starting to seep out should be no problem. Wiping with solvent runs too much risk of spreading a thin coat over the entire surface.
Author:  windsurfer [ Fri Oct 21, 2011 10:10 am ]
Post subject:  Re: Gluing Oily Cocobolo
mqbernardo wrote:
windsurfer wrote:
Freshly scraped surfaces glue just fine with hide glue.

My tests showed that a solvent wipe after scraping made the glue joint weaker.
Hi! may i ask if it made the joint a lot weaker, or just a tad?

thanks,
miguel.


I glued 1/2" x 1" scraps from a coco fingerboard to a block of mahogany with LMI hide glue. The ones I solvent cleaned sheared off cleanly with a couple of taps from a plane hammer leaving almost no glue residue on the coco surface. Freshly scraped and not solvent cleaned had to be hit with a bigger hammer and tore the mahogany away when they finally failed.

-jd
Author:  Stuart Gort [ Fri Oct 21, 2011 11:20 am ]
Post subject:  Re: Gluing Oily Cocobolo
windsurfer wrote:
Freshly scraped surfaces glue just fine with hide glue.

My tests showed that a solvent wipe after scraping made the glue joint weaker.

-jd


I would clarify.

Using solvent prior to gluing with epoxy will dilute and evenly disperse whatever naturally remaining oil residue exists after sanding. Epoxy, being very aggresive, will create a much better bond over a homogenized, thin layer of release film than an uneven, blotchy layer...and I have to assume that natural oils are not perfectly evenly dipersed throughout a piece of cocbolo in either a macro or a micro sense. I wouldn't presume to speak to what happens with other glues in this situation other than to theorize. I just know the properties of epoxy pretty well...and I would not pick another glue in the presence of any kind of oily release agent.
Author:  Stuart Gort [ Fri Oct 21, 2011 11:25 am ]
Post subject:  Re: Gluing Oily Cocobolo
windsurfer wrote:
My tests showed that a solvent wipe after scraping made the glue joint weaker.


What solvent did you use?

It's entirely possible that your solvent introduced a release residue. It's also possible that evenly dispersing the natural oil of cocobolo works to improve the release characteristics of a bond using hide glue because hide glue won't break down the molecular composition of oil the way epoxy does. But if you're working with an essentially acidic glue it's best to have a thin, even layer of oil to eat through.

We didn't test cocbolo...but we did controlled load cell tests of the bond strengths of numerous types of finishes and laminate bonds with various substrates in my former business. I saw a slight improvement when gluing maple to maple (hard rock) if acetone was used just prior to an epoxy bond. I can only theorize why it happened. So...everything I'm saying about cocobolo is theory without having tested it...except for the necks I've made....and I'm not whacking them with a hammer :) though I did stand on a few of them to test for microcracking. If there was a bond that could be characterized as questionable they would have failed under that load.
Author:  windsurfer [ Mon Oct 24, 2011 11:13 am ]
Post subject:  Re: Gluing Oily Cocobolo
I got the same results with Acetone and Methonol. Likely the solvent is drawing oil from the pores and recontaminating the surface, preventing proper wetting by the glue.

As you are aware epoxy is a completely different animal than hide glue. The biggest problem with epoxies and oily woods is that the oil can dissolve in the resin and inhibit full curing.

-jd
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