glueing bone to madasgar rosewood?

[Simon Magennis]

I am makng a madagascar rosewood bridge. I want to glue a flat piece of bone on the tie block. What would you recommend? I have tried 3 times with CR and it failed. IN the first case it seem to grip well enough but I had to removed it as it was skewed. I planed the old glue off the tie block and sanded to bone. Twice in a row it was so weekly bonded that it came away very easily. I tested the CR by gluing two random bits of wood together. I will try with hot glue later.

This has got me worrying about glueing the bridge to the top as well. Searching the forum I say an old comment of my own about madagascar rosewood bridges popping. In the post I said I wouldn't use m.r. again for ridges …

Any special tricks with m.r. and bone or m.r. and spruce .. I do the usual stuff like scraping the wood surface with a razor blade just before glueing, wiping off the oils with a solvent, making sure the surfaces are flat ...

[Christ Kacoyannakis]

Smith Epoxy is specially formulated for oily woods. I believe it is a bit thinner and will soak into the pores of the wood better to create a better bond with the wood. Of course, as you are already doing, wiping off the surface oils with acetone right before glue up will also help.

[Randy Roberts]

As much as I hate to see this battle start again, I can't help myself.

There are many builders who argue against trying to clean the surface with solvents..

If contaminating resins/ oils are soluable in the solvent you use, and so could in theory be "cleaned" off the gluing surface, then the solvent will also soak to some depth into the wood, dissolving those deeper resins/oils also.
As the solvent evaporates from the surface of the wood, the dissolved resins/oils are drawn up to the surface with the solvent, and as the solvent evaporates the resins/oils are left behind on the surface. At best you are just smearing resin around and drawing more to the surface.
Short of somehow soaking the wood in sequential baths for long enough to have pulled out and poured out with solvent changes all the resins/oils present in the wood, you aren't accomplishing what you're trying to accomplish.

You will be best served by creating as nearly perfect fit as you can, lightly scrape the gluing surfaces (not "Scoring" the surface!) and immediately glue with hot hide glue (I've only ever used 192 gram strength HHG but some recommend 351 gram strength for bridges)before the surface of the newly scraped wood has time to oxidize (bind oxygen molecules). Or as Al Carruth visualizes it, before it loses it's surface energy. Glue it within 15 minutes of scraping.

I've only used Brazilian Rosewood for bridges, and have used Cocobolo, Brazilian and Honduran rosewood for back and sides and have not had a glue failure by following these steps.

[Clay Schaeffer]

Something I have done in the past for cocobolo is use full strength dish detergent to pull the oils out. I don't do it for gluing purposes but rather so it retains some of the color fresh cut wood has and to slow the coloring it eventually fades to (mixed success). I thoroughly rinse it with water and let it dry. It washes out most of the color and raises the grain, but a light scraping with a razor blade takes care of that. I've never done it specifically for gluing purposes, but it seems like it might be a better option than a solvent wash.
I have glued cocobolo bridges successfully using the normal procedures of fitting and scraping just prior to glue up. The small amount of madagascar I have seems less oily than coco, and more like BRW, so I would think it would be less problematic when gluing.
Not all CA glues are the same. There are a number of different formulations which react differently with different materials. You could try a different brand of CA. CA also reacts differently as it ages - it becomes thicker and is slower to set up. One thing you might try is "dusting" the bone with baking soda and also lightly dampening the wood tie block area just before gluing. Put the CA on the wood and bring the baking soda dusted bone surface to it. Moisture and baking soda both accelerate the reaction time of CA.

[David King]

Loctite sells many use specific formulations of high strength CA glue albeit at high prices and short shelf lives.
I've heard that bone in particular is well suited to hide glue so I'd certainly start with that combination. The original CA glues were designed to be compatible with oily surfaces and moisture so I've found them to be effective with cocobolo and they tend to cure almost instantly which tells me that cocobolo is tending towards basic/ non acidic.

[Simon Magennis]

In the end I went back to basics. I related each step of the prep and glued with hot animal glue. Seems to have worked fine. Bridge and bone safely on a new guitar and still holding up.