Using colored sawdust + CA glue to create an "inlay" in ebony

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RunnerVince

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I'm doing a project with some ebony where I've carved in a diamond pattern into the ebony, and my initial plan was to fill the carved areas with bloodwood sawdust and CA glue. This has thus far proved unsuccessful. The glue doesn't seem to want to adhere to the ebony. I'm planning on spending some more time trying a few different approached, but I wondered if you fine folks might have any ideas on how to proceed.

I think any solution is going to require undercutting the carving first, so I'm going to start with that, and maybe taking a scrap of the bloodwood to my sander to get some finer sawdust. If that doesn't work, I'm out of ideas.

Thanks everyone.
 
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Although ebony can be slightly oily/resinous, I would guess that the problem is more associated with the high density. Strong bonds with wood usually rely on the adhesive penetrating into the grain of the wood and then once the solvent has has evaporated leaves a bond that in many cases can be stronger than the wood itself. So, there are two factors that have an impact on strength, one is oil (which repels most water soluble glues like Titebond, etc.) and density which prevents the glue and solvent from sinking down into the wood grain.

Denatured Alcohol may work somewhat (and it is what I use); however both are polar and technically should not do not do as good of a job removing oils as do non-polar solvents like Turpentine and Mineral Spirits. This is because oils are usually nonpolar compounds so they dissolve more readily in other nonpolar compounds. (This seems counterintuitive to me because I have always thought Mineral Spirits and Turps to be kind of "oily" themselves - that's why I use Denatured Alcohol).

There are some authoritative sources that suggest that wiping with Acetone does improve bond strength in woods with "oily extractives". ("Practical solutions for furniture and structural bonding" as found in Chapter 10 of the Wood Handbook a Forest Products Laboratory publication and General Technical Report from the US Dept. of Ag Forest Service)

It also suggests that sanding can help break up the surface of dense woods to provide more tooth for adhesives to grab onto. Sawing and planing can actually burnish the surface of some woods so they need to be scuffed up much as one would scuff up the brass tubes to improve adhesion.
 
jttheclockman said:
I would forgo the sawdust and use epoxy. Color it to whatever you want. Epoxy will stick to just about anything.
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This is a practical suggestion, but then the final product won't be made of ebony and bloodwood, which is where some of the appeal comes from. In this case, it's not a pen, but a "magic" wand, so the innate beauty of the woods used is not the only consideration. Different woods have different "magical" properties.
In a sense, I'm "seasoning" the ebony with the bloodwood in the same way you'd add salt or pepper to a dish in order to impart additional flavors.
It's a niche market, and the people want what they want.
 
egnald said:
Although ebony can be slightly oily/resinous, I would guess that the problem is more associated with the high density. Strong bonds with wood usually rely on the adhesive penetrating into the grain of the wood and then once the solvent has has evaporated leaves a bond that in many cases can be stronger than the wood itself. So, there are two factors that have an impact on strength, one is oil (which repels most water soluble glues like Titebond, etc.) and density which prevents the glue and solvent from sinking down into the wood grain.

Denatured Alcohol may work somewhat (and it is what I use); however both are polar and technically should not do not do as good of a job removing oils as do non-polar solvents like Turpentine and Mineral Spirits. This is because oils are usually nonpolar compounds so they dissolve more readily in other nonpolar compounds. (This seems counterintuitive to me because I have always thought Mineral Spirits and Turps to be kind of "oily" themselves - that's why I use Denatured Alcohol).

There are some authoritative sources that suggest that wiping with Acetone does improve bond strength in woods with "oily extractives". ("Practical solutions for furniture and structural bonding" as found in Chapter 10 of the Wood Handbook a Forest Products Laboratory publication and General Technical Report from the US Dept. of Ag Forest Service)

It also suggests that sanding can help break up the surface of dense woods to provide more tooth for adhesives to grab onto. Sawing and planing can actually burnish the surface of some woods so they need to be scuffed up much as one would scuff up the brass tubes to improve adhesion.
Click to expand...
Thank you for the through explanation. I'll give mineral spirits a try when I get back out onto the lathe on Thursday. Life has gotten in the way the last week, and I'm getting antsy to get back out and get this project finished.
 
RunnerVince said:
Thank you for the through explanation. I'll give mineral spirits a try when I get back out onto the lathe on Thursday. Life has gotten in the way the last week, and I'm getting antsy to get back out and get this project finished.
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Forget denatured alcohol and mineral spirits. wasting your time. You have 2 very oily woods you are trying to adhere to one another. The saw dust soaks up the CA and you can not put enough on it to work. When making pastes from wood you use wood glues and not CA but again they will not work with that type of project. If you get it to stick, one jarring blow and it would probably crack and fall out. CA dry hard and solid. Just trying to help. Acetone is the best for cleaning oily woods
 
I was able to finish the project, and thought I'd post some pictures. I wish I could get better photos, but glossy blank is a bugger to photograph.

I ended up deepening and undercutting the grooves to create a mechanical bond. I would have used epoxy or white wood glue, but I had neither, so I stuck with the CA glue. In the end, the result is good, and someone will love it. However, I think I could improve by:
  • Using a different adhesive, as suggested
  • Going a little deeper toward the edges (there are a few places the diamond pattern doesn't meet with the two rings)
  • Using finer dust: I used turning shavings that I ran through a spice grinder, but the natural lighter streaks in the bloodwood created some larger, still visible pieces. I should have put a fresh piece of sandpaper on my faceplate and took my cutoff of bloodwood to it to create the dust.
Thanks again everyone for the suggestions,

Vince
 

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Have to say a little surprised you got the CA and saw dust to adhere well. Never hurts to try as they say. Nice job.
 
jttheclockman said:
I would forgo the sawdust and use epoxy. Color it to whatever you want. Epoxy will stick to just about anything.
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No reason you couldn't mix the sawdust into the epoxy as well...it should stick to and mix with the dust as well as bond to the base wood.
 
jrista said:
No reason you couldn't mix the sawdust into the epoxy as well...it should stick to and mix with the dust as well as bond to the base wood.
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That is the reason I said it CA has a tendency to clump and absorbs so fast into dry saw dust. I say it will mix even better. Heck they make epoxy wood putty colored already.
 
jrista said:
No reason you couldn't mix the sawdust into the epoxy as well...it should stick to and mix with the dust as well as bond to the base wood.
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As I said, I just didn't happen to have any epoxy on hand, or I would have gone for that. Even a five-minute epoxy would have given a better working time, and a better overall experience. That alone would have been worth it, even if the finished product came out about the same.
 
It looks like the two woods dust combined to make it look murky. I had similar experiences. My solution was to pre finish the darker wood before doing the inlays. They turned out better in contrast.
 
MDEdwards said:
It looks like the two woods dust combined to make it look murky. I had similar experiences. My solution was to pre finish the darker wood before doing the inlays. They turned out better in contrast.
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It actually looked that way prior to finish, and because the inlay was soaked in CA, I'm pretty sure there wasn't any color bleeding.

The "sawdust" I used was actually ground turning shavings (I used a spice grinder), so the color didn't homogonize the way it usually does with sawdust. If I were to repeat, I'd take an offcut and actually sand it on the sanding disk I have for the lathe with a paper towel underneath to catch the finer dust. I think that would have given better color on the inlay.
 
I see what you are saying. Something else occurred to me was some woods darken dramatically with CA glue is mixed in. I have jars of sanding dust and have mixed in maple to lighten the mix. One such is teak, it goes really dark. That might not work, if your customer has a problem with doing that. Just my two cents.
 
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