Hairline Cracks in Ebony

[Mark R Webster]

Hi guys I am making a small decorative box in which I am using some Gabon ebony. As I was cutting out the parts, I notice some hairline cracks. The cracks are not at this point all the way through the pieces. Due to the cost and limited supply of the material, I hate to toss it, but I also don’t want to incorporate the parts into the box if they are likely to fail later. Have any of you used thin superglue or forced in some epoxy to stabilize hairline cracks/splits with positive results? Any other solutions, other than fully breaking the pieces and re-gluing?
Thanks

[Matthew Hutchinson477]

I actually have dealt with a similar issue using ebony. I was making an ebony tip for a rifle stock so I had to make a butt joint--end grain to end grain. Getting the two pieces to mate perfectly is very difficult so as an insurance policy I looked into ways to make the epoxy as invisible as possible. What ended up working best was dying the epoxy black with Mixol. It's expensive stuff but after experimenting with a few other options I am confident that it is the best, "blackest" dye out there.

If the cracks are super thin then you might be better off with CA glue, and dying the adhesive may not be necessary. But, as an insurance policy it may not hurt.

I would definitely NOT break the pieces all the way and reglue. Every time I've done that it hasn't come out looking as good. Little chips get lost and there are always gaps or pieces missing, and I would think that this issue would be particularly bad with chippier woods like ebony.

[Mark R Webster]

Thanks Matthew!

[Jim Koepke]

In some cases small cracks are caused by the wood being too dry. Applying a little oil, like tung or linseed oil may close up the checks.

jtk

[Mark R Webster]

That is a thought thanks Jim

[Ron Brese]

This is an ongoing problem with Gabon Ebony. In the winter when the shop environment is dry I can see hair line checks in the end grain of stock I have on the shelf. In the spring and summer those checks go away. If you get the material hot the heat can wick the moisture out of the material causing it to check, also if you look at it wrong it can check. Yes, that's an exaggeration but you get my drift. When making plane totes from Gabon there is always some small checks that have to be filled with ca adhesive. Applying ca and sanding in dust is very effective but checks and Gabon Ebony are just inevitable. Collectors of plow planes have told me that they've never seen an older ebony plow plane that did not have a check some where.

Ron

[Mark R Webster]

Thanks Ron very enlightening

[Todd Stock]

Fine cracks are best filled with thin CA. For wider/deeper fills use ebony dust and super thin CA in layers, or ebony dust-filled epoxy. Oils change the appearance of the wood, but do not close cracks due to low relative humidity - that requires hydration (bring the RH to 50% and wait), then repair of the tight crack with CA, which is likely now invisible (mark the crack location to one side with pencil...repair with super thin when hydrated. Oils and wax further complicate an eventual repair - just hydrate, repair, and repeat if you allow your shop to deep cycle on humidity...which is why luthiers shoot for a constant RH in the 40%-50% range.

[Mark R Webster]

Interesting, so when the ebony is dryer again, the CA will hold the crack together?

[Todd Stock]

Interesting, so when the ebony is dryer again, the CA will hold the crack together?

Possibly...and if so, the ebony will likely crack elsewhere the RH cycles. The other option is to fill the cracks as mentioned when RH is low and accept the additional stress that higher RH will generate as things swell...no good answer. I just had a very dried out instrument in with cracks in ebony fretboard, ebony bridge, and the center seam on the top open...two days of pumping as much water into the guitar as it would take (could not get the RH in the chamber above 50%...without a guitar in it, goes to 75% immediately), then another three to stabilize at 45%....repairs and instruction to owner to go forth and sin no more (and properly humidify).

Ebony is difficult to season and really needs to sit for 20-30 years before use...I look for old stock that shows little or no checking, then cross my fingers and mill it up. In small pieces like binding or banding, even poorly seasoned stuff seems to do OK, but larger stuff like knobs, etc. wants well seasoned stock. For projects that will not be babied such as tool components, either old, very stable ebony or a tech substitute (dye and acrylic-stabilized wood, etc) can be used. The gabon is def less stable than the macassar I've been getting, so if that old black ebony appearance is desired, always an option to dye with Fiebing's leather dye...let dry and wax...the dye penetrates, but most components that receive wear may need a touch-up in a decade or so.

[Mark R Webster]

Thanks Todd for your very informative post!!

[Terry Beadle]

I've a ebony smoother and it developed a tiny crack near the wedge edge area on the right side.
The maker recommended using CA glue and light clamping force for an over night fix.
It's been 4 ~5 years later and the fix is working fine.

Enjoy the shavings!

[Mark R Webster]

That's encouraging!!