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What's with my ebony?!

I made a turning block by gluing up a 2"x2"x6" block of ebony, with

2"x1"x6" blocks of wenge on either side, and 2"x1"x6" blocks of granadilla on either side of that. On the bottom I glued a 6"x6"x1" piece of walnut. So the whole thing was 6"x6"x3". It was glued up with polyurethane.

It turned out "interesting"; a bit dark. But a week later the ebony on one side seems to have shrunk. It has recessed 1/64" from the wenge, and many have partly broken off from the wenge, though it is not clear. The other side seems fine.

The ebony was wax covered when I bought it, but I never thought it wasn't dry. Should I have let the ebony dry out before gluing it up; or is there another problem. (I mean besides wasting expensive wood on a project like this...)

Reply to
Toller
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Is the grain of both layers going the same way? It should be, otherwise the natural expansion and contraction will tear it apart.

Reply to
Gerald Ross

yes, all the grains are parallel.

Reply to
Toller

Hi Toller,

I suspect that the difference in expansion/contraction rates is behind the separation. I make Ikebana inspired vases by gluing various woods together and then turning them.

Although Bruce Hoadley's table 6.3 "Approximate shrinkage ....." (2000 edition) in "Understanding Wood" does not list wenge or ebony, my experience with ebony suggest that it shrinks significantly less than most other woods. You might try creating some moisture controlled experiments to determine what woods are compatible with ebony.

I have stopped using ebony for the feet of my vases, and only use it for the neck as an accent piece and have found that design is less susceptible to splitting and separation.

Also, I have stopped using Gorilla Glue for these kinds of glue ups because it requires adding moisture to both surfaces before adding the glue. I sand all pieces just before glueup and use Titebond III.

George Saridakis

Reply to
George Saridakis

Couple things. First, ebony, the real dense stuff, is notoriously difficult to stabilize. The importer covered his bets with wax, and though you don't mention how long you seasoned the wood after removing the bulk of the wax, that would be the proper hedge for you to take.

Second, and a bit obtuse here, quarter grain and face grain shrink at different rates, as you know, and sapwood, which is generally lese dense, cycles up and down faster than heartwood. If it's precision you seek in a glueup, glue face to face, quarter to quarter, sap to sap, heart to heart.

Reply to
George

I completely endorse what George said and would also add change your glue. Use either epoxy or the dry powder casein marine type glue. Titebond and all the other "white" or "yellow" glues never really set hard and will lead to creeping of the joints when exposed to humidity changes. Another good choice would be good old fashioned hide glue, (NOT the liquid stuff)

Reply to
Canchippy

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