Replies

1. 
   Sgian_Dubh | Dec 08, 1999 04:01pm | #1

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   Like other oily timbers, Wenge can be difficult to glue and polish, but if you can drive back the oiliness, and then fairly quickly do either process, then most standard procedures should be succesful.

   For joining boards to make a table top, I think a properly formed straightforward butt joint might be best in preference to a complicated wriggle or other form of interlocking joint. You might want to add a few biscuits primarily for the purpose of alignment in the thickness. As such, I don't aim to
   b specifically
   glue the biscuits with highly visible table tops, for I have observed that they can telegraph through months and years later as rugby ball shaped ovals. If a little glue dribbles into the slot, that's fine though.

   With a butt joint you have just two flat surfaces to clean of oiliness prior to gluing, and this is simpler and will probably be more successful than trying to clean more complex joints. Acetone, and lacquer thinner will both drive the oiliness back enough to quickly get the glue on and assemble the parts. But to work well, I believe the quicker the glue goes off, then in a sense the better. Regular PVA should work well, and the yellow stuff goes off fastest of all. You may want to glue just one board at a time to build up your width, i.e., clean two edges to be joined, apply the glue, cramp up, all in short order. If you are doing quite a small table top, you will probably be able to do it all in just one go.

   I've had a good success rate with the glues I've used in the past. These include, PVA, hide, epoxy, and urea formaldehyde. I prefer not to use epoxy if I can help it, but only because it is not fond of shocks, it's rather messy, and very abrasive on the cutting tools after.

   If you choose to use epoxy, I have found the System West range to be reliable. Mixing is easy. Equal numbers of shots out of each can, swizzle away to blend, apply, align, cramp up. The larger the quantity mixed though, the quicker it goes off, because it generates heat, and a largish volume will kick it off very quickly and soon be unusable.

   I have no experience of polyurethane glue and oily timber, so can't really advise you. However, here are a couple of points to ponder, and both would make me hesitant to use it.
   *I can break polyurethane bonds quite easily in similar applications on non oily timbers. I've done this with the offcuts from the end of a table top glue up. It's not a strictly scientific test I know, but this always makes me wonder just how strong polyurethane really is.
   *Polyurethane takes several hours to go off, and I wonder if the oiliness in the timber could migrate back to the glue faces prior to the glue curing, and therefore cause a weak bond.

   However, regarding the latter point I said earlier that I've had success with urea formaldehyde, and that also takes several hours to cure, but I suspect with this glue that the moisture in it is holding back the oil until the glue has cured.

   As a matter of interest, Wenge does not polish up nicely with pure oil finishes. It tends to look muddy.