Gluing Ipe
Wood sold as "Ipe" may represent a variety of tree species. Some specimens at least are reported to be difficult or impossible to successfully glue. August 12, 2007
Question
Our shop has been experiencing delamination with glued-up ipe. We have tried different types of glues and are currently using West Systems 2 part epoxy for this and still have trouble. All glue-ups have been properly clamped. Any ideas?
Forum Responses
(Adhesives Forum)
From Jeff Pitcher, forum technical advisor:
Ipe is very dense and often difficult to glue. Make sure you are using freshly machined pieces and, if necessary, wipe the gluing surfaces with mineral spirits to avoid glue line contamination.
From contributor D:
Others will disagree with me, but I am of the opinion that ipe does not glue. At least over time. I have seen one spectacular failure that put a local shop out of business. This very public use of ipe glued into corbels and laminated squares is now held together with screws and nails and anything they can find. I happened to visit the shop while they were fabricating the parts, and they were then convinced that the $200/qt epoxy was going to work. It didn't.
After hearing such different outcomes, since some people say it is not hard to glue, I'm convinced that ipe is a name for a collection of species, and that some species go to one area of the US, by distribution, and another species goes to another area. They look and work similarly enough to be grouped together, but some characteristics are markedly different. Just my guess.
From Professor Gene Wengert, Sawing and Drying Forum technical advisor:
Ipe has a chemical (lapacho) that will migrate to the surface and create poor gluing even with epoxy. The wood has a very high density, making it tough to glue. The interlocked grain means that any MC change will result in uneven surfaces and poor gluing. But, the wood does glue well if surfaces are freshly prepared (within minutes) and are cleaned with a solvent a few minutes before gluing. Of course, all other standard gluing procedures must be followed, which includes avoiding excessive pressure and having enough glue.
From contributor B:
Contributor D, your suspicions are correct. Ipe comes from "more than a dozen species belonging to the genus Tabebuia." The many species of Tabebuia are "so varied in their texture, density, and appearance that the lumber industry sorts them into somewhat loose categories based on the properties of the wood rather than by the species that produce them." This is from the June 2002 edition of Fine Woodworking.
From contributor D:
So... I'm thinking that ipe should not be glued for width or thickness - probably the safest approach. Therefore, is it ever available as 8/4 or 12/4?
Or maybe it is possible to go to the supplier to find out what the species really is, and then attempt to glue if it is a variant that does glue well. But how does one really know what the true species is, and whether it does glue, doesn't glue, or may glue? While experiments may show that it does glue okay, what about the integrity over time? Especially since ipe's properties tend to place it in some pretty harsh situations. Questions from a hopeless paranoid.
From contributor P:
Forget it, it can't be done. We have tried many times, and many ways. With ipe, it will fail with time, every time. You must use mechanical fasteners. In a pinch, we have used pocket screws and sliding dovetail joints in the past in addition to epoxy adhesives. Adhesives alone will not work.
From contributor A:
I would do a few test samples before getting involved. One thing to consider when using epoxy resins is proper prep. A lot of people are not aware that all surfaces should be sanded coarsely when gluing with epoxy. Whereas white/yellow seems to stick better to freshly jointed wood. Until you do curved epoxy laminations, this is usually not a problem. If not sanded with a 60 grit widebelt, the laminations will delam. Try sanding with 80 grit, clean with acetone, then epoxy.
From contributor M:
I too have had some unpleasant experiences with delaminations with ipe. I have been using poly glue, Titebond, and nothing seems to work every time. I make Adirondack chairs and garden style benches. I do pin the M&T joints on the benches and use ss screws. I try to use all the scraps I can, and glue up 1x's for use as 2x4's. After hearing all this, I will now insert screws to maintain the integrity.
From contributor T:
For 12/4 ipe and the like, go to Ipedepot.com. Can't say it won't cost you an arm and a leg, but it's out there. By the way, I did see an outdoor bar top done with ipe that was held together with all-thread screws and sealed in the joints with silicone (i.e., used just as wood glue in the joints). Was done by the restaurant's contractor that had it left over from the deck. Not "interior grade good looks," but certainly accomplished the goal and looked good outdoors.
