Professionals and Amateurs Together

Glue for Large Laminated Curves

Question

s any glue better than the rest when laminating large curves, using plywood, when the least amount of springback is desired?— Myrl Phelps

Answer

Richard Oedel replies: This is a difficult question because of so many variables. But I have done a lot of laminating and have a pretty good sense of what works.

First, ignore the standard PVA glues because their glue line is too rubbery. That means Titebond 1, 2 and 3 are off the table. So is Gorilla glue for the same reason.
To keep spring back to a minimum, you need a rigid glue line which means you need time to keep the spring back to a minimum as the glue cures thoroughly.

For big structural type projects, think epoxies. West System and G3 are only two, but there are hundreds of formulations. With West System, which I have used a lot, the glue line is thick, which means you can see it as dark lines between each lamination—ok on some woods, not on others. Ash or maple—no thank you.

But let’s go to one of my favorite products—Unibond. There are two types—Unibond One (great one part glue for veneering, not laminating) and Unibond 800 (a two part glue, perfect for strong furniture laminations). Its light color and thin glue line make it work well for light woods.

With either the epoxy type or the Unibond, the final bond rigidity takes time. If you want almost zero spring back (less than 1/16˝ over 4 ft) you need to wait five days. Be patient.

Then there is the time tested glue—hide glue. It has a hard, thin glue line, easy to apply and reversible. It also needs time for no spring back—same five days. Don’t count the old technology out! It still works just fine.

In all cases, make sure you wet both surfaces with adhesive, and with Unibond, it MUST be over 70° to cure. If you are not sure, buy an electric blanket and drape it over the glue-up for the first 8 hrs. Under 70°, it will fail. Fair warning.

Peter Breu replies: I use Unibond 800 for any laminating. It dries slowly so it needs perfect clamping such as a vacuum bag system. When dry there is no spring back.

Bob Couch replies: Some have had luck with Titebond and I have too if it’s not a strong bend and your laminations are really thin. But I have not had reliable results for lamination glue-ups. I use only Unibond 800 now. It dries to a crystalline structure and there is minimal spring back. You also get a little more working time with Unibond.

Tags: Glue, Laminating