Wood Lamination Glue-Up Strategies
For several reasons, laminations are almost a completely different type of glue-up when you compare them with all of the other joinery glue-up scenarios. First, the total surface coverage is significantly greater than a mortise and tenon, panel glue-up and even a case of dovetails. Covering a larger area with glue takes more time to apply evenly. With this additional time, you begin to eat into your open working time – or the time you have before things start to dry. Second, the greater volume of glue coverage tends to slip and slide around during clamp-up, making proper alignment tricky. Anyone who has glued up a large butcher block cutting board, or a panel made from several boards can attest to the shifting that takes place. It takes time to get things aligned, particularly on a bent lamination or something like a large workbench top, such as the Split-Top Roubo workbench project I’ve been working on.
There are lots of ways to deal with a lamination glue-up to make them manageable. You can use a roller, brush or large flat scrap of wood to quickly spread the glue over the entire surface. You can also use adhesives with a longer open time like a polyurethane glue, or even a two-part epoxy where you can get up to an hour of open time. These adhesives are also great for outdoor applications, where laminated support beams or bent structures for gardens and patios can will be exposed to moisture and humidity.
Wood biscuits make the shifting easy to deal with, and ensure a properly alignment from one piece to the next but can add an extra step along the way. You can also reduce the total number of pieces you glue-up at one time, assembling the lamination in stages. This allows you to use a standard type II PVA wood glue with a shorter open time of 5-10 minutes. While this may be more difficult with a bent lamination, you can get away with in on a straight-forward lamination like the one on the Split-Top Roubo bench top. The larger piece I needed to glue up was comprised of 9 individual pieces that were 4″ wide and over 6′ long. That’s a lot of surface area to contend with. To make this easier, I glued up three pieces at a time just as Jameel from Benchcrafted suggests. This may have lengthened the total assembly time by a factor of 3, but it made for easy alignment, and a much lower stress glue-up. Once the three segments were together, I assembled them into the one massive 100+ lb. slab.
In case anyone is curious, you’ll need (2) 18 oz. bottles of Gorilla Wood glue to complete the entire Split-Top Roubo workbench project, not to mention a boatload of clamps. Gorilla Glue has been kind enough to sponsor me and provide me with the glue I needed for this project, among others.
I’m also in the process of another glue-up test project that further explores the woodworking phenomenon known as “Glue-Creep“, or glue line telegraphing. We’ll be looking at 7 common glue types, wood grain orientation and the effects of temperature and humidity. I’ll have plenty to talk about, based on some of our initial findings during WIA this fall, so be sure to stop by for an incredibly intriguing, in-depth discussion on glue creep. 🙂