Gluing up a wood panel is one of those things that seems deceptively simple, until you try it and end up with a cupped mess of a panel covered in goopy lines. Here are some best practices to help you glue up a beautiful, flat panel on the first try.
Step 1: Applying the Glue
For applying glue to small sections, like the edges of boards or intricate finger joints, a small, flat brush is ideal. Flux brushes, found in the plumbing section of the hardware store, are great for this. If you’re covering a large section, a cheap notched plastic trowel works well for spreading glue evenly.
When gluing together many boards to make a panel, it’s tempting to glue and clamp them all at once, but that can lead to cupping problems and have you racing the clock trying to get all the pieces glued and clamped before the glue starts to dry. Saving a little time in the short-term isn’t worth serious long-term problems. To make sure your surface stays flush, add just one board at a time, then wait half an hour for the glue to set before adding the next.
Sometimes it’s easier to finish project pieces before assembly, but if finish gets onto the joints you’re planning to glue, the glue won’t adhere as well. To prevent this, use masking or painter’s tape to cover the places where glue will go, then remove the tape to reveal bare wood before gluing.
Before popping the top of that glue bottle, always dry fit your pieces to make sure the joints fit well. Fit problems are a lot easier to fix before adding glue. Dry fitting also gives you a chance to figure out how many clamps you’ll need and where to place them before you start, so you won’t waste any time once you have glue drying on your boards.
Try to use similar clamps to apply force evenly and prevent warping. To avoid marring the surface of your project, use wood scraps between the clamp and the surface. Cover these scraps with packing tape to keep them from sticking if they come in contact with glue. Make sure to clamp over glue lines to keep boards flush.
Use cauls to keep your boards aligned on top and bottom, then attach clamps to the cauls; a few 2x4s may be the most cost-efficient tools you can buy to keep the boards in a glue-up panel flat. Alternate your bar clamps over and under your panel to prevent cupping.
Beware of over-tightening clamps, which can lead to cupping and too much glue squeeze-out. Instead of fully tightening each clamp to begin, tighten each part way, then go back and tighten each a bit more in turn. Once your assembly is glued and clamped, leave it in place for an hour before moving it.
Step 3: Removing Glue Squeeze-Out
There is a great debate over when the easiest time is to remove glue. Wipe it off while it’s still wet and you can cause some of it to absorb into the surface of your project. Wait until it’s dry and scraping it off can be difficult and damage the surface. We think the best time to remove glue is half an hour to an hour after application, once it’s started to gel, but hasn’t hardened. At that point, you can scrape it off with a chisel without too much trouble.
Looking for an even easier solution? Apply painter’s tape to the edges where you expect squeeze-out before gluing boards together, then, when the glue is still wet, just peel off the tape.