Many of our woodworking projects require gluing up multiple planks into a wider panel. The most common clamp that is used for this is the pipe clamp due to its wide availability and low cost.
Pipe clamps do many things well: they apply even pressure, they’re easy to use, and they extend easily to longer lengths using pipe couplers. One downside to using pipe clamps for this, however, is that they can introduce black stains into your panel. Those stains can run pretty deeply into the wood. If the stain happens to be on the show face of your panel, you might find that you have to plane off a lot of wood to eliminate black pipe stains. If you would prefer to eliminate black pipe stains before they happen, there are several approaches that can be effective.
Apply wax. By waxing the pipe occasionally, you will accomplish a couple things. First, it can be effective in eliminating black pipe stains. Second, if you have problems with glue squeeze-out getting onto your pipe clamps, it can also make it more difficult for glue to stick to the pipe, which in turn makes it easier to clean your pipe after a glue-up.
Tape it. By applying a layer of painters’ masking tape to the pipe before starting the glue-up, you can prevent the black stain from migrating into the wood panel.
Plumbing couplings. Slip a few PVC couplings over the pipe to create a gap between the pipe and the wood panel, thereby eliminating black pipe stains.
Galvanized pipes. Rather than using black pipe, use galvanized. These can work equally well for clamping, plus have the added benefit of helping you eliminate black pipe stains. Be aware of the downside that George discusses in the video.
The next time you have a project that requires a panel glue-up, try one or more of these tips and let us know how it works for you.