Are Glue Smears Really a Problem for Finishing?
I watch as many woodworking programs on PBS as I have time for. None of them pays any attention to glue smears on raw wood, except for maybe a "wipe off the excess glue" statement. It seems to me that the glue is already in the wood pores, and that will affect how the raw wood takes a stain. If that's not the case, what am I missing? - Jim Sommerfeldt
Chris Marshall: Jim, leaving glue residue on raw wood absolutely will affect its ability to absorb stain, and typically the stain won't soak in at all over the glue smear. Result? An ugly spot on your project — like the ones showing up here and there around the dovetails in the photo at left). I try to avoid them by taking several preemptive measures. First, I limit how much glue I use so I don't get drips and smears in the first place. I don't spread glue with my fingers, because that just increases the odds that my sticky fingers will leave "tracks" behind that I might miss later. I keep a sponge and pail of clean water on the bench whenever I'm carrying out a glue-up, but I scrub only after I've removed as much congealed glue as I can with a putty knife. (Some woodworkers avoid the sponge altogether because it can still leave glue residue in the wood pores; I haven't experienced that problem myself.) Then, most importantly, you've got to sand your project thoroughly to remove any final traces of glue. Start with the coarsest grit that will be required to remove machine marks, and work up to 180- or 220-grit. Scraping, scrubbing and sanding is my regime. I've even given project surfaces a wipe down with mineral spirits or denatured alcohol after sanding to check for traces of glue, especially when I'm planning to used aniline dye or pigmented stain. It makes any last bit of glue residue easy to see and doesn't raise the wood grain.
Tim Inman: Good eye! Actually, the PVC and PVA "yellow glue" type products are much worse about showing glue spots than most other types. The soft old original white PVC Elmer's® glue is still the king of the heap when it comes to leaving glue smears in finishing. Clean glue joints are always the goal. However, the harder the glue, the easier it is to sand it out and stain over it. One really magnificent quality of plain old brown hide glue is that it takes stains pretty well, and it cleans off easily during glue-up with just a damp cloth.