How can I avoid staining when gluing up?
I use a lot of redwood, and sometimes the glue squeeze-out leaves a blue stain on my projects. I typically wipe off excess glue with a damp cloth or sponge, so what's causing this staining?
—John Tjoelker, Quincy, Washington
It may be contaminants in the glue or minerals in the wood, John. Blue streaks in redwood can even be caused by dyes or contaminants in the cloth or water you use to wipe away squeeze-out.
Instead of removing excess glue with a damp cloth, allow the squeeze-out to dry until it forms a firm skin. Then scrape it away with a flat-bladed putty knife, as shown above. This way, you eliminate a possible staining source and avoid spreading glue on the wood beside the joint.