Q. I know that you can buy special glues that offer extended working time, but I can’t buy this type of glue locally. I’ve heard that you can water down standard PVA (polyvinyl acetate) glue to extend working time, but I’m afraid of weakening the bond strength. If I don’t have the special extended working time glue on hand, what are my options?
—Sam Paley, via email
A. Water-based glue dries in two ways: (1) evaporation of water into the air, and (2) wicking of water into the wood. PVA glues can be diluted with 5% water before beginning to appreciably weaken. The working time increases, but viscosity decreases, rendering the glue more runny and messy. Another way to increase working time is to moisten the joint, which slows the wicking process. With this approach, you’ll need to increase the clamping time to allow the watered-down glue to reach maximum strength. I’d recommend keeping clamps on overnight just to be sure. Of course, your best option is to keep glue on hand that’s designed to provide extended working time—like Titebond Extend or (for exterior use) Titebond II Extend.
—Answered by Bob Behnke, adhesives expert at Franklin International (manufacturer of Titebond glue)
