This article was inspired by a question from Dick. He writes:
I noticed on your cutting board tutorial, you put glue only on one side of the joint. I’ve always glued both sides, whether it’s a cutting board or table top. Is that overkill?
In my opinion, gluing both sides of a joint is absolutely not overkill. In fact, I consider it a “best practice” and I nearly always apply glue to both sides, whether it’s a panel glue-up or a mortise and tenon joint. In the case of the cutting board, I only glued one side because it made things much faster. Since I knew it would take a lot of time to get my cauls in the perfect position, I needed to save time wherever I could. Had I not taken this precaution, I would have been sweating bullets and racing the clock. The fact that I have dry Arizona air really speed ups the dry time of woodworking glue. So that’s really the only time I put glue on only one side of a joint: when I need to save time.
If you’re ever going to try this, there are a couple things to keep in mind. First is the amount of glue. Normally I put a light coating on both pieces, so it only makes sense that when coating only one surface, we should use a little more glue. When the two surfaces make contact, the glue will spread to the second surface and any excess will squeeze out. You can improve the effectiveness of the glue transfer by rubbing the joint. By rubbing the two pieces back and forth, not only will the glue distribute nicely, you’ll also pull the pieces together via a phenomenon known as cohesion. With good even clamping pressure, the joint should suffer no ill effects of initially having glue on only one surface.
To sum up, I recommend putting glue on both sides of every joint. But if you’re pressed for time and dealing with a tricky glueup, you just might want to consider putting glue on only one side and following the steps outlined above.