Did you know that a glue-only joint can be stronger or at least the same strength as using dowels or biscuits? This is, of course, if the glue is properly executed. Of course, don’t take this as me saying that no joints benefit from reinforcements. But it doesn’t have to be done.
Certain joints like end grain do need the reinforcing power of dowels and biscuits. This way you have something nice to glue with. However, if you’re joining edges together, you may actually weaken everything if you try using biscuits, dowels, or splines.
It’s important to mount everything correctly. So how does this yellow glue work exactly? The popular thought is that yellow glue is strong because of its chemical makeup. This is when those molecules get into those wood pores and hold everything together in a tight bond that is hard to break. Think of it as being like velcro.
It’s also true that you can’t avoid the glue penetrating some of the wood particles. However, yellow glue gets it strength from something called “specific adhesion.” This is when the wood molecules and the wood bond together.
Simply put, the layer of glue on one end is adhering to the glue on the other piece you’re putting together. This is why you must prepare your edges well. As long as all of the edges are prepared correctly, you can count on the glue becoming even strong than just the wood itself.
Meanwhile, a glued edge joint that’s done properly will not break at the glue line but along the wood itself if it’s broken. When you’re using yellow glue, you must consider three things. The first thing is that the two pieces you’re mating must be as smooth and flat as possible.
The second thing to consider is whether or not your glue is applied evenly. Any interruption in the glue line can mean a weakened bond. This goes for your clamping as well. When you’re clamping on your joint, make sure the pressure is even everywhere along the joint line. Doing so will give you a film that has flowed evenly into your joint and become just the right amount of dense. Remember: beads of glue, not globs! Otherwise you have done it incorrectly and may need to either scrap the project or try to start over again.