How Much Glue?

Article - July 7, 2009

This question comes from Adam who asks:

I have been at this hobby affectionately referred to as woodworking for about a year and a half now, and I’ve made some pretty decent projects. No substantial furniture, but some nice smaller things. I was in the process of making my most recent project, a box to hold pictures and sit on a coffee table, and I had an epiphany. Every project I have done has had the same problem. GLUE!!! I think I have been making the rookie mistake for WAY too long and thought I would see if you had any input on it. I ALWAYS use entirely too much in my joints. I use blue tape and allow it to skin over and scrape it away, but it is still normally a pretty big mess. I’m always scared that I’m not getting enough glue in the joints when I try to use less, so then I worry myself until I put more. So as a request, could you include a couple of close-ups of your next glue up so that I can get an idea of how much is the right amount? I know as of now that I am using too much, I just don’t want to use too little and have my projects fall apart. I’ve heard time and time again that a thin film is plenty on the joints and I realize that squeeze out will occur”¦but not as much as I am experiencing. Also, the word “thin” is relative. What I put on is a “thin” coat”¦until it squeezes out and runs all over my blue tape. Lol thanks for any help you can throw my way.

And here was my reply:

squeezeoutHey Adam. In the Steamer Trunk Pt. 3, I believe I showed a good shot of a rabbet joint being glued up, and you can clearly see the squeeze out. If I recall, that joint was a little wetter than I usually like. But it was a pre-finished piece so the squeeze out was easy enough to clean. Now as a general rule of thumb, as long as each adjoining piece is coated completely, you have enough glue on the joint. You are right in that all you need is a thin film. And from what I understand, the thinner the film, the stronger the joint.

Now let’s talk about how thin the coating needs to be. Think of painting a wall. You don’t slop the paint on real heavy, right? Instead, you roll it out into one smooth continuous thin layer. And that’s what you should do with your glue joints. In general, you want to make sure each part of the joint has glue from edge to edge. And if you want to add a smidge more for good luck, go ahead.

butterbagelOh and here’s another way to think of it. I just love food analogies! Let’s talk bagels: butter vs cream cheese. When it comes to butter, most folks like a nice thin coating of butter from edge to edge. And with cream cheese, people tend to like a more generous helping. Some crazy people actually like so much cream cheese that its more like having a bagel with their cream cheese instead of the other way around. (I am qualified to speak on this topic because I spent a full year working at a My Favorite Muffin in Princeton, NJ). So glue should be spread more like butter, instead of like a schmear of cream cheese. Now I’m hungry! Lunch anyone?