Advice: Wood Glue Ups
One man's opinions
This video clip has some good general tips to start with.
Don’t over-clamp the joint. I’m right-handed, so I use the left-hand cue i.e. the turn the clamp with my left hand just enough. That gives me a good feel for the tightening. There is a lot of gluing in an end grain cutting board. So, make the clean up easy by applying just the right amount of glue (as above). If there is squeeze out, resist the temptation to clean it right away. Just wait 10-20 mins until the glue gets a bit tacky and starts to bead. You can then just scrape the excess away without it smearing on to the adjoining surfaces. This is important - if you are doing a complex glue up, remember: glue changes everything! So, rehearse all the steps a couple of times beforehand. There is a moment of panic that everyone experiences when things go wrong in the middle of a glue-up. Keep all the clamps in the right places, so you can reach everything quickly. Work quickly, but purposefully.
Use cauls to line up the pieces. Cover the cauls with packing tape, so they do not stick to the surface. I did one glue-up in this instance at MN and did not have cauls. I applied a clamp directly on the joint to keep the pieces aligned, but the result was not as precise as I expected. Cauls are better.
Watch this clip for a “next level” understanding of parallel clamps. This could be particularly relevant if you’re gluing wider boards.
It is inevitable that some glue lines will be visible even if you take all precautions. So, you could consider matching the color of the glue with the wood to hide that. In a project with dark wood I used regular Titebond 3. It is white and therefore contrasts with the dark wood. However, it is also food safe, while I believe Titebond’s darker version is not. So, take all factors into consideration. I personally do not have experience with any other glue types outside the Titebond family and end up using Titebond 3 for 95%+ of all the stuff I do.
For me working time of the glue and how long it takes to apply glue and clamp pieces is important.
Putting glue on one or two surfaces is a choice. I try to plan my glue up and break it down to glue a small amount and clamp it carefully within a few minutes. By gluing more I will have to rush and be sloppy to clamp within the same few minutes.
In most situations I would recommend a thin layer of glue on both pieces to increase likelihood of full coverage. Sometimes it is impractical to identify the contact area so it is easier to spread on one side and have it transfer to the other side but then it is easier to have too much or too little glue.
In the case of a cutting board I’d glue one side to save time so I may glue more during the glue’s working time. Titebond 3 has about double the working time of Titebond 1 & 2. Fresh Titebond 3 in the bottle is a very light creamy color, but when it dries it becomes a dark brown. Therefore, the glue lines blend with the dark wood, but would stand out if this was a maple cutting board. Titebond 3 is also waterproof. Titebond 2 (the blue label) is what I use on most project. It is water resistant and dries to a yellow or orange tone. The red label Titebond 1 is susceptible to water and has the shortest working time of the three.
For cutting boards, and almost nothing else, I also like polyurethane glue. This seeks out water; the glue expands into a foam and creates very strong bonds. It may seem extremely messy, but since the outside of the cutting board will be sanded the messy foam is easily dealt with. Polyurethane glue can be from different brands including Titebond, but is what original Gorilla glue is. My understanding is that once dried it is inert and food safe.
Because of the messy expanding foam nature I don’t like using polyurethane glue for much other than cutting boards. Polyurethane glue foam sands off easily and doesn’t gum up sandpaper. With Polyurethane glue and cutting boards I literally run all of my pieces of wood under the faucet to get them wet. I wear nitrile gloves to keep my hands clean and draw a bead of glue on a piece of wood. I don’t bother to spread or distribute the glue. If the bead of glue was an adequate size and moderately near the edges the foam will spread to the entire glue surface. Therefore, I can apply glue quickly and do more in one glue up in a few minutes. Importantly I quickly position my pieces and clamp them securely and double check my positioning. Once dry I would hack away the foam from one side and run the other side through the drum sander. Without good clamping the foaming will push pieces apart and misalign them.
Use just enough glue
You don’t need that much glue. I often see people in a glue-up where there is so much glue squeezing out. That is quite unnecessary. As a visual cue - if you scribble some pencil marks on the surface being glued, they should be visible through the glue that you apply. I personally only apply glue to one surface, though you could just wet the other surface if you think that will give you some margin for error.
Be sure to use enough glue
While too much squeeze out can be an issue with a cutting board, for structural pieces I would encourage too much glue as opposed to too little. I’ve seen a lot of joint failures due to starving the joint and not applying enough glue. Squeeze out is easy to clean up at the time of clamping using a damp paper towel.
Cleaning up squeeze out
I have two tactics I often use to keep things looking clean.
- One, after applying thin film of glue I wipe the edge with a dry finger leaving about an 1/8” next to the edge dry. Hopefully, this is covered by the squeezed glue which also hopefully doesn’t fully re-reach the edge and squeeze out.
- Two, my best trick which I do on most projects that I really care about is to mask the surface. For this I assemble my parts dry and apply blue painters about 1/32” away from the joint on all sides. When I glue I then wipe the glue off the tape before it slops onto any other surfaces. The tape is most easily removed when the glue has dried to its gummy plastic state but can be removed anytime later too. This yields about 1/16” glue affected area along each joint. I don’t consider this perfect, but good enough and easy.