Glue and gluing is an essential component of woodworking. It’s not exactly something that requires a lot of skill or technique, but I have a few tips that should get you started. Here’s what you need to know about glue: the basics.
A trip to the adhesives aisle of your local hardware store of home center can be overwhelming. There are hundreds of different types of glues, seemingly for every situation you might encounter. Mostly, they tout their strength and holding power, which isn’t the only criterion to look for. (Rarely will you need glue to hold a 4-ton weight!)
Today, I am only going to discuss the three adhesives I most commonly use on Woodworking for Mere Mortals. And really, the glue I use 90% of the time is yellow wood glue. Particularly Titebond II.
My go-to glue products:
I use so much Titebond II, that I buy it by the gallon. I even mark the date of purchase so I can see how long it lasts! Usually a bottle lasts me a year to a year and a half. This one is almost empty. It’s important to mention that wood glue does have a shelf life. Check the bottle for an expiration date.
I use Titebond II exclusively. I believe it is the best and only wood glue you will ever need. It has never failed me, providing outstanding holding power. It dries quickly, but slow enough that I have time to adjust and position my work pieces.
I do not recommend Titebond III, however. I used it on my patio table and it left horrible stains on the wood all along the glued joints. Since both glues are waterproof, I see no advantage to version III.
I transfer it to a smaller container for ease of use. This bottle is called a Glu-Bot. It makes squeezing out glue a little easier because it forces the glue out the tip at any angle: you don’t have to shake the bottle and hold it upside down. However, the tip does get clogged and I need to dig out the dried glue from time to time.
This wears out the tip which needs to be replaced. Plus, the seal inside the filler lid wears out and needs to be replaced. Without that seal, the bottle loses air pressure and won’t work properly. So it’s not a perfect system. Using an empty mustard bottle or even picking up a squeeze bottle at the dollar store might be just as convenient.
Applying glue to to the faces or edges of boards is pretty straightforward. I’ll discuss end grain gluing later in this article.
One of the most common questions is, “Should I apply glue to both pieces that I am joining together?” No. I believe this is completely unnecessary and just a messy waste of glue. Most of it will just squeeze out of the joint.
The only thing to be careful about is to make sure you spread glue evenly on the entire surface of the board. Don’t just apply a squiggle or a few dots like you did with white glue in kindergarten!
You can spread the glue with a brush, an old credit card, a playing card, a foam brush or anything else. I often use a silicone basting brush. You can pick these up in the kitchen supply aisle of the dollar store. The bristles are usually too long, so I just cut them in half with scissors. The benefit to a silicone brush is that you don’t need to clean it after gluing. Just let the glue dry and it will peel right off. In fact, it’s kind of satisfying to remove than big hunk of dried glue!
For edge grain glue-ups, I usually spread the glue with my finger. Wood glue is water based, so it easily washes off your skin while it’s still wet.
Slip-sliding and salt?
Often, when you press the two boards together, the glue causes them to slide around making them hard to position. An old trick some people use is sprinkling salt on the glue to prevent slipping. I have never tried this because really this has never been a big enough issue for me to mess with salting. I presume it works, though.
Instead, I just slide the pieces back and forth until they grab, kind of like a suction cup. This also helps to ensure the glue is spread completely on all surfaces. If it still want to slide, I let it set for a couple minutes. That usually does the trick.
For a strong bond, clamping is essential. It’s worth noting however, that clamping is not always necessary or practical. For small, decorative pieces, just set the glued parts in place and they will be fine. But for anything that will be subjected to stress or movement, you should clamp.
Try to apply even clamping pressure on all parts of the boards. The more clamps you can use, the better. You don’t need to tighten the clamps with herculean power. Just enough so that you see glue squeezing out the joint. But don’t worry: you can’t tighten them too much. Some people believe over-tightening will squeeze out too much glue and starve the joint. I think this is impossible and falls into the Woodworking Myths category!
Removing excess glue
How and when to remove excess glue squeeze-out is a common topic of discussion among woodworkers. (Yeah, seriously.)
Some people believe it is best not to ever wipe the glue, because it can pack it into the grain of the wood, making staining or finishing difficult. I believe this can potentially be an issue with certain open-grained woods, but I have never experienced it. I think the glue is too thick to really impact the edge or face grain on most woods.
However, I think this can be a problem if you try to wipe the glue off using a damp rag or sponge. The watered-down glue on the rag tends to spread around the rag and then on to the wood. And since it’s thin, it’s hard to detect until you apply finish or stain, causing ugly blotches.
Some people wait until the glue is half-dry…sort of gummy…and then scrape it off with a putty knife or other scraper. I find that this is difficult usually because the clamps I use are blocking easy access to a scraper. Plus, it requires returning to the project a second time before it’s dry to complete this procedure. I prefer to glue and clamp all in once session, only returning to remove the clamps.
My method is to simply wipe off as much as I can with a dry cloth or my finger immediately. Then once it’s dry and I remove the clamps, I sand off any remaining dried glue. This works perfectly into my workflow, because I always sand joints anyway, regardless of glue, just to make use they are even and smooth.
“Clamping” with nails
One of my favorite techniques when building cabinets and other casework, is to use glue and brads. This is a great way to build things without having to stop and wait for glue to dry.
I apply glue as normal and then sack the pieces together with my brad or pin nailer. The nails alone aren’t strong enough to hold the wood together but they act as clamps, holding the joint together while the glue dries. I can proceed immediately to the next step in my project.
Of course, there is one big drawback: the nail holes will be visible. This is not a problem in cabinets where these joints won’t show. Or, if the project is going to be painted you can easily fill the holes with Spackle or wood putty and they will never show beneath a coat of paint.
If these areas will be visible and you are making something really nice, something you want to stain or finish, just take the time to use clamps instead. Filling holes and getting them to match the surrounding wood is a highly skilled technique that most of use are unable to master. Whenever I try, it looks horrible!
Gluing on the end-grain of a board is never as strong as face or edge-grain gluing. The end of boards are highly porous. These are the hollow routes water and nutrients use to travel up the trunk of the tree. When you apply glue, it soaks into these pores like a sponge.
That said, “Never Glue End-Grain” is another woodworking rule meant to be broken. There are times, when it’s perfectly acceptable, gluing together picture frames for instance. A frame spends it’s entire life hanging on a wall, untouched and won’t be subjected to any movement, stress, or abuse.
If you are building something that will be subjected to forces, say a table or chair, then don’t rely on end-grain glue alone. Add some mechanical fasteners such as screws.
Improve the strength of end-grain glue-ups
To improve the end-grain bond, make a glue sizing, sort of a pre-conditioner, by mixing wood glue half and half with water. Apply it to the end grain. You will see it soak in instantly. Apply it liberally, filling as much of the pores as possible.
Let it dry for a few minutes, then apply full-strength glue as normal and clamp the pieces together.
Another method, the one I usually use, is just to pack full-strength wood glue into the end grain, forcing it into the pores. You can actually feel the glue pushing into the grain with your thumb. After a bit of packing, glue up your pieces normally.
Gluing wood to other stuff
Wood glue works great at one thing: gluing wood to wood. But sometimes you need to join wood to other materials such as metal, plastic, glass, etc. My go-to adhesive in these cases is epoxy.
Epoxy comes in two parts. I usually get the 5-minute epoxy that comes in a two piece bottle that squeezes equal amounts of each component.
Mix them together and apply small dollops. It’s a lot messier than wood glue, but epoxy doesn’t require any clamping. It’s probably not as strong as wood glue when joining wood to wood, so I wouldn’t use it as a wood glue replacement.
However, if there were “one glue to replace them all,” it might just be Weldbond. I’ve only recently been testing it and find myself using it more and more. It seems to bond just about anything and does it well. I’ve used it for glass, ceramics, terra-cotta, painted wood, plastic, and more. Plus…and this is a cool thing: You can let it dry on two pieces and use it as contact cement. And it dries clear.
I haven’t had a chance to do any side-by-side testing, but I would love to see how it stacks up against Titebond II.
Whatever you use for gluing things, remember that a glue’s strength and holding power is only one component. Glue marketing wants you to believe that this should be your only criteria when making a purchasing decision. There are many other factors to consider, such as ease of use, clean up, volatility, environmental impact, long-term holding, weather resistance, etc.