When I was a kid the only glue I remember seeing was a white bottle that had an orange label and the bust of a happy cow on the front. Various sizes of that bottle were everywhere — small ones in the craft room at school, and big beat up ones in my grandfather’s shop.
Modern woodworkers are spoiled for choice when it comes to selecting what kind of glue to use on a project. No matter what the application, there’s an adhesive that will get the job done. It’s all a matter of knowing which one to use in each situation. Here’s a quick look at four of the more useful glues you should have in your shop. Then we’ll take a look at what epoxy can do.
PVA GLUE.
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| For most basic woodworking tasks, PVA glue is the right choice. |
Polyvinyl acetate (PVA) is the go-to glue for most woodworking applications. This familiar yellow adhesive is economical and the first choice for any project that’s going to stay indoors. The great thing about this type of glue is the array of different options for specific uses.
You can now find water-resistant formulas as well as ones that offer long open times (the time you have to assemble the parts before the glue starts to set up). Another big plus is the availability of PVA — it’s in any hardware store or home center.
POLYURETHANE.
The next glue on my list is polyurethane. You’re probably familiar with this glue. It’s notable for its foamy squeezeout at the glue line. Polyurethane is perfect for projects that will be in contact with moisture. It’s waterproof and plenty strong.
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| Polyurethane glue foams as it cures, but provides a waterproof bond. |
There are a couple of things to keep in mind when using polyurethane. First, it bonds best when you dampen one of the parts being joined. The glue needs moisture to set up and cure properly. Second, don’t try to scrape or wipe away the foam when it’s wet. It’s much easier to let it dry and then scrape it off.
HIDE GLUE.
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| Liquid hide glue can be purchased in convenient sizes. It dries hard, but can be reversed with water and heat. |
Another glue I like is liquid hide glue. Of course, hide glue has been around for nearly as long as people have been working with wood. You can make it yourself, but newer, bottled varieties are easy to use.
The advantages of hide glue are many — a long open time, easy cleanup, and a hard, non-elastic finish when cured. Many of us here at Woodsmith find ourselves reaching for hide glue more and more. It’s a good choice for just about any indoor project.
CYANOACRYLATE.
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| A drop of cyanoacrylate will temporarily bond a metal hinge to a wood frame while you scribe the outline with a marking knife. |
Next up is cyanoacrylate, also known as CA or super glue. While very useful, it’s also the most expensive common glue. Like epoxy, it’s great for gluing up dissimilar materials. But its main attraction is its instant bond. A drop of glue on anything (including your fingers) and you have a very fast-setting connection. The photo below shows a handy application.
Cyanoacrylate can be found in thin, medium, and thick viscosities, useful in different situations. You’ll want to consider using an accelerator if you want the quickest bond. And no matter what type you use, make sure to have a bottle of debonder on hand for the inevitable, accidental glueup. I’m speaking from experience here.
EPOXIES
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| There’s a wide variety of epoxy products available. The gamut runs from quick, simple systems to use around the house, all the way up to epoxies that boat builders rely on. |
Epoxies are a step beyond the glues we just looked at. In short, the two parts of epoxy are a resin and a hardener, or curing agent. When the two parts are mixed, a chemical reaction occurs to form an incredibly strong adhesive that is waterproof and doesn’t shrink.
ADJUSTABLE.
One thing I like about epoxy is that its curing time and consistency can be modified to suit the task at hand. For example, when I’m assembling a project with a lot of parts, switching to a hardener with a longer setting time will give me some breathing room to get all the pieces in place.You can also modify the consistency of the epoxy. Changing the thickness comes in handy if you’re working on sloped or vertical surfaces. Here a thicker epoxy won’t drip and run.
DIFFERENT MATERIALS.
But the best thing about epoxy is its ability to glue together different materials, like metal to wood. Working with epoxy can seem a bit intimidating. Unlike wood glue, you have to mix up precise proportions of resin and hardener each time you use it. It’s the mixing stage that can trip you up and result in a poor-quality joint. But with the right techniques, you’ll find yourself using epoxy more often.
USING EPOXY
The first step in preparing epoxy is getting the proportions just right. The typical ratio is one part resin to one part hardener. But the ratio may vary from one manufacturer to the next. So it’s a good idea to read the directions.
Once the two parts are mixed, the curing process can’t be stopped. So try to measure out only enough resin and hardener to do the job.
To make mixing and cleanup as easy as possible, I’ve found wax paper or disposable plastic containers work well. Just steer clear of foam cups. The curing process generates enough heat to melt them (trust me, I know).
MIXING.
Mixing up epoxy isn’t like stirring cream and sugar into your coffee. If an epoxy joint fails, you can trace it back to one thing — mixing. A square-tipped spatula makes it easier to get all the resin and hardener mixed together.
Safety Tip: Any time you’re using epoxy, it’s a good idea to work in a well-ventilated area and wear gloves and eye protection.
MIX & MIX SOME MORE!
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| To maintain the proper ratio, measure out the recommended amounts of the resin and hardener side by side. | Use a square-tipped spatula and combine the two parts in a swirling motion. |
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