What Wood Glue to Use?
Wood glue can be confusing to understand because there are so many options out there. I'll break it down for you, so you know which bottle to grab for your next project.
For woodworking, these are the wood glue options you have:
- PVA Glue (aka Yellow Glue or Carpenter's Glue)
- Hide Glue
- Fish Glue
- Polyurethane Glue
- CA Glue
- Contact Cement
For the majority of woodworking projects, PVA glue is the glue you want to use. This works by soaking into the wood fibres and bonding them together in a way that is normally stronger than the wood itself. There are some things you need to understand though about the limitations of gluing wood together. It has virtually no strength if you glue end grain to end grain. It works very well edge grain to edge grain (think of gluing boards together for a table top). It works well for furniture joints as well where the grain of one piece is perpendicular to the other.
Glue can lose it's effectiveness over time so I recommend writing an expiry date on the bottom of your glue bottle, 1 year from when you open it. It's also important that you don't let it freeze because if it does, it won't work anymore. There's nothing worse than working on a project and having the glue fail a few years later, so take the precaution to store your glue with care.
Yes, this is an old fashioned glue. It's what you will find in antique furniture, but it still has its uses today. It has the unique ability to be heated up to unglue something. If you're repairing loose joints in antique furniture, you should be using hide glue to reassemble the piece. That way, if a part breaks, the joints can be taken apart to allow for the repair. It can be purchased in crystals that can be cooked up into a batch of glue and it can also be purchased in a liquid form. There are two brands of liquid hide glue that I'm aware of; Old Brown and Titebond Hide Glue.
I use Titebond Hide Glue in my workshop and I find in the winter, when my shop is cooler (heated to 10 degrees Celsius or 50 degrees Fahrenheit), it helps to warm up the glue as it gets really thick when cold. I keep it in the house for a while if I'm proactive. If I forget and need to use it quickly, I'll fill a container with hot water and soak the bottle for a few minutes. Another trick I use is to put the bottle in the back pocket of my jeans and let my body heat do the work... it takes longer BUT it works.
Similar to hide glue, fish glue is classified as a protein glue and it's also reversible. What's unique about fish glue is the long "open time". This is how long you have from when you apply the glue to the point where the glue starts to bond. If you've ever done a woodworking project that has many parts, the glue up can be stressful to ensure you get everything together quickly. Typically PVA glue and hide glue give you about 20 minutes for assembly. Fish glue can give you 60 to 90 minutes to assemble your piece.
This type of glue isn't available in hardware stores or home improvement stores. I purchase fish glue from Lee Valley Tools.
If you have a joint with a gap, epoxy is the only glue that has strength to hold together that gap. No other glue will, not even polyurethane when it foams up. If you've never worked with epoxy, it's a 2-part system. You mix a resin with a hardener right before you're ready to glue parts together. There are a variety of products out there, and for small jobs I use JB Weld, which comes in a double barrelled syringe. The consistency is thick, like molasses. When you squeeze the syringe, the right amount of resin and hardener are dispensed for you to mix up.
For larger batches or thinner glue, I use the West System epoxy. This is a 2 part system that has pump dispensers. You put one pump of resin in and one pump of hardener for a perfect ratio of the components to mix up. This is thin enough you can put it into a syringe with a blunt needle tip and squeeze it into tight spots. It's also good for pouring into cracks that can't be clamped closed and glued up with other glues.
Regardless of what you see in advertising, polyurethane glue is not the end all be all of glues. Its unique super power is that it is waterproof. For woodworking projects, that means if you're building something for the outdoors, this is the glue you want to use. Don't be mislead by PVA glue labelled as "weather resistant" because it doesn't hold up over time... I know from personal experience on my own projects.
There's a unique way this glue is applied. One side of the joint needs to be moistened, which activates the glue and the other side is where you spread the glue. After you clamp the parts together, you'll likely notice some foam building. That's normal, but don't confuse it with a gap-filling glue. The foam has no strength, so you can't rely on it to fill the gap and hold it together. If you need a gap filler, you can purchase polyurethane glue in a tube you use with a caulking gun. This type of polyurethane glue is typically used in construction and makes a big mess if you're not careful with it.
Clean up for this glue is not easy, so I recommend wearing protective gloves and having some rags on hand to clean up any drips.
If you have to do work quickly and don't have time for glue to dry, this might be a glue for you. CA glue is sometimes used for trim work, especially where small parts are involved. You can use it straight out of the bottle or you can use it with a spray on activator, which instantly bonds the pieces together.
There are different consistencies and colours available in CA glue. Thicker glue is good for filling voids and is popular for wood turning and live edge work where bark or inclusions need to be stabilized.
I rarely use this in my workshop, but when I'm repairing a piece that has laminates on it, this is the best glue for the job. It's a very unforgiving glue to use because you can't reposition your parts once they touch together. It requires a lot of pressure from a roller to ensure the two parts meet effectively too. If you have a need to use contact cement, consider the water-based formula, which is less toxic than the traditional formula. This is the most potent smelling glue and needs to be used in a well ventilated area.
Best Glue for the Job?
Here's a brief cheat sheet for when to use what glue:
- Outdoor Use - Polyurethane Glue
- Antique Repair - Hide Glue
- Gap Filling - Epoxy
- Quick Setting - CA Glue
- Slow Setting - Fish Glue
- Laminates - Contact Cement
- Everything Else - PVA Glue