Understanding wood glue + 8 awesome tricks you should know

Are you prepared to upgrade your woodworking abilities? As all knowledgeable carpenters know, strong and high-grade wood glue is essential in any craft setting. With numerous choices in the market, it can be perplexing to pick the perfect adhesive for your venture.

Wood glue is one of the most used glues for woodworking and array of options available for wood glue can be overwhelming.

Thus, this article intends to provide comprehensive details regarding all the different types and applications. From indoor vs outdoor use and quick-drying vs slow-drying, you will gain a thorough understanding of this essential tool.

Ready to take your woodworking projects to the top? Our guide has you covered with 8 expert tricks and tips that will elevate your skills.

You won’t have to worry about choosing the wrong adhesive ever again! Become a true guru of glue, and start making masterful pieces of art today.

Disclosure: At zero cost to you, I may get commissions for purchases made through links in this post. I earn from qualifying purchases as an Amazon associate. Products featured are selected based on quality, performance, and reputation, regardless of affiliate relationships.

What is wood glue?

Wood glue is an adhesive that bonds wooden components firmly together. It penetrates the wood surface, forming a more robust bond than the wood itself.

How does wood glue work?

Have you ever considered the science behind the power of wood glue, a popular adhesive choice among woodworkers for connecting pieces of wood?

To gain an insight into the science of wood glue, let’s explore its fundamentals. Applying the adhesive to a surface will allow it to soak into the wood fibers – usually down to two or six cells deep – forming a secure connection. As the glue seeps further in, its moisture starts to dissipate via the wood grain, further enhancing attachment.

Once the glue is absorbed by the wood fibers, and the surfaces are firmly adjoined, the true power of the adhesive becomes evident. This union results in a bond that is exceptionally strong- oftentimes more so than that of the material itself. This is because of the unique attributes of the glue, which allows it to stick tenaciously to the surface while simultaneously keeping its own solid constitution.

The durability of the connection achieved with wood glue is critical for affirming that the pieces being linked remain secured even under great pressure. This is especially paramount in carpentry, where the finished piece must endure long-term use and wear.

The next time you undertake a woodworking project and use wood glue, pause to comprehend the science that goes into this formidable adhesive. Wood glue’s capacity to sink in and create a dependable fastening makes it an exemplary tool for any woodworker’s workshop.

Related article: Is Wood Glue Stronger than Screws? An Unbelievable Showdown!

Wood glue classes

When purchasing wood glue, make sure to look out for the letters D2, D3 or D4 on the bottle. According to the BS EN 204 European standard, these grades are used to classify non-structural wood adhesives and can give an indication of their properties. These D-classes provide a simple way of recognizing the varying characteristics between different glues.

You may be asking yourself, “What does this ‘D’ stand for?” When considering an adhesive suitable for bonding wood, the ‘D’ is an indicator of its durability. Wood glue is therefore categorized into four levels of sustainability by grade, ranging from D1 to D4.

To give a better insight into the differences between these 4 main types, I describe them below:

• D1: Only use in indoor areas, where the temperature only occasionally exceeds 50 °C for a short time, and the moisture content of the wood is maximum 15%.
• D2: Indoor use, with occasional brief exposure to running, or condensed water, or occasional high humidity, provided that the moisture content of the wood does not exceed 18%.
• D3: To be used in indoor areas, with frequent short-term exposure to running or condensed water or heavy exposure to high humidity. Outdoor areas not exposed to weather.
• D4: Indoor areas with frequent prolonged exposure to running or condensed water. Outdoor areas exposed to weather.

What types of wood glue exist?

PVA Polyvinyl acetate

PVA (stands for “polyvinyl acetate”) glue is best known to most woodworkers.
This is the well-known white wood glue that has the thickness of a paste that dries colorless.

To guarantee a good glue connection with PVA glue, it is very important that the glued parts are clamped together well, and that there is always good contact between both parts.

Therefore, PVA glue is not suitable for filling cracks or bonding uneven surfaces.
Below, you will find some of the best wood glues available

Polyurethane

Polyurethane glue normally has a D4 classification.
As I just indicated earlier in this blog, D4 adhesive is a waterproof construction adhesive suitable for wet applications.

In addition, Polyurethane glue is widely used for gluing wood to other materials.

This type of glue is about as strong as PVA glue, but the effect and color are different.
Pay attention when you use this glue because the brown color can leave stains on your wood.

The Polyurethane adhesives are available in one-component and two-component systems, with a second element added to the two-component adhesive to speed up curing.

Polyurethane glue reacts with the moisture in the air, causing it to foam and harden. 
The foam ensures that gaps, cracks, and uneven surfaces are filled. Both parts to be glued must be clamped tightly so that the foam remains in place during drying.

Animal or Hide Glue

Hide glue is the original glue, or predecessor, to all other glues. Although this sort of glue is becoming less popular, it is still utilized in some contexts, such as by instrument builders and traditional woodworkers.

Although hide glue, animal glue, and rawhide glue are different names, they are all the same sort of adhesive.

Skin glue is also a food-safe adhesive that may be used to make cutting boards and other products that come into touch with food, either directly or indirectly.

Cyanoacrylate Glue (CA glue)

Ca glue is growing in popularity in the woodworking industry because to its quick setting time and bright color after curing. If you’re looking for pure strength, though, this isn’t the ideal adhesive.
CA glue is what I use to attach tiny components together or to fast bond parts that need to be glued.

However, there is more to say about CA glue than this, which is why I previously authored a separate article about its usage in woodworking. Please read my article about CA glue if you want to learn more about it.

Epoxy

Epoxy glue is a very strong two-component glue that is also ideal as a filler, because it is liquid and dries very quickly. Epoxy glue is also widely used for the construction of wooden boats.

In woodworking, epoxy will be chosen over a polyurethane adhesive, if the load on the part will be high and extra strong bonding is required.

I wrote a more in-depth article on epoxy glue.
Go check it out to know all you need to know about using epoxy glue for your projects.

8 Awesome wood glue tricks

Tip 1 | Use salt

Do the two parts slide over each other through the used glue during clamping? Prevent this by sprinkling salt over the glue after you have spread the glue over the workpieces. The coarse grain of the salt keeps your workpieces in place better.

Be careful not to use too much salt.
According to glue specialists, salt can react with the glue and change the composition, resulting in a weakened connection.

Tip 2 | Spreading wood glue

To spread wood glue on your workpiece, you can buy different tools, such as rollers. Use an old bank card or membership card to spread the glue. The sides of these cards are perfectly straight and take away excess glue.

Moreover, these cards are easy to clean. Just with a dry cloth and they are clean. However, has the glue dried on the card? No problem! Because many of these cards are made of plastic, the glue will easily come off in 1 movement when it is completely dried out. 

Tip 3 | Cover clamps with wax paper/ foil

When wood glue comes into contact with steel bar clamps or pipe clamps, the moisture in the glue can cause the steel to leave a dark stain on your wood.
Or when you use homemade wooden clamps, the glue can cause the workpiece to get stuck to the clamp after the glue has dried.

To avoid this, place a sheet of wax paper or cling film over the clamps. The protective layer will also catch glue drips, that would otherwise come over your clamps and workbench. Simple and cheap!

Tip 4 | Rub the joint

Do you want the guarantee of a strong adhesive bond? Rub the boards over each other to evenly spread the glue before clamping. By having the glue all over the surface, you are always sure of the best connection between the two pieces you want to connect.

Tip 5 | Tack before you clamp

Wood glue makes boards slippery and can make it difficult for you when applying clamps.
It is quite a task to keep the boards correctly aligned.
In addition to the solution of the salt that I have just discussed, you can prevent the wood from slipping with a few strategically placed brads. 
You can do this before applying the clamps.

Note, however, that the brads are visible with the finished product and do not use brads if you still have to cut into the wood.

Do you want to work with brads?
Lengthen your workpiece and place the brads at the end of your workpiece.
After the glue has dried, you can cut this piece so that no more brads are visible or present in the workpiece.

Tip 6 | Make woodfiller with woodglue

If your project has small cracks, you can make your own wood filler that matches the color of your project. However, keep in mind that using homemade filler can present some issues. You can discover all about these problems in my article, 5 Common DIY Wood Filler Problems When Using It.

Mix some fine sawdust, that you can remove from the sander collection bag, with wood glue into a paste.
For best results, use sawdust of the same wood type as your project. I wrote another article where I go deeper into wood fillers. Be sure to check out that article.

Tip 7 | Use tape

Painter’s tape is never far away from me when I use wood glue. I use it in different situations.

Sometimes I use masking tape along both edges of the joint before gluing.
The excess glue will then end up on the tape and will not leave any stains on the wood.
I apply this trick when I use more expensive woods.

Another good trick with painter’s tape is when you need to glue corners. Place the 2 boards with their 45-degrees cuts against each other.
Connect the 2 boards at the bottom with tape, place the wood glue on the 45-degree cuts, and then simply fold the 2 boards together until you got your 90-degree corner. You can also use painter’s tape to keep newly glued pieces in the correct position.

Tip 8 | Thickening wood glue

As wood glue ages, it tends to thicken. Because the glue is thicker, it is more difficult to use for gluing.
Many don’t know but you can thin this glue again.

Adding 1 or 2 drops of vinegar to the glue will make it easier to process. However, be careful not to use too much vinegar because it can change the composition, resulting in a weakened connection.
For a more in depth article on this topic, I suggest you should read How to Thin Wood Glue – 4 Quick & Easy Fixes

With these 8 tips you can get started to glue wood. In my article how to use wood glue, you can find the proper way to use this type of glue. Avoid commonly made mistakes and read this article first.

How to store wood glue?

Most glue manufacturers provide their products with an official shelf life. The stated shelf life of wood glue is usually one to two years.
They use this shelf life to limit liability in the event that poor storage conditions cause product failure.

However, the expected shelf life of many types of glue is higher than those few years.
When you store wood glue under optimal conditions, it can last 10 years or more.

What are the best conditions to store wood glue?

• Always keep the wood glue in the original packaging.
• A dry, cool cellar is the ideal place to store wood glues.
  You may be able to extend the life of your glue if you have room for it in your refrigerator.
  I can already hear you thinking: how will I explain that to my partner.
• Do not try to freeze the glue.
  If it does happen, most wood adhesives are designed to withstand at least five freeze/thaw cycles.
  The glue forms, gels with each cycle. Mixing these gels will break these gels down again, but the gels will be more difficult to disperse with each subsequent freeze/thaw cycles.
• Heat can also cause the polymer to clump and gel.

In my article How to Store Wood Glue for Optimal Performance? 3 Quick Tips I go a lot deeper into this topic. Be sure you read this article to get the most out of your wood glue.

How do you know if your glue has gone bad?

To know whether your wood glue has gone bad, there are a few things you can do. I will list them shortly below, but If you want to go deeper into this, you have to watch my article How To Tell If Wood Glue Is Bad? 4 Tips To Avoid Disastrous Joints. There you can learn all about this.

• Take note of the aroma when uncapping the bottle of glue.
• Check the color and texture of the glue.
• Consider the expiration date and how it was stored.
• Observe how the glue dries and sets.
• By understanding these key indicators, ensure that your wood glue is always in good condition and ready to use.

wood glue drying time

Because there is a lot to say about this topic, I wrote a complete article about it. All the info you can find in the article, — “How Long Does Wood Glue Take To Dry? 5 Tips You Should Know!” — will be of great value the next time you start working with wood glue. Be sure to check out that article!