In the world of woodworking, adhesives play a vital role in joining pieces of wood together to create sturdy and durable projects. Adhesives are a large part of what takes the 2-dimensional pieces and turns them into a 3-dimensional product. With a wide range of adhesives available, each with its own unique properties, it can be challenging to determine which type is best suited for a particular woodworking application. Here we explore different types of adhesives commonly used in woodworking, their applications, and provide examples of how they are used in the woodworking shop.
PVA (Polyvinyl Acetate) Glue:
PVA glue is a popular choice in woodworking due to its ease of use, versatility, and affordability. For example it is available in both white and yellow variants, with yellow being more suitable for outdoor projects however they are both water soluble overtime. The water solubility of PVA glue however does allow you to use water to slightly thin the glue when in use. This is in many cases a bonus when working with the glue and provides some additional flexibility when working with it.
PVA glue is commonly used for general assembly, joinery, and veneering. Its relatively long open time allows for adjustments before the adhesive dries, making it ideal for complex assemblies. Examples of how we use PVA glue include joining boards to make panels for larger projects and we also will use it combined with sawdust to fill in gaps in panels or pieces of wood that are not completely smooth or have knots we’d like to fill in slightly.
Cyanoacrylate (CA) Glue
CA glue, is a fast-acting adhesive that bonds quickly and strongly. This is essentially your garden variety “super glue”. It can bond various materials, including wood, metal, and some plastics, making it a versatile adhesive in the woodworking shop. Its ability to cure quickly is extremely helpful on projects where clamping the pieces together for an extended period of time is not possible and the quick dry time is favorable.
It is often used for bonding small projects, filling cracks and gaps, or reinforcing joints. Examples of CA glue in use include repairing split wood, securing inlays or small decorative elements, and assembling delicate projects. For oddly shaped projects in our shop we love to utilize glue options other than the standard PVA glue to ensure they are securely attached!
Epoxy resin is a two-part adhesive system that consists of a resin and a hardener. It is known for its exceptional strength, durability, and ability to fill gaps. Epoxy is commonly used for bonding large surfaces, laminating wood, and filling voids or imperfections in wood. One of the many reasons woodworkers might choose to use an epoxy resin over other types of adhesives is the waterproof quality that it has that exceeds many of the other options. This makes the resin ideal for items that commonly find themselves in damp or wet areas.
To use the resin you combine the two parts in a disposable vessel and mix them together to create the mixture you end up using. Loctite in particular creates an option that is combined without you needing to worry about the ratio which is extremely helpful! Simply push down the plunger and both compounds are mixed in the perfect ratio. Once the resin is mixed, you do need to stay on your toes as you have a limited amount of time to work with it before it hardens. Some styles have a working time of as little as 1 minute with others having a working time closer to 5 minutes. Almost no resin adhesives have a longer working time than 1 hour or so after the hardening agent is mixed in.
Polyurethane glue is a versatile adhesive that works well on a wide range of materials, including wood, metal, and plastics. It was first brought to the US by the Gorilla Glue company as a new adhesive option. Similar to how an epoxy resin requires a curing agent, the water allows the glue to cure. It expands as it cures, filling gaps and creating a strong bond. This expansion requires wood pieces to be clamped when using this glue to ensure they do not move while the glue cures. A unique feature of polyurethane glue is that it requires moisture to cure.
Polyurethane glue is particularly useful for projects where a waterproof or weather-resistant bond is required. Examples of polyurethane glue in use include joining outdoor furniture, repairing outdoor structures, or joining two pieces of wood especially when those two pieces include end grain. Polyurethane glue is perfect for end grain pieces which typically absorb the glue used on them making a strong bond difficult. Polyurethane glue helps ensure a strong bond due to expanding as it cures which allows for the end grain to be filled by the glue and still make contact with the other piece.
Hide glue, traditionally made from animal products, has been used for thousands of years as an adhesive especially for wood. Hide glue is commonly used in furniture restoration, instrument making, and other fine woodworking applications that have a longer history and smaller parts.
It offers several advantages, such as reversibility with the help of some warm water, excellent adhesion, and compatibility with non water based finishes. The open time for the glue also varies once it is mixed up depending on the brand. However, it does require additional prep time as it must be heated with water in a glue pot before application due to coming only in dry forms of either ground , flakes, or pearls. It will then need to be applied while it is still hot with a brush. This means that the temperature of both the glue and your project must be taken into consideration before applying it.
Adhesives are indispensable tools in the woodworking shop, enabling woodworkers to create strong and durable projects. Understanding the different types of adhesives available and their specific applications is essential for achieving successful bonds and ensuring the longevity of your woodworking projects. Whether you’re assembling furniture, repairing split wood, or creating unique designs with epoxy resin, choosing the right adhesive can make all the difference in the quality and longevity of your woodworking creations. So, next time you embark on a woodworking project, consider the type of adhesive that best suits your needs and enjoy the satisfaction of crafting something remarkable.