Just how do you choose the right wood glue, you ask? Many people new to woodworking are surprised at the strength of today’s wood glue. In fact, when using the right wood glue for the application, the cured wood glue joint will be stronger than the wood that’s being joined. In other words, it’s more likely the wood will break before the wood glued joint fails.
So, what’s the right glue to achieve these results? Well, it depends on what wood you are gluing, and how the finished project will be used. With this in mind, let’s take a look at some of the most popular types of wood glues on the market.
There are five main types of wood glue used in woodworking:
- PVA (Poly-vinyl acetate)
- CA (Cyanoacrylate)
This blog will first focus on PVA wood glue, as this is by far the most prevalent type of glue used in woodworking. Then the four other wood glues will also be touched upon, followed by a list of definitions that help in your wood glue shopping.
Poly-vinyl acetate (PVA) wood glue is perfect for basic woodworking projects. It’s inexpensive, non-toxic, readily available, cleans up with water, has a modest tack (allowing you to reposition workpieces during assembly) and, once cured, is very strong.
Tite-bond offers a full line of PVA wood glues. Gorilla Glue, known mainly for polyurethane glue, also has a PVA wood glue. Selecting the right PVA glue totally depends on a variety of factors.
- Tite-Bond Original Wood Glue sets quickly, has a strong initial grab, but is indoor use only.
- Tite-Bond II not only sets quickly and has a strong initial grab, it is also water resistant and can be used indoors or out. What’s more, it’s approved for indirect food contact (such as cutting boards, bowls, etc.)
- Tite-Bond III is waterproof, sets slowly, making it ideal for more complicated glue-ups, and has a lower application temperature which is good for cold workshops.
- Gorilla Woodworking Glue is similar to Tite-bond II. It can be used indoors and out and is also approved for indirect food contact. (Note: do not confuse this wood glue with their popular polyurethane glue.)
The wood glues listed above cover the vast majority of woodworking applications. However, there are a few specialty PA wood glues that are helpful in certain situations.
Specialty Wood Glue
Need a longer assembly time. Titebond Extend Wood Glue is a slower setting version of Titebond Original Wood Glue. It is particularly useful in complex operations such as curved railings and other assemblies that require more time to align. It has a full 15 minutes of open assembly time. Not intended for exterior use or where there is moisture.
Working with dark woods. Titebond II Dark Wood Glue is a dyed-version of Titebond II Wood Glue. It helps hide joints in darker woods such as walnut. It provides a strong initial tack and fast speed of set to reduce clamp time.
Concerned about glue running or dripping. Titebond No-Run, No-Drip Wood Glue helps prevent wood glue dripping and running because it is a thick, fast-drying wood glue. It is ideal for finish trim, crown molding, baseboards, window casings and other applications requiring a professional-strength, no-run wood glue. It provides a strong initial tack and fast speed of set, yet allows realignment of working pieces.
Cyanoacrylate (CA) glue is great for small repairs, particularly when carving or turning. This wood glue dries quickly and forms a stiff, plastic-like bond. The liquid form of this wood glue can often run, but this wood glue is also available as a gel that stays in place better. Gorilla Super Glue and Titebond Instant Bond Glue are two good examples.
Epoxy comes in two parts: a resin and a hardener. Both are liquid, but when mixed together a chemical reaction occurs that causes the epoxy to harden. Epoxy has the advantage of being waterproof and does a good job filling gaps in wood. Most other wood glues will not hold well if there is a gap between the pieces of wood that you are gluing together. Some epoxy formulas take a while to cure, others will cure in as little as five minutes. In general, the longer it takes for the epoxy to cure, the stronger the bond will be, so patience will be rewarded.
Polyurethane glue is very durable and is often referred to by the trade name “Gorilla Glue.” However, Titebond also makes an excellent polyurethane glue. This type of glue cures in the presence of water, requiring you to wet the two mating surfaces before applying the wood glue. It bonds well to wood and many other materials, including plastic, metal, fabric, and others. As it cures, this glue tends to expand. And since it is hard to remove, make sure any glue squeeze-out is quickly removed. Polyurethane glue is a great choice for outdoor furniture applications and places where you need a very strong bond.
Yes, this glue comes from animal hides. Hot hide glue is made by heating granules of hide glue in a pot with water. As it heats, the glue liquefies, and as it cools, it becomes solid. The biggest reason for hide glue’s popularity is its reversibility. If you apply heat to the joint, the glue will loosen. Recently, Tite-Bond developed a liquid hide glue that can be used at room temperature. This new glue has most of the same properties of hot hide glue, and has a longer open assembly time.
Wood Glue Features To Consider
Bond Strength: The unit load applied in tension, compression, flexure, peel, impact, cleavage or shear, that is required to break an adhesive assembly with failure occurring in or near the plane of the bond. Typically reported in pounds per square inch (psi).
Clamp Time: The period of time that the substrates being glued together need to remain clamped.
Closed Assembly Time: The period of time between putting the glued substrates together and clamping. This time allows for moving the pieces into their final position.
Chalk Temperature: When glue dries, the loss of water pulls the adhesive particles together with enough force to form a continuous film. If the drying temperature is below a critical point, water evaporation is not sufficient to pull the particles together, leaving them in the joint. The dried film in the joint will appear whiter than normal. This is known as “chalking” and the critical temperature is the “chalk temperature.” When chalking occurs, the glued joint loses strength and could result in a failed bond.
Freeze-thaw Stability: The ability of a product to remain usable after it has been frozen and thawed. Some wood glue will have a “cottage cheese” look after freezing. If this happens, shake/stir glue to original form.
Open Assembly Time: Period of time between initial glue application and putting the substrates together.
Speed of Set: The rate at which an adhesive can build strength.
Squeeze-out: Adhesive pressed out at the bond line due to pressure applied on the substrates.
Starved Joint: A joint in which there is not enough glue for a proper bond to form.
Storage Life: The period of time during which a packaged adhesive can be stored under specified temperature conditions and remain suitable for use.
Tack: The property of an adhesive that enables it to form a bond of measurable strength immediately after the adhesive and substrate are brought into contact under low pressure.
Total Assembly Time: The period of time between the initial glue application and clamping.