Woodworkers use several types of glue; the choice of which one to use depends on the nature and complexity of the task at hand. At times you might even use more than one type of adhesive on a single project. It is important to understand the strengths and weaknesses of each adhesive.
Here are some of the most commonly used in a woodshop.
Hot hide glue– Hide glue, made of animal proteins, is the oldest type of adhesive used in woodworking. A small amount of glue pearls or flakes is soaked in water for about 30 minutes before heating in a water bath to about 145 degrees, until it turns to a syrupy texture.
For veneering, the glue is applied with a brush while warm and then firmly with a veneer hammer. When the glue cools, a bond is achieved. Hide glue is also used where clamps are not realistic; this is called a “rubbed joint” and is often used for corner blocking, and for the knee block on a cabriole leg construction.
Liquid hide glue– Sold as Old Brown Glue, this adhesive is similar to traditional hot hide glue- but comes ready to use in liquid form. The addition of Urea keeps the glue liquid at room temperature and also extends the drying time. The advantage is that it has a longer open time (about 1 hour) than hot glue. Like traditional hot hide glue, it is reversible with heat and warm water and does not stain the wood or influence the finish. This adhesive is used for traditional glue-ups (such as case work and chairs), requiring clamps or a large press and is not suitable for hammer veneering.
Yellow glue– Also known as PVA (polyvinyl acetate), this is the most common glue used for woodworking and is most suitable for the assembly of porous materials, such as wood. It cleans up easily with water. And although it can be used for rubbed joints, the strongest results are obtained by using clamps or a press. At PFW we also use it for an unusual technique that involves a common household iron (see Serpentine table and Modern coffee table projects).
It works by cross-linking, meaning that this water based glue soaks into the surface of both members being joined, and then dries by evaporation. When dry, the glue has basically dried on itself while beneath the surface of the now joined pieces of wood. Typically, this joint is stronger than the wood itself.
At PFW we also use it for an unusual technique that involves a common household iron. This is the method employed on both the Modern Veneered Coffee Table and the Serpentine Hall Table.
CA glue – Also known as cyanoacrylate or “super-glue”, this adhesive is great for quick, spot repairs that are non-structural and otherwise impossible to clamp. It’s available in several different viscosities (thin, medium and thick). By spraying the glue with an activator, such as hexane, the glue will dry immediately so that your work may proceed without delay. It is also handy for closing a minor cut, but do not use the activator on human tissue or a serious burn will be the result.
If you run into a knot that could be tighter, or some punky wood, use CA glue to “freeze” the problem. For this usage, the thin CA glue is best as it is thinner than water, and soaks into the wood quite deeply.
“Unibond 800”– This brand of urea resin glue is ideal for bent laminations, laid up in gluing jigs, and for veneer panel work, glued up in a vacuum bag. The proportion of the 2 parts of this adhesive can be varied to control the amount of open time, which on a cool day can be up to about an hour. It is also waterproof, although not rated as such. Total Beginner 3 leg arch