We get many questions about woodworking glues. There is such an array of glues available these days, it's no wonder that people can get confused on what to use. We understand that having at least a basic knowledge of what is available is important in order to get the best results we can.
Of course the other issue is that many glues overlap in their uses so often there is a variety of choices and a variety of brands to choose from as well. In this article we will deal with only some of the basic glues, when to use them and for what applications. There are many, many other glues we won't be touching on that may also be suitable for different applications and if you are in question, the internet is a rich resource for information on glues, especially if you want the details on a particular glue, where it should be used, it's cleanup requirements temperature requirements and of course it's PSI or holding strength as a glue.
PVA Glues, or Polyvinyl Acetate glues are easily the most common glues used in woodworking with natural woods. The reason for this that this glue has been around for 100 years and gives consistently good results when uses as it should be. It cleans up easily with water, or you can leave it to dry and harden and clean up later, and ....
The glue has a good shelf life and will last for years in normal room temperatures. This glue is primarily for natural woods, especially gluing long grain to long grain which is much of what woodworking is about. These glues normally economically priced and are the staple of most woodworkers.
Polyurethane or PU Glues are also an excellent glue, but are more recent to the market after invention in Germany in 1937. Gorilla Glue has done an excellent job of marketing this brand of glue and is well know world-wide. PU glues are NOT water clean up, instead requiring alcohol making them a bit less friendly. Most people simply wait for these glues to dry and clean up any squeeze out after the fact, which in most cases appears as a foam along the glue line. PU glues work best in the presence of a bit of moisture so if your wood product is dry, it is best to dampen the surfaces with water before applying the glue, and thereby getting a better end result. PU glues are also widely used in woodworking but being a bit more expensive than PVA glues, are not a widely used. One of the drawbacks of PU glues is that once the sealed bottle is open and exposed to air and the moisture in the air, the glues begin to slowly harden and with in weeks, or even days, depending on the environment, the unused glue in a bottle can be hard as rock and unusable. For this reason PU glues come in a variety of sizes and it's best to purchase just what you need at the time. PU glues are great for working with plywoods and other many made woods, especially if there is a need for some edge gluing such as in cabinet making where the carcasses are made of MDF or plywood.
Hot Melt Glues are often considered as a "hobby" glue, but because it is a handy, easy to use and quick setting glue it does have a use in the workshop in a variety of places. Hot melt glues come in the form of waxy looking stick which is the glue that is activated by heat in a special gun applicator. For temporary and very quick gluing this is a very hand method, especially if you are constructing something and need a third hand to hold something, very often hot melt will come in handy for this, as well as for certain jigs and other quick assemble workshop uses.
Epoxy Glues come in 2 parts, the glue and the hardener and are mixed together in equal quantities. They do come in a variety of "open times" but 5 minute epoxy seems to have become a standard phrase, meaning the glue hardens and cures in 5 minutes. Then nice thing about epoxy glue is that it is not just for wood or wood substitutes, it can also be used for ceramic, rock, metal, some plastics and a variety of other materials. Like PU glues, it does NOT clean up with water, and when it dries and hardens, it is like rock, so only mix what you need and try to avoid squeeze out and if you get some it is best to try to remove it with a dry cloth as sanding this material is tedious. The 2 containers of epoxy do have good shelf life but are expensive to purchase.
Cyanoacrylate or CA glues as they are called are well know to woodturners who make pens. To most of us CA glue is also called Crazy Glue and often comes in quite small quantities owing to it's high purchase expense. In many ways it has the similar properties to epoxy glues but with CA glues you can apply the glue and simply wait a few hours for it to harden, or you can use an accelerator spritz on the glue which makes it harden instantly. This glue will bond most surfaces with the exception of a some plastics and rubbers.
Hide Glues have made a bit of a comeback in recent years and are now being made commercially. In the past a woodworker had to make his own and since this product has been around for hundreds of years, it is pretty basic. The advantage with hide glue is that with a bit of heat you can easily un-glue something which is perfect for antique furniture and some musical instruments like violins that need to be taken apart and re-glued every couple of hundred years or so, or to fix or replace wear or damage. Nice to have a product like this available but not a common glue to find in a woodworking shop, unless you are a luthier.
Out Door Glues - Generic
For the purpose of this article, we'll say there are two basic kinds of outdoor glues, the PU or Polyurethane glues and glues similar or modified PVA glues. The difference between them is this, polyurethane glues dry hard and waterproof. There is little or no give to a PU type glue, basically it will break before it bends of gives. This means that as an outdoor glue it is perfect in situations where there would be little or no movement. The other type of PVA styled glues are of a consistency that never really dries hard. They are always a wee bit soft. The advantage of this is that for wood projects outside where there are changes in temperatures and weather conditions which are making the wood constantly expand and contract, these type of glues are great because they have some give to them while still adhering to the wood.
Other Glues .... there are many more glues to talk about like construction adhesives and other specialty glues. The best source of understanding these glues is the internet and knowing what it is you are wanting to glue together. Once you know this, there will be a world of glues for you to choose from
Copyright - Colin Knecht