Gluing the Difference

Gluing the Difference

If there is one thing in woodworking besides wood that people use no matter what kind of woodworking they do, it has to be wood glue. Glue has been used to adhere pieces of wood together for hundreds of years.

The most common wood glues are polyvinyl acetate (PVA), also known as “white glue” and “yellow glue”. Each of the glues works in the same manner, but has a few different characteristics. White glue slips more during assembly while yellow glue has more of an instant tack. Both provide a strong wood to wood bond, but will not adhere to non-porous surfaces like ceramic and plastic. PVA’s are great glues to use with other fasteners like nails, screws, dowel pins and biscuits. Because of the plasticity, there can be glue failure and one should not expect the glue joints to last more than 15-20 years. If you’re building an heirloom piece, this may not be the glue that you should use. For small items, craft items and pieces that will contain extra fasteners or special joints PVA glues are the perfect match. They are easy to use, easy to clean up and take a lot of the work out of woodworking.

Some examples of PVA glues are Titebond Original Wood Glue, Elmer’s Carpenter’s Glue and regular Elmer’s Glue.

A special thing to consider is the “water resistant” PVA glues. These will repel and withstand water better, but are not waterproof. Over time the glue joint will fail. A much better alternative is waterproof glue that will withstand immersion in water.

Application of PVA glues is relatively simple. Apply the glue to the surface and spread evenly across it. There are all kinds of tools that are available to help with this task; my preference is my fingers since PVA glues are cleaned up easily with water. Once the glue has been applied to each of the surfaces being glued together, place the surfaces together and clamp. This may also be accomplished with screws, nails or other fasteners. PVA glues may be taken out of the clamps after as little as an hour, but should not be worked immediately. At that point the glue has not cured yet. Make sure that the wood is not under any stress. After as little as 4-5 hours, the wood articles can be worked. For best results, let your glue set up overnight.

Heat also has an effect on PVA glues. PVA glues should not be used where there is exposure to heat. Remember, they are plastic based and plastic becomes elastic with exposure to heat. Your glue joints will do the same thing.

Polyurethane glues are your best waterproof glues available. The polyurethane glues will adhere to wood, metal, most plastics, ceramics and stone. It does not dry like regular PVA glues. Polyurethane glue actually chemically reacts with moisture. The chemical reaction causes the glue to expand. If the material is dry or has an oil base, like exotic hardwoods, spraying a light mist of water on the material will help the curing process. It is very important to use appropriate clamping when working with polyurethane glue. If the work piece is not clamped properly, the glue with actually push the joint apart as it cures. Some disadvantages of polyurethane glue include the workability and stickiness. If you’ve ever tried to use polyurethane glue without hand protection, you have probably wound up with sticky fingers, had problems wiping it off and finally ended up with stained fingers with a not so easy to peel off film on them. There are definitely areas that require glue like polyurethane glue, but consider your options when working with it. The most popular polyurethane glue is Gorilla glue.

Urea Formaldehyde is one of my favorite glues when it comes to laminations or needing glue in applications where you don’t want any slipping or spring back. One of the more popular brands is Unibond 800. Urea Formaldehyde is also referred to as “plastic resin glue”. The best characteristics are its long open time and it dries fast depending on how it is mixed. The glue is a two- part glue that is mixed together. The largest issues with urea formaldehyde are its odor and potential health issues from the fumes when mixing and applying. Make sure the room you are working in is properly ventilated. Urea Formaldehyde is great for large projects like kitchen tables, veneering, laminating rockers and bending projects where spring back is a concern. While fairly new on the market, the lack of elasticity will make this glue that will be around for a long time to come.

Cyanoacrylate glue also known more commonly as “Super Glue” is used mainly for small repairs especially in woodturning. It works on dirty, oily or similarly soiled surfaces and bonds faster than other glues. It is a great glue for wood, nylon, vinyl, plastics, acrylics, leather, ceramics, aluminum metal and other surfaces. Super glue is great mostly for small projects and does not have the power to glue major wood joints together. I use it mostly for small projects or bonding most any type of material to wood. An advantage is its quick setting power. This can also be a disadvantage if you are not quite ready with your project or have your fingers in the wrong place. Acetone will quickly clean and dissolve super glue. It is a good idea to keep it on hand or remember that acetone is also in finger nail polish remover.

Hide glue is an old standby and was a ubiquitous staple in woodworking shops for centuries. Hide glue can still be found in many shops and is used quite often for musical instruments. It is reasonably easy to work with and sets up fast. Hide glue sets as the gel cools, leaving a secure joint in a matter of minutes. It is also the easiest to fix. Hide glue normally comes in a granular form and is mixed with water then heated to a liquid consistency. The glue is then applied to the joint, the joints are firmly pressed together and in a matter of minutes, a good glue joint is created. Hide glue is one of the easiest to fix while some other glues are almost impossible. If you have an antique it is more than likely glued with hide glue. This is the glue that I have used on several scroll saw pieces. It will stand the test of time and is easy to work with. If you are looking for a time honored method of gluing, using hide glue should be high on your list.

Epoxies are something that we all need to use from time to time. One of my favorite uses for a two part epoxy is using it as filler. Simply create a small pile of sawdust using 320 grit sandpaper. Place the wood particles of sawdust on a piece of paper, measure out equal amounts of the two part epoxy about the size of a dime and start mixing the three together to a smooth consistency. Fill any holes with the mixture and sand after it has set up. Five minute epoxy is usually used for filling. Longer epoxies are an excellent choice when adhering wood to metal or other substrates. There are tons of different combinations that are available depending on your project and materials used.

There are many other types of glue available from contact cement to hot melt glues. These glues are not recommended for most woodworking applications. Hot melt glue and contact cement are only a temporary fix and will not provide the strength and longevity to a glue joint. Many times there have been references to using contact cement with veneers. If you are building an heirloom and taking the time to complete a tedious project, glue the project together with something that will last. Contact cement is elastic and will break down over time; it is also hard to repair.

For as many different kinds of glue made there are also a variety of methods to clamping your work together. With small projects we struggle to figure out how to clamp pieces properly. The traditional methods of huge clamps just won’t work. Keep these simple ideas in mind when clamping up your next project.

  • 1.Tape can be useful. I recommend using 3M painter’s tape with a seven day mask. The tape has an elasticity that others do not and can easily be removed from your project when you are finished clamping. The tape can be formed to any surface and makes a complex job very easy. I have been using this method for years, especially on scroll saw projects and marquetry. To make the tape work as a clamp, adhere the tape to one piece, then pull the tape across to the second piece keeping it very snug. This will pull your pieces together to create a nice joint.
  • 2.Rubber Bands don’t hurt. Many people find rubber bands very useful in the clamping process. A small multisided piece can be banded together until the glue joint are solid.
  • 3. Clamps come in all kinds and sizes. Mini quick clamps are a favorite and work well when putting models together like many scroll sawn clocks.
  • 4. Vacuum pressing is another option and works great for veneering, marquetry and laminations. It has its limitation when gluing odd size pieces.
  • 5.There are many other techniques and ideas for clamping. Just be resourceful and think about the clamping items you have available and test them on a dry run of your project.

This article was provided by Cindy Kryshak. Cindy has been spent over 25 years as a woodworker and designer in the woodworking industry. She holds a Master’s from Marc Adams School of woodworking and has lectured throughout the United States including lecturing for the Woodworking Shows.