I received an email this morning asking a very basic, open-ended question: “What is the best adhesive to bond hardboard to plywood?” My quick answer was to use a yellow woodworkers glue. I also mentioned polyurethane glue as a good option for bonding just about anything.
But then I decided to look into it a little closer and found a good article all about choosing and using glues in Woodsmith Issue No. 134.
Yellow and White Glues. The article is all about finding the best glue for the job and at the top of the list were the yellow and white PVA (polyvinyl acetate) glues that every woodworker knows about. They’re easy to use, clean up easily, and they form a strong wood to wood, or wood to plywood bond. Some are good only for indoor use and some (like Titebond II and III) can be used outdoors.
Hide Glues. If you want to take a joint apart someday, then hide glue may be the best choice. Hide glue cures very strong, but a little bit of steam directed at the joint allows it to be pulled apart. Traditional hot hide glues are kind of messy and you need a special glue pot to use them. That’s why I like to use a ready-mixed liquid hide glue from Titebond, at right. An additive keeps the glue liquid inside a sealed bottle, plus it has a longer set up time.
Polyurethane and Resorcinol Glues. If you’re building a project that will spend any time outdoors, you may want to choose a “poly” glue. Polyurethanes, Gorilla Glue and Bolder Bond are two popular brands, cure by reacting with moisture so you use less glue because you’re only applying it to one side of the joint. Then you spray a light mist onto the second workpiece to activate the glue. The glue cures as the water evaporates.
Resorcinol glue is a favorite of boat-builders because, even if it’s submerged in water for a long time, it won’t dissolve. The drawback to resorcinol is that it’s a two-part adhesive, so it needs to be mixed beforehand.
Epoxy, Instant Glue, Spray Adhesive and Hot Melt Glue. Finally, there is a full line of specialty glues that I like to use now and then. Epoxy is great for joining different kinds of materials together. It provides an extremely strong bond, but it’s another two-part glue (a resin and a hardener) that needs to be mixed together.
Instant glue, also called “crazy” or “super” glue, is great for filling small cracks and for replacing small pieces that chip off. Be careful though. If you aren’t planning on using much, be sure to buy a small bottle because they only last about six months after they’ve been opened.
Spray adhesives come in aerosol cans and I use them most often to attach a piece of paper or fabric to something. And hot melt glues can be used for any job that you don’t want to be joined together permanently. They provide a temporary bond that’s perfect for jobs like applying a pad to the jaws of a pipe clamp.
So there you go. I’m sure I’ve left out a few good options for joining hardboard to plywood in this quick primer. If you have any suggestions for how you do it, please pass them on in the comments box below. And if you’re interested in more information on gluing basics, you’ll find a good article covering it at PlansNow.com at a very reasonable price.