Most people think of epoxy adhesives as the most powerful type of adhesive. In many cases that's true, however, before using epoxy adhesives it's important to understand what they are and how they work. Here are the basics you need to know about epoxy adhesives.

"Epoxy" is not a single catch-all term. There are many different epoxies that vary in strength, their curing time, as well as their physical properties once cured. That means some epoxies are meant to bond to certain types of surfaces such as plastic, fiberglass, ceramic, metal, etc. and others may not work as well on the same type of surface. That is why it's important to read the manufacturer’s instructions on any given epoxy you may be using.

There are two-part and one-part epoxies. Since epoxy adhesives literally have to undergo a chemical reaction to cure and bond, the most common type of epoxy involves two components. Typically both have a paste or glue-like consistency. They must be mixed together in the proper ration quantity and as they mix they begin to cure immediately. Some epoxy adhesives are available as a single component type, which can simply be applied right out of the tube or container. While the single component epoxy may seem more convenient to use, they also require high temperatures to cure and thus are less common in most applications. Two component types can bond at room temperature very quickly.

Once you mix or apply an epoxy it is immediately undergoing a chemical reaction. It's important to plan out your work before you open or mix the epoxy adhesive. Once it is mixed you have limited time to apply it and put everything in place before the reaction is complete and the epoxy cures, hardens and binds. Hardened epoxy is very difficult to remove and often must be sanded away. Epoxy curing times can vary from a few minutes to an hour, so it's important to use it promptly.

Not all epoxy adhesives are waterproof. People commonly think of epoxy as a waterproof substance, but this is not always the case. Many epoxy adhesives can weaken if submerged in water or exposed to moisture regularly. While the epoxy will not dissolve in water, it may lose its adhesion and pull away from the bonded surface. That means they are not good for caulk unless specifically indicated for that purpose. There are specialty waterproof epoxy adhesives available and will perform excellently even completely underwater.

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