Epoxy is a widely used adhesive and filler that adds a strong, waterproof layer to wood and other surfaces. Whether it’s used on the countertops in your kitchen or the underside of your sailboat, epoxy is a difference-maker in many situations by increasing a surface’s durability and keeping water damage at bay.
Available in different forms—including liquids, glues, gels, putties, and resins—epoxy is unique compared with other adhesive products because some types require the combination of two individual components. Together the two components trigger a chemical reaction that causes the epoxy to harden.
Epoxy Resins
When most people think of epoxy, chances are they think of two-part resins, which calls for mixing these two parts: a) the resin itself, and b) another liquid known as the hardener. It’s important to note that the formula must be mixed at exactly the ratio recommended by the manufacturer. Failure to do so will cause the resin to not harden properly.
While most brands are non-toxic, there are still certain precautions that should be followed when working with epoxy resins. Because epoxy can irritate the eyes and skin, always work in a well-ventilated area and wear safety glasses and gloves. If you use epoxy frequently, you might also consider purchasing a respirator mask. Also, unused epoxy resins should always be disposed of according to manufacturer recommendations.
Another note relating to epoxy products: Different epoxies have different curing (or hardening) times. There are even one-minute epoxies on the market. But the general rule of thumb is: the longer the cure time, the stronger the bond.
Prepping Your Surface
To prepare a porous surface such as wood for an application of epoxy resin, you must first apply what’s known as a skim coat. This is sometimes called a base coat or seal coat.
Here’s how to prep your surface for the initial coat. Start by thoroughly cleaning your surface and sanding it down until it is smooth and dust-free. While sanding is not required, some experts recommend a light sanding with 220- to 320-grit sandpaper to help increase the adhesion of epoxies. If you’re working with tile, you’ll also want to clean the surface with 91% isopropyl alcohol.
Then, mix the recommended amount of resin and hardener using a wooden stick and apply a very thin coating using a brush or even a squeegee. If you’re working with a surface that’s roughly 50 square feet, you only need about a quart of epoxy for your entire skim coat.
Note: This layer should be very smooth—if you notice any air bubbles, pop them with a toothpick. The purpose of this initial layer is to prevent the next layer (sometimes called the “flood layer”) from seeping into the wood or other material you are sealing. The skim coat allows for a better overall seal when you apply the second layer.
You’ll want the skim coat to dry for at least six hours before applying the next layer.
Also, keep in mind that the temperature of your work area matters when working with epoxy. It’s been found that most epoxies bond or cure best at temperatures of 60°F and above. While some products are specifically designed to cure at lower temperatures, working with these products typically requires specific steps to allow them to bond.
Applying Additional Layers
You’ll need to apply at least two layers of epoxy to achieve a proper seal. In some cases, you can add a new layer over wet epoxy that has cured enough to handle the weight of another layer—this creates what’s called a “primary bond.” Unless you are experienced working with epoxy resins, it is usually recommended to wait until the surface is dry and completely cured.
Before proceeding with a new layer, check for something called “amine blush.” This is a wax-like film that sometimes occurs during the curing process and can negatively impact the next layer of bonding. If you notice this occurrence, wash the surface with water and use an abrasive pad to gently scrub. Then, dry with paper towels and sand out any glossy areas with 80-grit sandpaper. The surface should now be ready to accept the next epoxy layer.
The second layer is usually referred to as a “flood layer” because it is applied by pouring epoxy on the entire surface. (If you’re sealing a table or other piece of furniture, be sure to place cardboard or another disposable floor covering down before this step.) Start at one side and cover the entire surface, going back to fill in any empty spots.
If air bubbles appear, use a heat gun or blow torch to slowly and carefully remove them. Move the device back and forth in a steady motion and set it to medium heat to avoid overheating the epoxy.
The surface should be dry in about 12 hours. However, you shouldn’t place anything on top of the surface for at least three to four days to be sure it is completely cured and ready for use.
Product Compliance and Suitability
The product statements contained in this guide are intended for general informational purposes only. Such product statements do not constitute a product recommendation or representation as to the appropriateness, accuracy, completeness, correctness or currentness of the information provided. Information provided in this guide does not replace the use by you of any manufacturer instructions, technical product manual, or other professional resource or adviser available to you. Always read, understand and follow all manufacturer instructions.