Several types of resins are used in the countertop industry. The resins, when mixed with a catalyst "hardener," set up after approximately 20 minutes, but can vary depending on the amount of hardener used. These compounds are commonly used for setting seams in stone counters or providing a glossy, protective finish to concrete countertops.
Stone countertops, commonly fabricated from slabs of material such as granite and marble, are cut from slabs. Because the material is very heavy, the countertops are cut into pieces that are more manageable. This produces seams where the pieces join. Epoxy resin is used to fill the seams and smooth the joint between them. It is also used to fill voids or imperfections in the stone.
Concrete countertops are coated with epoxy resins to provide a protective layer and enhance their appearance. The resins used for concrete counters are different from those used for stone. Both the resin and hardener are more fluid, which allows the material to flow over the surface, which in turn produces an even coat. The epoxy is applied by pouring it over the concrete surface and spreading it with a plastic spatula or stiff piece of paper.
The most important thing when mixing resins for countertops is to carefully read and follow the manufacturer's instructions. The working life and mixing ratios for the resins vary greatly among manufacturers. The time you have to work with the material before it sets is affected by the amount of hardener mixed with it. Too much hardener causes the resin to "kick," or set too rapidly, which may not leave you enough time to apply it properly. If you do not mix enough hardener, the material can fail to set or result in a tacky surface.
There are several things you can do that will help you achieve a professional result when working with resins. Mix only as much material as you can work with before it sets. Countertop seams require only a small amount of resin, about 1/4 cup. Mix the resin and hardener on a piece of cardboard and apply it to the seam using a shim, razor blade or putty knife. Once the material dries, use a straight razor to shave off excess material to provide a smooth joint. When coating concrete counters, you must mix enough material to coat the entire surface before it starts to set. It is helpful to have an assistant during the coating process who can mix the material while you apply it. Acetone is ideal for removing excess resin and for tool cleanup.
Cover exposed cabinets, floors and other surfaces before applying the resin. Wear protective eye gear, gloves and respirators for protection. Follow instructions and warnings provided by the manufacturer. You should only work in well-ventilated areas or use fans to reduce exposure to the fumes. Resins are extremely flammable; dispose of unused material or soiled rags appropriately.
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