System Three Coating Epoxies offer tremendous benefits in protecting and stabilizing wood components. Not only do they offer exceptional protection from moisture, but they also bring out a high degree of depth and beauty to wood. Coating epoxies can be used as the sole finish, or they can be implemented as a high-build protective sealer. Most waterborne or solvent-based topcoats can be applied over System Three Epoxies. Exterior applications require a UV protective topcoat such as System Three Marine Spar Varnish or System Three WR-LPU. Always test if not using a System Three topcoat.
Stain can be used with System Three Coating Epoxies. However, extended dry time of the stain is necessary before coating can begin. Traditional oil based stains work best but need 5-7 days at room temperature to fully dry. Waterborne and gel stains are not recommended. As always, test your stain color with the epoxy before proceeding to your project.
Wood must be clean and verifiably dry before coating can begin. High moisture content can be problematic and should be avoided until moisture levels drop to 12% or less.
Sharp edges and outside corners are difficult to coat and more times than not, inadequate film build occurs, resulting in poor protection from moisture. To prevent potential failure of the epoxy, edges and outside corners should be slightly rounded over. You can round over or break the edge with sandpaper or using a router and a small radius round-over bit. Sand with 180-220 grit sandpaper. Remove sanding dust from the wood substrate with clean shop air, or a vacuum.
Measuring and Mixing:
Most System Three Epoxies are mixed at an easy 2 Parts Resin to 1 Part Hardener. Once epoxies are mixed, they have a limited pot life. Because of this, it’s best to start with small 3 - 6 ounce batches to prevent loss of material. In a disposable graduated cup pour in 2 Parts Resin and then follow by adding 1 Part Hardener. Mix with a flat stir stick, by scraping the sides, stirring from the bottom up. Pour contents into a paint tray or disposable pie tin. Spreading out the epoxy prevents heat buildup and therefore increases your pot life.
For interior applications, apply at least 2 coats of epoxy. Exterior applications require 3 or more coats for good outdoor durability.
System Three Coating Epoxies are best applied with a 1/8” nap foam roller and disposable natural bristle brush. Use the natural bristle brush to reach areas the roller cannot. Optimal results are attained when the wood substrate is sealed with a very thin layer of System Three Epoxy at ½ fluid ounce per sq. ft. Some porous woods may need an additional thin seal coat, applied at ½ fluid ounce per sq. ft. Once the wood is sealed, additional coats can be applied. Aim for 1-2 fluid ounces per sq. ft. Vertical surfaces require thin coats to prevent runs or sags.
Note: Sanding between coats is generally not advised. The sanding dust produced is very persistent and difficult to remove from porous grain. If not completely removed, fine white specks will show on the next coat. If sanding is necessary, use 150-grit sandpaper. Fine sanding dust can be removed with careful use of clean shop air or a good quality vacuum. Wipe the surface with denatured alcohol.
Unlike other finishes, you can apply System Three Epoxy over itself, even when the prior coat is still tacky. System Three Epoxies have a 72-hour window during which sanding is not necessary between coats.
When the epoxy has cured to a sandable state (24-36 hours) most topcoats can be applied. Some spar varnishes are not compatible with epoxy. Be sure to test ahead of time to determine compatibility.
Sand the System Three Epoxy with the finest grit that efficiently levels the surface. We have found that 150-180 grit is a great starting point. Best results are achieved by using a hard-backed sanding block or electric sander with a dense rubber pad. Care should be taken when using electric sanders, as too much of the epoxy surface can be removed.
When sanding, be sure to maintain the proper grit sequence. Failure to maintain grit sequence can end in scratches showing through the topcoat. Finishing with 320-grit sandpaper is recommended for gloss finishes. Satin finishes can be sanded up to 220-grit.
An exterior application will need at least three coats of a UV protective topcoat for prolonged durability. UV protective topcoats will periodically need recoating. When the UV protective coating begins losing it luster, you should plan on recoating soon.
For more information, see our detailed literature on coating and finishing outdoor wood.