West System® 422 Barrier Coat Additive. Designed to improve cured epoxy's moisture exclusion effectiveness. Can be used as a barrier coating additive to help prevent gelcoat blistering in polyester fiberglass boats. Increases the epoxy's abrasion resistance. Designed for moisture resistance, abrasion resistance and preventing gelcoat blistering. Can be blended into any West System® 105 Epoxy Resin®/200 Series Hardener combination. Mix ratio is 15% - 20% by volume (One 16oz can will modify up to 0.5 gallons of mixed epoxy). Cures to a light gray color. Light Gray. 16 oz.