TotalPond Waterfall Foam Sealant Waterfall Foam Sealant is a single-component polyurethane black foam that fills gaps and ensures efficient water flow over rocks. The foam adheres to most surfaces except: teflon, silicone, polyethylene, and other similar materials. Waterfall Foam Sealant takes approximately 5 minutes for the outer shell to dry tack-free; Compound fully cures in 12 to 24 hours. The 12 oz. can includes a nozzle tip applicator. Before using this product, make sure all surfaces the sealant will be applied to are completely dry; allow the product at least 48 hour to dry before getting it wet.