HEF Black Underlayment is a low viscosity, 100% solids, solventless, two part epoxy. It is designed to enhance the appearance of the floor substrate. HEF Black Underlayment can be used as a primer, a concrete repair mortar, a broadcast, a resurfacing screed or a self-leveling slurry system. HEF Underlayment is NOT to be used as a topcoat.