CND SHELLAC Top Coat. A single layer provides the durable mirror-like finish. CND SHELLAC was designed to be used as a system. Featuring a Base Coat, Color Coat, and Top Coat together with the exclusive CND SHELLAC Lamp – CND delivers on its promise of two week wear, when used as a complete nail system. CND SHELLAC Color Coat applies in two coats for rich, lush color that lasts two weeks.