Does the surface has to be cleaned before using SEMCO Liquid Membrane™?

Yes! The surface of the pool shell must be clean. This step is often overlooked and can lead to problems. The first step is to remove any surface contamination left from the placement of the concrete such as form release agents, laitance (the weak, powdery cement fines which can appear on the surface of a poured, vibrated concrete wall), dust, dirt, oil, paint, concrete sealers, and curing compounds or any other material that can act as a bond inhibitor.