CONCRETE SURFACE RETARDERS F & S are chemical formulations which retard, but do not ?kill? the set of the mortar at the surface of concrete. When the underlying concrete has hardened, the retarded mortar surface can be flushed off with a stream of water and/or removed by scrubbing with a stiff brush. Since these compounds do not ?kill? the set, if they are left on the concrete or unintentionally splashed on other fresh concrete, they will permit the concrete to eventually attain a set and achieve full strength. These CONCRETE SURFACE RETARDERS are available in two formulations to meet varying job requirements. Formula F is a paint-like emulsion designed for application directly to forms. Formula S is a neutral, sprayable liquid for application to freshly placed horizontal concrete surfaces.