Retarded surface finish
Retarding the surface concrete produces an effect similar to acid etching (see separate entry Acid etched finish). There are three main methods of retarding the surface: a retarding agent is painted on to the formwork, retarder paper is laid against the formwork or a surface retarder is applied to the unformed concrete surface after casting. In all cases the retarder prevents the surface of the concrete from hardening and allows it to be removed by either high-pressure washing with water or by brushing. Using different strengths of proprietary products controls the depth of retardation and the subsequent depth of texturing.
WARNING: The various surface retarding methods must be used strictly in accordance with the appropriate COSHH Regulations and in accordance with the manufacturer’s recommendations.