Abstract: A method for the surface treatment of a substrate, for example concrete roof tiles, comprising spreading a layer of water-containing hardenable paste containing binder and other particles, for example a cement based slurry, covering the paste layer with (a) a flexible membrane or (b) a plate or (c) first a flexible membrane then superimposed thereon a plate, the plate or membrane having an upper-surface and a smooth under-surface, optionally vibrating the membrane-covered or plate-covered area of the paste layer, such that vibration is transmitted through the membrane or plate, to the paste layer, and either removing the membrane, plate or plate and membrane then hardening the paste layer on the substrate, or at least partially hardening the paste layer on the substrate with the membrane, plate or plate and membrane in place.