Large, completely smooth concrete surfaces of a uniform color have long been an ideal of architects. For one reason, considerable savings are possible when the outside of the structural concrete requires no plastering or cladding. The designer's ideal can seldom if ever be realized in actual practice because the difficulties on site can be formidable. Sooner or later even initially successful results may have to be hidden by cladding or at least a coat of paint. This was a practical reason for introducing the practice of treating concrete surfaces to make then unintentionally uneven and therefore minimize the effect of construction blemishes. Textured concrete surfaces, changing their appearance in the play of sunlight under different angles from morning to noon and from season to season, have given new scope to architectural treatment. A number of means have been developed for producing them. Rough sawn timber board- this is still the lowest priced route to form making. Such boards can be used repeatedly, but with those repeated uses they will normally show different concrete textures as time goes on. Different degrees of humidity in the wood boards, variations of temperature, the effect of the ultraviolet rays of the use, as well as varying amounts of resins in the wood tend to make this method unfeasible when high quality is required. Expanded polystyrene- this type of form liner first become known in Switzerland, where it soon found many users because naked concrete surfaces had never been popular there. These expanded polystyrene panels with various textures are one shot items. Usually, they are left on the finished concrete wall after stripping to protect it from damage and are removed only in the final stage. Liner matts of synthetic rubber can be made to large widths and lengths, much like the material used floor coverings. These mats are up to about one-half inch thick and the depth of the embossed design is usually on the order of one-tenth to one-fifth inch. Polyethylene and polyvinyl chloride film in thickness of one-fiftieth to one-tenth of an inch are made with surfaces structured by embossing, hot pressing or deep drawing by vacuum. Their surfaces are so smooth that in some cases no release agents are needed to recover them for the formed concrete surface.