Even though concrete itself offers a broad range of attractive surface appearances (plain, exposed aggregate, integrally colored, specially formed, bushhammered, acid-etching, to mention just a few) there will always be some demand for concrete that doesn't look like concrete. The need for compatibility with certain architectural styles and personal preferences is a major factor; users often want the durability and versatility of concrete along with the appearance of such traditional materials as brick, stone, tile, and cobblestones. A process developed many years ago in California but just recently perfected and patented, now allows the builder to combine the appearance of these older materials with the advantages of concrete slab construction. The process, called pattern stamping, involves the use of patented aluminum tools to imprint patterns on freshly placed horizontal concrete surfaces such as floors, patios, driveways, walkways, and pool edgings. With the pattern imprinting process, the pattern is achieved by placing a special tool on the surface of the concrete while it is still in its plastic state and tamping the tool into the surface. Various tools have blades in the configurations of brick tile, cobblestone and other patterns. Although pattern stamping is basically a simple process, a few rules should be observed to assure uniform, acceptable surfaces. The mix should incorporate coarse aggregate no larger than one-fourth of an inch. The concrete should have sufficient fines and gradation of aggregates to produce a workable, finishable material. This often means that the cement content will have to be increased somewhat over that of a mix with the same top size aggregate designed for other uses. Since most pattern stamped surfaces will be exposed to wetting-drying and/or freezing-thawing, the concrete should be air-entrained. If the air content is held within limits to avoid stickiness, air entrainment will facilitate the stamping and finishing steps.