Exposed concrete surfaces in a multitude of shapes and textures have been most acceptable architectural media for many years. Currently, a popular architectural expression is the use of white concrete with the surface removed to expose the aggregate. Such surfaces, however, may be susceptible to discoloration by atmospheric contaminants in highly industrial areas because (1) the white color shows color changes more readily, (2) the rough textured surface tend to trap dirt particles, and (3) the surface of the matrix may be susceptible to penetration by products that cause discoloration. Many architects, recognizing this problem, are specifying that such surfaces be protected by application of a water repellent coating. Ideally such coating materials should be water-clear, be capable of being absorbed into the concrete surface, be long lasting, not impart a glossy coating effect, and not discolor. A great number of products, of varied chemical composition, are sold for this use. We conducted a study to determine the effectiveness of a variety of such coating materials. The spectroscopic analyses indicated many of the coatings to be a mixture of at least two materials that could be identified; in some cases very minor constituents, thought to be plasticizer, could not be identified. The compositions of these coatings, as determined by spectroscopic analysis are listed in charts found in the article. These tables list the coating in order of their performance on exposed-aggregate and smooth surfaces, respectively. Where more than one constituent was found the major one was listed first. Among coaters which were found to be excellent were: a ethyl acrylate polymer, a polyester-epoxy resin, a methyl methacrylate and ethyl acrylate copolymer, a styrene-acrylic copolymer, and a styrene-acrylic-silicone terpolymer.