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queous film-coating processes can influence many quality aspects of the final coated product, including coated-tablet moisture content, surface roughness, gloss, coating efficiency, and coating uniformity. Colorcon’s aqueous tablet-coating formulations must be capable of meeting these and other customer requirements in different application environments around the world using various types of coating process equipment. Many different tablet coating machines are on the market, each with different configuration options and different controllable process parameters. Further, different configuration options can be non-numeric. For example, some machines can be configured with one or more spray guns. This situation can result in discontinuous effects on coatedproduct quality and performance. One critical consequence is that it is not possible to define one process operating specification that is optimal for all coating conditions. The wide range of coating conditions (operating parameters, equipment, and configuration options) also has a profound consequence in terms of the development of robust coating formulations. Such a robust formulation is one that is insensitive to “normal” coating process variation. The first level of normal variation is the operating tolerances of the controllable process parameters. However, normal variation should be extended to include the likely range of uncontrollable environmental factors known to affect product Stuart C. Porter, PhD, is vice-president, and Charles R. Cunningham is global technical manager, excipients, both in Global Technology Development at Colorcon, 415 Moyer Boulevard, West Point, PA 19486, tel. (215) 661-2517, fax (215) 661-2505, email ([email protected]). Richard P. Verseput is president of S-Matrix Corporation in Cupertino, CA.