What do we know about glass surfaces?

In many of the high-volume segments of the glass industry, it is really glass surface that is being manufactured. In some cases, the requirement for high-quality, defect-free surfaces directly limits the rate of production, while in others, it demands the extra costs of quality control inspection, the rejection of product, and/or secondary processing. This is true to varying degrees in the fiberglass, flat glass, display glass, container glass, tubing, and frit markets. For the most demanding applications, however, the ability to detect surface defects is still a fundamental limitation; this is especially true in the case of strength-controlling defects in the fiberglass and optical fibers. For other applications, the characteristics and presence of surface defects can be defined, but the origins are unknown. And in new and emerging applications of glass, for example, substrates for high-density microelectronics, storage, media, or DNA microarrays, defining and characterizing the critical nanoscale surface features still presents a great challenge. In recent years, advances in process control and quality control have led to more reliable glass surfaces and enhanced surface properties. At the same time, the availability of new analytical tools has provided the means to more directly probe the nature of glass surfaces and their behavior during manufacturing and service. The development of computer modeling and computer simulation hold promise for making theoretical predictions about surface properties and for further refinement of real-time manufacturing process control. In this review, the current understanding of manufactured glass surfaces is reviewed with an emphasis on methods for characterization and prospects for further improvement.