THEORY OF THE BEHAVIOR OF GLASSWARE IN SERVICE*

Abstract

The most important characteristic of a piece of glassware such as a bottle or a jar is its serviceability, that is, the amount of use which can be obtained from it. In the case of glassware which is subject to repeated re-use, this serviceability may be thought of in terms of length of life, measured either by months or years, if the service is uniform, or measured by the number of trips successfully undergone if it is not. The termination of the serviceability of such glassware is due to breakage, and breakage in turn is, in the vast majority of cases, due to impact. But a piece of glassware may survive many severe impacts, only to succumb to a comparatively minor one. Impact alone is not the whole story. Glassware must be prepared for breakage by undergoing a process of use and abuse during which the surface is scratched, abraded, and otherwise damaged and thus rendered vulnerable to the final stroke. In the present paper the assumption is made that in nearly all cases breakage involves two separate and independent processes, the “vulnerating” process and the final impact. On this assumption a mathematical treatment is evolved which yields a mortality curve showing the relation between the rate of breakage and the service age of a given installation of glassware. This curve has been found to represent quite accurately the results of a service test on glass tumblers conducted in an actual restaurant. Impact strength, as determined by laboratory tests, declines with service age in a way consistent with the above assumption. These strength data, furthermore, may be correlated with the results of the service test. Additional data are being secured from other service tests now in progress.