Primary functions of the American Society for Testing and Materials are the fostering of research on the effect of physical and chemical properties of materials upon end uses, the establishing of procedures by which significant properties can be evaluated with adequate accuracy and precision, and the fixing of limiting criteria that define the acceptability of materials for specific uses. Although these objectives are simple in principle, they usually are impossible of exact realization in practice for many reasons. For example, data and theory effecting a general correlation of a property with performance of the material in an end use frequently do not exist. Commonly, appropriate methods of testing have not been developed, or cost of labor or facilities or the required time of testing may render infeasible their application to selection and control of materials. Consequently, most methods of test that are employed for control and evaluation of technical materials are compromises in that they may not measure uniquely with accuracy the properties essential to adequate performance of the material. Rather, the practical tests commonly only generally reflect the qualities of the material, and, moreover, the test may be applicable at all only under a limited range of conditions or to only certain types of materials from among materials that can be considered to be alternatives in the selection for specific uses. In addition, the specified limits typically are established on the basis of test data that may not be generally applicable or on the basis of experience that does not cover important types or kinds of service or performance. Hence, general specifications may require modification before they can be applied appropriately to specific work.