The sealant installed must perform a number of very important function: keep water and fines from infiltrating the joint; prevent larger incompressible materials from penetrating the joint space and staying there; and perform satisfactorily over a long span of time. The American Society for Testing and Materials (ASTM), recognizing that the old specifications issued in 1952 need upgrading, has prepared "Tentative Specification for Joint Sealants." This specification includes a resiliency requirement as a measure of ability to reject incompressible, allows no flow at 158 degrees F and has an artificial weathering test requirement to indicate life expectancy. Several manufacturers produce polyvinyl chloride-coal tar sealants to meet the requirements of this specification. These sealants, even after extended exposure to the extreme conditions of this test, will not flow, exhibit tackiness, show the presence of an oil-like film or reversion to a mastic-like substance, form surface blisters or internal voids, undergo surface crazing or cracking, suffer hardening, or lose resilience or rubber-like properties. Evidence of physical change in the surface of the material by visual and tactile examination constitutes failure of the material under this new specification. Care must be taken to keep the sealant below the surface of the pavement so that in hot weather it will not be extruded up out of the joint where wheel traffic can hit it and break the bond of the sealant to the sidewalls. If this bond is broken and the upper portion of the sealant is pulled away from the joint face, fines and sand can work down into this opening and cause failure of the sealant. Proper joint cleaning is of equal importance to material selection, joint shape and sealant installation. Sand-blasting or high-pressure jet water cleaning is mandatory to remove dust or paste left from sawing. In some cases this material must actually be plowed out following sawing and prior to sandblasting or waterblasting.