The ring and ball method of test for softening point of bituminous materials, resins, and similar substances

Abstract

The softening point of materials which, like asphalt, have no definite melting point, but which when heated gradually change from brittle or very thick and slow-flowing materials to more mobile liquids, can only be determined by some arbitrary method. The ring and ball method which briefly consists of determining the temperature at which a disk of the material held in a ring and loaded with a ball will flow through a definite distance when heated at a prescribed rate is one of the best methods for such tests. Published directions for making the test are, however, open to very serious objections, and this paper describes the apparatus and procedure used at the National Bureau of Standards. The principal modifications in the apparatus are a beveled instead of a cylindrical ring, and a centering device for the ball.