Meaning and Purpose
4.1 The roundness of a glass sphere is a measurable aspect related to its performance as a retroreflective medium. The function of this test method is to measure the percentage of true spheres associated with compliance with the applicable specification.

Note 1: This method has been used in other industrial areas beyond the intended scope of this test method.

ASTM D 1155-2020 “Angle of Glass Beads”

Scope of
1.1 This test method 2 covers the determination of the percentage of true spheres in glass spheroids used for reflective marking purposes and for industrial use.

1.2 The test method includes the following two processes:

1.2.1 Procedure A, where the selected specimens are divided into two size ranges or groups and then separated into true spheres and irregular particles, and

1.2.2 Procedure B, where the selected specimens were divided into five size ranges or groups prior to separation.

1.2.3 In determining compliance with the requirements of the code, procedure A or Procedure B may be used. If the test indicates failure to reach the specified percentage of true spheres and irregular particles, a referee test shall be performed according to procedure B.

ASTM D 1155-2020 “Angle of Glass Beads”

1.3 Values expressed in SI units shall be regarded as standards. The values given in parentheses are for reference only.

1.4 This standard is not intended to address all safety issues, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health and environmental practices and to determine the applicability of regulatory restrictions prior to use.

1.5 This international Standard has been developed in accordance with the internationally recognized standardization principles established in the Decision on Principles for the Development of International Standards, Guidelines and Recommendations issued by the Committee on Technical Barriers to Trade of the World Trade Organization.