4.1 All porcelain enamel coatings or glass coatings are by necessity under some degree of compression at room temperature. The desired degree of compression or stress depends upon the type of ware and the end use of the item. Some method of determining relative compressive stress of enamels is necessary to establish the suitability of an enamel for a proposed application.

1.1 This test method covers the measurement of the compressive stresses (Note 1) developed by fired porcelain enamels using the loaded-beam method.

Note 1: Although some may interpret the calculations that are used in this test method as indicating compressive load, it is commonly referred to as compressive stress within the porcelain enamel industry.

1.2 This test method is limited to the use of the loaded-beam method. However, this method includes charts (Fig. 1 and Fig. 2) that provide for conversion of loaded-beam test results to warp and ring stress values.

FIG. 2 Conversion Chart for Loaded-Beam Stress to Ring Stress

1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.

1.4 This standard does not purport to address all of the safety concerns, 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 determine the applicability of regulatory limitations prior to use.

1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.