1.1 This test method covers four procedures for determining the machine direction of most grades of paper and paperboard, embodying the principle that machine direction alignment of fibers results in:
1.1.1 Cross-direction shrinkage to produce curl with axis in machine direction,
1.1.2 Higher cross-direction tear,
1.1.3 Higher tensile strength in machine direction, and
1.1.4 Higher stiffness in machine direction.
1.2 Application of the procedures in this method to certain grades of paper, such as sheets laminated to film, creped papers, extensible papers (where it is not unusual for the machine direction tensile to be relatively low and the stretch to be relatively high) and papers reinforced with textile materials, may result in unreliable determinations.
1.3 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 and health practices and determine the applicability of regulatory limitations prior to use.