D2941-21 – Standard Test Method Technical Guide

ASTM D2941-21, officially titled the Standard Test Method for Measuring Break Pattern of Leather (Break Scale), provides a robust framework for evaluating the surface wrinkling behavior of shoe upper leather using a visual reference scale. Developed under the jurisdiction of ASTM Subcommittee D31.03 on Footwear in cooperation with the American Leather Chemists Association, this method is crucial for determining the aesthetic and structural quality of cut parts intended for footwear. This test method does not apply to wet blue or wet white leather.

📐 Scope, Terminology, and Specimens

The scope of D2941-21 specifically covers the measurement of the break pattern in shoe upper leather. The “break” of leather is formally defined in the standard as “the pattern of wrinkles formed on the grain surface of upper leather when it is bent grain in to form a concave surface.” This directly simulates the bending condition of the leather in the vamp of a shoe during walking. Test specimens must be taken from an agreed area of the hide and measure exactly 2 in. × 4 in. (50.8 mm × 101.6 mm). All values in the standard are stated in inch-pound units, which are to be regarded as standard.

⚙️ Significance and Core Apparatus

The break pattern is highly dependent on the fiber structure and the cohesion between the grain and the corium. A fine break reflects favorably upon appearance and serviceability, while a coarse break may indicate the grain layer is separating from the main stratum (pipey leather). The primary apparatus includes the Satra Mandrel, consisting of two windows or hollows, and the Satra Visual Break Scale, which provides eight distinct levels of break ranging from Level 1 (fine) to Level 8 (coarse).

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