Many published reports imply that Eq X1.2 is satisfactory to use for routine tear measurements. However, two serious deficiencies are evident: For many compounds there is appreciable leg extension (l fi 1) even if w is chosen to be quite wide; and secondly knotty tear is frequently encountered and the tear deviates laterally and tears through one leg of the test specimen. Development of Eq X1.1 and X1.2 is based on tear propagation down the central axis of the test piece.