422 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Figure 6. Apparatus for performing tearing tests on fingernails methods to use as a guide, and we were forced to develop our own criteria for sample evaluation. Before beginning the test, each fingernail specimen was carefully measured. The sam- ples were then subjected to stress until failure occurred, and the force necessary was recorded. The results were plotted as tearing resistance in pounds per inch of nail thickness. A total of 15 fingernail samples were tested, and the values obtained ranged from 274.3 to 676.2 lb/in. IMPACT ABSORPTION TESTER The objective of the impact absorption test is to determine the effect of the impact of a swinging pendulum on a rigidly clamped sample. As with the previous tests, we found

MEASUREMENTS ON FINGERNAILS ... Figure 7. Apparatus for performing impact absorption experiments 423 that there was no suitable equipment available for testing samples of this size. Unlike the previous tests, however, this experiment could not be performed in the Instron or by modifying any other existing equipment. The simple apparatus which we have developed for this purpose is shown in Fig. 7.