oil was placed on the sample the time required for the film to completely change color was measured by an observer using a stopwatch and is reported in table 1 in seconds a microporous film was prepared similar to that described in pct application wo99 29220 example 1 having the following composition polypropylene 71 6 union carbide co 5d45 mineral oil 28 white oil 31 amoco oil and chemical co red iron oxide pigment concentrate 0 3 americhem nucleating agent 0 04 millad 3988 milliken the microporous film had a thickness of approximately 38 microns a microporous film was prepared similar to that described in pct application wo99 29220 example 1 having the following composition polypropylene 63 75 union carbide co 5d45 mineral oil 35 white oil 31 amoco oil and chemical co red iron oxide pigment concentrate 0 3 americhem nucleating agent 0 95 millad 3988 milliken the microporous film had a thickness of approximately 38 microns a microporous film was prepared similar to that described in pct application wo99 29220 example 1 having the following composition polypropylene 53 6 union carbide co 5d45 mineral oil 45 white oil 31 amoco oil and chemical co red iron oxide pigment concentrate 0 3 americhem nucleating agent 1 15 millad 3988 milliken the microporous film had a thickness of approximately 38 microns a microporous film was prepared similar to that described in example 1 having the following composition polypropylene 53 union carbide co 5d45 mineral oil 42 white oil 31 amoco oil and chemical co and phthalo blue pigment nucleator concentrate 5 ppn 71512 80 20 polypropylene pigment tokyo printing ink corp the microporous film had a thickness.