Previous studies of s-weakening in Spanish have relied almost exclusively on the impressionistic coding of /s/. Not only is auditory transcription invariably influenced by the transcriber’s background, but temporal and gradient acoustic details about the sound are concealed when tokens are represented symbolically. The present study examines the production of /s/ by eight females from Cali, Colombia during informal sociolinguistic interviews. We propose a metric for quantifying s-realization by employing three scalar dependent variables: s-duration, centroid, and voicelessness. The results of linear regressions indicate that the dependent variables are significantly conditioned by local speaking rate, lexical frequency, stress, word position, and the preceding and following phonological contexts. This study sheds light on how each independent variable impacts s-realization acoustically. For example, as local speaking rate increases, duration, centroid, and voicelessness decrease, indicative of lenition. We discuss the advantages of opting for instrumental measurements over symbolic representation.