Methods for understanding the fundamental mechanisms of laser photothermal imaging are described and applied to model imaging media. The light response is characterized with a series of Gaussian laser pulses of varying intensities and durations. The results are compared to a reference model, the "local fluence" model, that assumes the likelihood of exposure at a given pulse duration depends solely on the laser fluence received at that location. The mechanisms underlying the material behavior are studied with time-resolved microscopy using a variety of exposure and viewing conditions. The imaging media have in common a silicone rubber (polydimethylsiloxane) coating that can be removed by a single laser pulse to form an imaged spot that attracts ink. They differ in having a thin-film absorber layer, a volume absorber layer, or a combination of volume absorber and energetic underlayer. The thin-film media are the least sensitive with longer duration microsecond pulses but the most sensitive with nanosecond pulses, which is explained using a thermal conduction model. The volume absorbing media show deviations from the local fluence model that indicate the existence of useful dot gain properties which improve sensitivity. Time-resolved microscopy shows that this dot gain results from high-speed mechanical effects caused by hot gas trapped under a silicone rubber balloon.