Diffraction rings due to spatial self-phase modulation of a continuous wave, visible laser beam were observed in a photopolymerizable organosiloxane medium. Self-phase modulation originates from laser initiated free-radical polymerization and corresponding changes in the refractive index of the medium. This study focuses on the differences in the photoresponse of the organosiloxane relative to other nonlinear optical materials and the opportunities that they provide to probe previously inaccessible properties of the self-induced diffraction rings. Specifically, the noninstantaneous response of the organosiloxane enabled diffraction rings to propagate through long distances ( length) in the medium without disruption from optical self-focusing. It was moreover possible to monitor the temporal evolution of the rings, and thereby gain direct insight into the dynamics of self-phase modulation. Furthermore, changes in refractive index due to polymerization were permanent and provided a direct view of the conical trajectory of the diffraction rings through the medium.