In this investigation into high temperature plasticity, sodium nitrate has been used as an analogue material to study microstructural changes during deformation, particularly dynamic recrystallization. The occurrance of dynamic recrystallization during creep and hot working of metals is well established, but more recently advances in geology have led to the recognition that dynamic recrystallization has played an important role in the microstructural development of many rocks. Although there have been many systematic studies of dynamic recrystallization, there is no clear evidence of how nucleation occurs. Due to the difficulty of inferring mechanisms from resulting microstructures, a technique was developed which enabled, via the optical microscope, the continuous observation of the microstructure as it evolved during high temperature plastic deformation.