Certain processes by virtue of the nature of the reaction interface produce zero order kinetics. Numbered among these processes is evaporation. Instances of this kind of phenomena can be cited from the cosmetic and pharmacy industries. This phenomenon can be studied using thermal analysis. However, a general model for rising temperature, solid state kinetics can be used, which is much simpler than other advocated methods. The model is based on the existence of a reaction interface and the assumption that over a small range of temperatures (say 2 degrees C) the interface area remains constant. The logical deductions from such a model are detailed in the present study.