The melting stages of Chap. 3 describe the behavior of the meltwater during different time periods of the defrost process: absorption and permeation, accumulation, and draining. Meltwater accumulation reduces the strength of ice adhesion and promotes the possibility of slumping. The rate of meltwater draining depends on the boundary conditions at the interfaces of the liquid layer. A large draining rate reduces defrost time and improves defrost efficiency. Solution methods of the governing transport equations of these stages of defrost are described in this chapter.