Before nucleation, no ice is present and the enthalpy balance simplifies accordingly. Importantly, the time at which nucleation occurs vary among vials. After nucleation, the enthalpy balance governs the evolution of both temperature and ice mass, together with eqn. 5, the constitutive equation for the equilibrium freezing temperature. As outlined in section 2.1.1, the enthalpy balance for the this phase is subject to the following initial condition: