  Directional solidification occurs in industrial and natural processes, such
as freeze-casting, metal processing, biological cryopreservation and freezing
of soils. Translational temperature gradient stage allows to control the
process of directional solidification and to visualise it with optical
microscope. In this stage freezing velocity and temperature gradient are
decoupled and are independently controlled. Here we study the dynamics of the
phase transition interface in thin water samples using translational
temperature gradient stage. We follow position of the ice-water interface with
optical microscopy and compare it to solution of one dimensional Stefan problem
in the low velocity limit. We find an agreement between experimental
observations and theoretical predictions for constant velocity and during
acceleration of the ice front. This work presents a practical framework for
analysis and design of experiments on a translational temperature gradient
stage.
