Experiments on solidification of aqueous solutions are sometimes carried out in tanks with transparent sidewalls to allow visualization of the flow and crystal structure. The tank sidewalls must be thermally insulated and condensation of water vapor on the outer sidewalls must be prevented for clear visualization. In this note a system is presented which is capable of eliminating the water vapor condensation, providing thermal insulation and thus facilitating continuous flow visualization of the solidification process. Some visualization photographs are presented.