Ice segregation on a microporous filter

Ice segregation was examined on a microporous filter to elucidate the mechanism of ice segregation. The filter was a thin plastic membrane (6um thickness) with numerous micropores uniform in size. When the temperature of the air above the filter and the water under it. was lowered to slightly below 0°C, ice grew upwards from the filter. The growth rate was proportional to the degree of supercooling, being independent of the pore size. When the temperature was lowered further to a certain degree, the supercooled water under the filter began freezing, and ice on the filter stopped growing. This degree called critical temperature lowered with decreasing size of the micropores. Ice segregation was caused by supercooling of pore water, maintained by the microporous medium, and by the movement of water to the ice front.