The effect of an external electric field on the supercooling of water drops

The effect of electric fields on the supercooling of water drops was studied by a special experimental technique which permitted the observation of the action on water drops of a dc electric field of 1 to 30 kv/cm. These experiments, documented by a motion picture film, showed that freezing could be initiated in the water drops at a temperature which was only a few degrees below 0°C by applying external electric fields which had field strengths of several kilovolts per centimeter. It was found that the electrofreezing effect was not due to an orientation of water molecules in the water sample, nor was it due to participate matter produced by sparks or corona discharges since no such discharges took place during the experiments. It was found that the effect was a consequence of the movement of the drop in the electric field along a solid surface. It was concluded from the experiments (1) that an external electric field is able to activate the ice-micleability of a solid surface and (2) that the characteristics of the effect make it very unlikely that freezing can be initiated by electric fields in atmospheric clouds since the solid surfaces with which the drops have to be in contact during their deformation are not present in mature thunderstorm clouds.