Ice growth from the vapor at -5 degrees C

The temperature was chosen because c-axis ice needles grow in a narrow temperature interval there, which coincides with the temperature at which the Hallett-Mossop ice multiplication process operates most effectively, and one may suspect that this coincidence is likely to be meaningful.

The ice growth habit is poorly reproducible in these conditions, dictating many runs with little change. Growth as plates can persist for hours, and two distinct types of needle growth occur, called sheath needles and sharp needles. Both are distinct from thin columns in that they taper to a point, with no discernible basal face.