  The formation mechanism of ice banding in the system of freezing colloidal
suspensions, which is of significance in frost heaving, ice-templating porous
materials and biological materials, still remains a mystery. Recently, the
theory of secondary nucleation and growth of ice has been proposed to explain
the emergence of a new ice lens. However, this theory has not been
quantitatively examined. Here, we quantitatively measured the initial
interfacial undercooling of a new ice lens and the nucleation undercoolings of
suspensions. We found that the interfacial undercooling can not satisfy the
nucleation undercooling of ice and hence disprove the secondary nucleation
mechanism for ice banding.
