The specific irreversibility of solidification and of cyclic solidification-melting process was considered on a general level. The variables affecting the irreversibility most are the Biot number, the dimensionless interfacial speed during recalescense and the extent of supercooling. The process path involving supercooling can become less irreversible than the path where phase transition completely happens in an equilibrium state if a thermal conductivity ratio between solid and liquid phases is sufficiently below unity. A finite maximum and a non-zero minimum value of irreversibility can be detected. These extreme values are independent of the geometrical shape of the substance. (C) 2011 Elsevier Ltd. All rights reserved.