“…[10][11][12][13][14][15] The apparent viscosity may increase significantly by liquid-liquid separation, nucleation or/and crystal growth phenomena, 5,16 reaching values 10 4 -10 6 times higher than the shear viscosity of the parent melts. An example is the glass-ceramics production cycle, where the rise of the heating rate between the nucleation and crystallization steps depends on the increasing of the apparent viscosity: at low heating rate, due to the formation of a crystal phase, the apparent viscosity increases thus avoiding the deformation of the products; at a high heating rate the glass-ceramic may be deformed under its own weight.…”