An economically fabricated trigger for initiating crystallization of supercooled solutions in flexible plastic containers (11). The trigger comprising a thin substantially imperforate metallic strip (14) having a perimeter bounding a generally dish-shaped (30) or concave portion. The strip (14) further having a plurality of spaced, generally V-shaped elongated grooves (15-22) formed inwardly from the perimeter. The strip having two configurations between which it is distortable or bendable with snap-displacement causing the initiation of progressive exothermic crystallization of said salt in the solution (12). The scrip metal being typically impacted during fabrication to impact orient the molecular structure so as to aid the functioning of the disc or strip to produce or initiate crystallization.
