A steel strip (10) is conveyed through a galvanizing bath (20) of molten zinc, a zinc coating weight control device (12), and a minispangle box assembly (16). The steel strip emerges from the zinc coating weight control device (12) with a non-uniform temperature distribution across its width in which it is warmer in the center and cooler at its edges. A differential, pre-cooler assembly (18) cools the steel strip selectively and non-uniformly across its width in a manner which is complimentary to the temperature distribution thereacross. In this manner, the steel strip exits the pre-cooler assembly (18) and enters the minispangle box assembly (16) with a more uniform temperature distribution. This results in a more uniform minispangle appearance on the strip (10) as it exits the minispangle box assembly (16). The pre-cooler assembly includes a plurality of nozzle pairs (32a, 32b; 34a, 34b; 36a, 36b; 38a, 38b). The nozzles of each nozzle pair are disposed in a facing relationship on opposite sides of a work path, and include a pair of conduits (60a, 60b) which define an array of apertures (62a, 62b) therealong. A damper (66a, 66b) is provided to selectively cover the apertures in each array. Each damper has a leading edge (72a, 72b) which is somewhat U-shaped so that as the damper is adjusted relative to the associated conduit, the apertures of the array are progressively covered from the outer edges toward the center, or progressively uncovered from the center toward the edges.
