Employee was unjamming a lightweight aggregate log in #3 cooler that was formed by an upset in the kiln. He was using an iron bar (10' long, 10lbs) to pry the log in the cooler. He was standing outside the cooler on a platform & when the log loosened/broke free, his momentum carried his left hand down onto the handrail resulting in left finger tip fracture & dissolvable stitches.