 In Hungary, the steel cylinder or roller mill, locally known as the "Walzenmühle", was first invented, and later improved.The Walz sets kept the grain cooler over multiple passes, as successive pairs of rollers were adjusted to incrementally smaller spacings, the grain moved through cooling air from one pair to the next, each cracked them pass-by-pass into smaller successive bits, instead of crushed between stones in one heat-generating pass.At the Pesth Walzenmühle, when wheat had been fully transformed to flour, it had passed through 18 to 24 pairs of rollers.