twisting due to the increasing tension and pressure of the bundle of fibres in the yarn. It may become so strong that the thread core buckles when it can no longer withstand the compressive strains. The yarn curls, meaning that the yarn tries to reach a state of equilibrium in which twists in the opposite direction from the original twist direction balance the yarn's torque. These twists are also called negative twists. In this state of equilibrium, the inner torsional tensions cancel each other out. The thread always buckles at a spot where the cross section is small due to the unevenness of the thread. During the spinning process this spot took up more twists and is therefore subjected to higher inner tensions, which ultimately break the thread core. Although thicker yarns are less twisted than fine ones, the inner tension rises opposite to the yarn size. Smaller yarn is more weakened by steaming. Further positive aspects of steaming are the reduction of curling and, at the same time, the setting of the physical properties of closeness and extension imparted to the yarn by twisting.