During steaming, the heating of the fiber causes its molecules to start oscillating. The increase of oscillation that can be influenced by the degree and the period of heating dissolves the electric bond forces in the fiber; at first in the amorphous domains, later in the crystalline ones and at last in the polymers. As with wool, the tensions brought in by spinning are set free. During drying or cooling of the fiber, the binding forces are rebuilt without having tensions in the inner part.