The first of these factors is known as ballooning. As the yarm is unwound from the package at high speed, centrifugal force causes it to ollow a curvedpath. Asthe yarn rotates, it gives the illsion of a balloon above the package. This alloon-ingleads to uneven tensions being produced in the yarn which may or may not altersome of the particular properties of the yarn. The second factor for consideration is that for each time one complete wrap of yarn is removed from the supply package, the twist in that length changes by one turn. For most yarns this change is insignificant and may be ignored. However, some fabrics areconstructed using flat yarns of metal, polymers or rubber. In these cases the yarn mustremain flat and even one turn of twist is unacceptable. These yams cannot be unwoundusing the over-end method and the side method must be used.