Twist Contraction and Count Change
topic
Twist contraction is the reduction in yarn length and increase in linear density that occurs as twist is inserted, because fibres adopt a helical rather than straight path. Contraction factor = (untwisted length − twisted length) / untwisted length × 100%, typically 1–5% for cotton at normal TM. Yarn count after twisting is slightly coarser than the drafted strand count. Contraction increases with TM and decreases with fibre fineness.
Role
Twist contraction must be accounted for in yarn count calculations and delivery speed settings. Ignoring it results in off-count yarn — yarn that is systematically finer or coarser than specified — causing fabric weight deviations and customer complaints. Count correction for twist contraction is a standard calculation in ring frame setup.