Cotton Micronaire — Fineness and Maturity
topic
Micronaire (Mic) is a combined measure of cotton fibre fineness and maturity determined by airflow resistance of a 2.34g fibre plug compressed to a standard volume in an ASTM D1448 Micronaire instrument, with values typically ranging 2.5–6.5 µg/inch. Optimal micronaire for premium ring spinning is 3.5–4.9 (Upland) and 2.5–3.8 (ELS). Low micronaire (<3.5) indicates fine, immature fibre prone to nep formation and dye unlevelness; high micronaire (>5.0) indicates coarse, over-mature fibre causing fabric roughness and reduced dye uptake. Maturity ratio (MR) and fineness (millitex, mtex) can be separated using AFIS measurement: MR 0.80–0.95 and 130–180 mtex is optimal for most spinning applications. Micronaire premium band 3.7–4.2 (USDA colour grade) commands $0.02–0.04/lb price premium in cotton futures markets.
Role
Single most important cotton fibre quality parameter for spinning mill purchasing decisions, directly predicting nep tendency, dyeability, yarn evenness, and fabric hand, with micronaire-based pricing premiums and discounts determined by USDA cotton classing.