Yarns and Fabrics
Yarns and Fabrics
This domain examines yarn numbering, twist, fabric formation, fabric weight and basic performance. Expect count conversions, woven vs knitted structure and fault tracing.
Core rules and concepts
- Yarn count expresses linear density or fineness. In cotton count (Ne), higher number means finer yarn; 1 Ne = 840 yd per lb. Tex is grams per 1,000 m; higher tex is coarser. Denier is grams per 9,000 m.
- Twist direction is S or Z; twist level affects strength, handle and hairiness. Plied yarns are named by ply and count, for example 2/60s Ne.
- Woven fabric has warp and weft; knitted fabric has wales and courses. Woven structures include plain, twill and satin. Knitted structures include single jersey, rib and interlock.
- Fabric weight is usually grams per square metre (GSM). It depends on yarn count, cover, crimp and finish.
- Grain, skew, bow and shrinkage affect garment fit and must be checked before cutting.
Worked example
A roll is 100 m long, 1.50 m wide and 150 GSM. Area = 100 × 1.50 = 150 m². Mass = 150 m² × 150 g/m² = 22,500 g = 22.5 kg. If the same fabric were 180 GSM, the mass would be 27 kg, because mass scales directly with GSM at constant area. For costing, add wastage and shrinkage only after calculating the base fabric mass.
Traps
Do not compare Ne and tex numerically; convert first. Do not confuse wales with warp ends. Do not use fabric width without checking usable width after selvedge trimming. Do not treat GSM as a count.