The 100 g/m² order that weighs 58 g/m²
A weaving training centre in Nalbari has taken an order for 200 m of cotton fabric specified as "plain weave, 100 g/m², 40s count". The sample approved by the buyer was woven on a 2-shaft pit loom. On the shop floor the cloth is being produced on a 4-shaft frame loom already threaded for a 2/2 twill, and the trainee, told to "just weave plain", treadles the same two treadles as before. The cloth shows a fine, regular diagonal line on the face, and the buyer's inspection report says it "feels much lighter than the approved sample". The supervisor weighs a 10 cm × 10 cm conditioned square on a jeweller's balance: 0.58 g. The unit holds 40s cotton in stock, a 22-dent/inch reed, a 45-inch reed space, and two spare looms. The order carries a 30% advance and is due in three weeks.
1. Verify the supervisor's weight figure and calculate the sett (epi and ppi) actually needed to reach 100 g/m² with 40s cotton. State whether that sett is realistic on a handloom, and give an alternative yarn/sett plan.
Read the worked answer
Check the weight. For a cotton yarn of Ne count, metres of yarn per gram = 1.6933 × Ne. At 48 ends/inch = 1,890 ends/m, each square metre contains 1,890 m of warp:
- warp = 1,890 / (1.6933 × 40) = 1,890 / 67.7 = 27.9 g
- weft at 48 picks/inch = same = 27.9 g
- total ≈ 55.8 g/m², about 58.6 g/m² with 5% crimp.
That matches the 0.58 g per 100 cm² (58 g/m²). The cloth is roughly 42% lighter than specified.
Sett needed for 100 g/m². Each system must supply 50 g/m², i.e. 50 × 1.6933 × 40 = 3,387 m of yarn per square metre → 86 epi and 86 ppi. Cover factor per system = 86/√40 = 13.6; fabric cover ≈ 1 − (1 − 0.486)² ≈ 0.74. That is a tight, dense cloth; single 40s at 86 epi will abrade, break and weave slowly on a handloom.
Better plan. Use 2/40s (Ne 20 equivalent) at 43 epi/ppi: 50 × 1.6933 × 20 = 1,693 m → 43 ends/inch, cover factor 9.6, fabric cover ≈ 0.57. Same weight, far more weaveable.
2. Explain why the cloth shows a diagonal line, and set out the corrective action before any more metres are woven.
Read the worked answer
The diagonal is not a yarn or finishing fault - it is the weave. The loom is threaded and tied for a 2/2 twill, so whichever two treadles the trainee presses, the shedding program still lifts shafts in a 2-and-2 sequence. Each warp end floats over two picks and under two, and the offset between neighbouring ends produces the continuous diagonal ridge that reflects light as a line. A single bent reed wire or trapped end would give one straight, localised mark, not a full-width diagonal repeating every four picks - so the repeat interval itself is the diagnostic clue.
Corrective action:
- Re-thread the healds in plain order (1, 2, 1, 2 …) across the full width, or use shafts 3 and 4 if the twill draft must be kept for another order.
- Re-tie the treadles so each treadle lifts only one shaft, giving the 1/1 alternation.
- Weave 20 cm and confirm with a pick glass that every pick crosses alternately over and under.
- Record the draft alongside the order so the same error cannot recur.
If the buyer actually wants a twill, the specification and price must be renegotiated - but this order is plain weave.
3. Give a production plan that meets the three-week delivery: yarn, sett, reed and loom capacity.
Read the worked answer
Yarn and sett. Switch to 2/40s at 43 epi/ppi (see weight calculation): 43 × 45 inches = 1,935 ends; round to 1,936 so the count divides by 4 for selvedges. Selvedge: 4 ends per dent for 8 dents each side; body: 2 ends per dent in the 22-dent/inch reed gives 44 epi - adjust cloth width slightly or use a 21½-dent reed to land on 43.
Capacity check. Picks per metre = 43 × 39.37 = 1,693; for 200 m = 338,600 picks. At 30 picks/min on a handloom: 11,287 min ≈ 188 weaving hours ≈ 23.5 eight-hour loom-days. Add 25% for gaiting, repairs and weaver breaks → about 29 loom-days.
Plan. One loom cannot deliver 29 loom-days in three weeks (≈18 working days). Run the order on two looms in parallel, each weaving 100 m (≈15 loom-days each), which fits the deadline with a small buffer. Warp beam 1 is gaiting while beam 2 is woven. Book the two spare looms now, prepare both warps in week 1, and inspect the first 10 m against the approved sample before committing the balance.