Fabric selection for a 300-skirt school contract
A tailor in a district town has won a contract to make 300 school skirts for girls aged 14–16. The skirts will be worn five days a week for nine months, hand-washed twice weekly with bar soap, dried in direct sun, and pressed with a charcoal iron. The tailor has one industrial lockstitch machine, no overlocker, and a budget that allows 500 m of fabric. A supplier offers four fabrics at almost the same price per metre: (A) 100% cotton plain weave, 115 g/m²; (B) 67% polyester/33% cotton plain weave, 120 g/m²; (C) 100% cotton 3/1 twill, 190 g/m²; and (D) 100% polyester crepe, 100 g/m². The tailor must choose one fabric for the whole order and cannot test-wear samples. The school requires that colours match across the batch and that seams do not fray open during the school year.
1. Recommend one fabric and justify your choice using fibre, yarn and fabric-construction evidence. Explain why each of the other three is less suitable for this contract.
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Choose B, the 67/33 polyester-cotton plain weave at 120 g/m², but only if the skirt is made with flat-felled or French seams and a deep hem. The contract is dominated by repeated washing, sun drying and abrasion at the seat and hem. Polyester contributes tensile strength, abrasion resistance and colour retention; cotton contributes absorbency and comfort. A 120 g/m² plain weave is lighter than an ideal skirt fabric, so seam and hem engineering must compensate for the low mass.
A is too light and will abrade, shrink and fade; its cut edges also fray badly without an overlocker. C is durable, but 100% cotton twill at 190 g/m² will shrink and fade, is hot for daily wear, and its cut edges fray; without an overlocker, finishing every seam becomes a production risk. D is too light and thermoplastic; a charcoal iron can glaze or shrink it, and seam slippage is likely. Before purchase, ask the supplier for the same dye lot and a 30 cm × 30 cm sample of B. Wash it five times at 60°C, measure shrinkage and check colour change against the original. Reject the lot if shrinkage exceeds 2% or if the shade is visibly different from the approved sample.
2. Predict the most likely failure mode for fabric A and for fabric D during one school year, and state one objective test that would have separated them before purchase.
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Fabric A is likely to fail first at the hem and seat: the light cotton plain weave will abrade through, then fray along the seam allowances because there is no overlocker. It will also shrink and fade in sun, so hems may drop and colours may no longer match. Fabric D is likely to fail by seam slippage and iron glazing: the polyester crepe is smooth, light and thermoplastic, so seam allowances may pull apart, and a charcoal iron can leave shiny, flattened areas or shrink the fabric.
A practical pre-purchase test is a Martindale abrasion test on washed samples, using the same 60°C wash cycle. Set an acceptance criterion such as no hole after 15,000 rubs for A and B, and compare all four fabrics. A simpler workshop test is to sew a 30 cm seam in each fabric, wash it five times, and pull the seam gradually while watching for yarn slippage. For D, also press a sample with a warm iron and check for glazing. These tests separate abrasion failure from seam-slippage failure, which is the key judgement in this contract.
3. The supplier can only guarantee colour matching if all fabric comes from one dye lot. Explain how you would protect colour consistency through cutting and sewing, and what you would do if the supplier delivers two dye lots.
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Colour consistency is not only a dyeing problem; it is also a cutting and handling problem. Ask the supplier to reserve one dye lot for the full 500 m and write the lot number on the order. On delivery, check the lot number on every roll, inspect the rolls in daylight, and keep a 1 m sample from each roll as a reference. Cut all 300 skirts from the same lot where possible. If two lots arrive, do not mix them within one skirt. Sort the cut pieces into two groups by lot and keep each group separate through sewing. Assign one operator or one production run to each group, and make sure buttons, zips and thread are matched to each group. If the shade difference is visible in daylight, contact the supplier before cutting; do not rely on artificial light. If the difference is slight, use the darker lot for skirts and the lighter lot for another style, or negotiate a discount and disclose the difference to the school.