Textile Testing and Quality Control
What the exam tests
You must know which test measures which property, the standard conditions, and how to interpret a result against a specification. Numerical questions on count, GSM, CSP and shrinkage are common.
Standards and conditioning
Testing follows IS (BIS), ISO or ASTM methods, and the method number should be quoted in a report. Samples are conditioned before testing because moisture changes mass and strength; the standard atmosphere is 65 ± 2% relative humidity, and Indian practice often uses 27 ± 2 °C with that humidity.
Core tests
- Yarn: count, twist, lea strength and CSP, evenness, hairiness, imperfections.
- Fabric: GSM, thickness, ends and picks, tensile strength (strip or grab), tear strength (Elmendorf), bursting, abrasion (Martindale), pilling, crease recovery, stiffness, air permeability.
- Colour: fastness to washing, rubbing (dry and wet), light, perspiration and water; ratings use the grey scale (1–5) and, for light, the blue wool scale (1–8).
- Others: dimensional stability after washing, pH of aqueous extract, formaldehyde.
Worked example
A 40s Ne cotton yarn gives a lea strength of 70 lb. CSP = lea strength × count = 70 × 40 = 2800. If the buyer's specification is a minimum of 2600, the lot passes. Had the count been 30s with the same lea strength, CSP would be 2100 and the lot would fail - showing why CSP compares yarns of different counts fairly.
Traps that cost marks
CSP is not the same as single-thread strength. Wet strength differs from dry, especially for viscose and cotton. A higher fastness number means better fastness. Rubbing fastness is usually lower when wet. Always state the test method and conditioning, because results are not comparable across methods.