Inverted cup method

Fig. 2.14 (a) Cup method (b) inverted cup method for water vapour transmission. 

ISO 15496 uses an inverted cup method for measuring the water vapour permeability of textile fabrics. A cup filled with a desiccant (e.g. potassium acetate) is sealed with a circular piece of waterproof and vapour-permeable membrane. A circular specimen of 180 mm is fitted to the groove of the specimen holder and covered by another piece of waterproof and vapour permeable membrane. The specimen holder is then inserted into the support frame, which is fitted with four vertically adjustable screws so that the specimen holder is immersed to a depth of 5 2 mm in a water bath fiUed with distilled water at 23 °C. The measuring cup is weighed at a precision of 1 mg, inverted and inserted into the specimen holder. After 15 min, the measuring cup is removed and reweighed. The water vapour transmission of the specimen is calculated by ... 

Various standard cup methods include ASTM E96 (Upright cup for water permeable fabric, and inverted desiccant and water cup methods for water impermeable fabric), BS 7208 (upright water cup method in a turning table), JIS L 1099 (Upright cup for water permeable fabric. Inverted desiccant method for water impermeable fabric (for single membrane method), and Inverted desiccant cup for water permeable or water impermeable fabric (for double membrane method)), ISO 15496 (Inverted Desiccant method for water permeable or water impermeable fabric (double membrane method)), and ISO 2528 (Desiccant method) ... 

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