BS ISO 22958:2021 pdf download – Textiles — Water resistance — Rain tests: exposure to a horizontal water spray.
8 Procedure 8.1 The test specimen, backed by a (150 mm ± 3 mm) × (150 mm ± 3 mm) piece of textile blotting paper weighed to the nearest 0,1 g, is clamped in the specimen holder and the assembly is mounted in a vertical, rigid support frame positioned to locate the specimen in the central portion of the spray at a distance of 305 mm from the face of the spray nozzle. 8.2 A horizontal water spray is directed against the specimen and is allowed to continue for a period of 5 min at the specified pressure head. NOTE Most of the time, a specified pressure head is given when this test is requested. However, as stated in 9.2, different pressure heads can be used to obtain a complete overall picture of the penetration resistance of a fabric. If no pressure head is specified, use 600 mm for initial testing. 8.3 At the end of the spray period, the blotter is carefully removed and quickly reweighed to the nearest 0,1 g. 8.4 The number of test specimens required will be governed largely by the degree of accuracy desired, but in all cases a minimum of three specimens from each fabric or treatment should be tested. 9 Evaluation 9.1 The water penetration as indicated by the increase in mass of the blotting paper during the 5 min test period is calculated, and the average for at least three test specimens is reported. Individual determinations or average values of over 5,0 g may simply be reported as 5 g or >5 g. 9.2 In order to obtain a complete overall picture of the penetration resistance of a fabric or fabric combination, the average penetrations with different pressure heads on the nozzle should be obtained. The pressure head should be varied by 300 mm increments in order to determine: a) the maximum head at which no penetration occurs, b) the change in penetration of water with increasing head, and c) the minimum head required to cause “breakdown”, i.e. the penetration of more than 5 g of water. At each pressure head, a minimum of three specimens should be tested in order to obtain the average penetration for that head.