DETERMINATION OF THE RESISTANCE OF FABRICS TO SURFACE WETTING. SPRAY TEST
This standard specifies the spray test method for determining the resistance of any fabric to surface wetting by water. This tissue may or may not have received water-repellent treatment.
It is not applicable for the determination of resistance to rain penetration in the fabric.
A specific volume of distilled or deionized water is sprayed on the sample, which is placed in a circular frame at 45º from the vertical so that its center is at a specific distance from the sprayer. The degree of wetting is measured by visually comparing the appearance of the sample with the descriptive patterns and photographs.
Spray devices: this is a funnel of 150 ± 5 mm in diameter held vertically with a spray rosette. This is attached to the end of the funnel by a rubber tube of 10 mm diameter (see image)
Metal spray rosette: composed of a perforated convex face with 19 holes of 0.86 ± 0.05 mm in diameter. The draining time for the volume of 250 ± 2 ml of water poured should be between 25 and 30 s.
Specimen holder: two metal or wooden rings that fit together. One must have an internal diameter of 155 ± 5 mm and the other an external diameter of 155 ± 5 mm in order to be able to fix the specimen between them. During the test, these rings shall be placed on a suitable support so that they are inclined 45° with the centre of the specimen at a distance of 150 ± 2 mm below the face of the spray rosette.
The specimens are conditioned according to ISO 139 minimum 4h.
At least 3 square specimens of 180 mm on a side are prepared from different areas of the fabric so that they are as representative as possible of the material. They will not be prepared from wrinkled areas or with folding marks.
Once conditioned, the specimens are mounted on the specimen holder and placed on the holder so that the fabric bundle is facing upwards. Unless otherwise specified, the warp must be parallel to the water draining on the specimen.
250 ± 2 ml of water is poured into the funnel quickly and regularly so that the spray is continuous. This duration must be between 25 and 30 seconds.
Immediately after spraying, the specimen holder is removed from the holder. The specimen holder is held by the lower edge, with the tissue plane almost horizontal and the fabric bundle turned downwards. The specimen holder is vigorously tapped against a solid object with the fabric towards the object. We rotate the specimen holder 180º and strike vigorously once again.
Immediately afterwards, the degree of wetness of the specimen face is assessed.
The grade that best matches the degree of wetting of the specimen described in the wetting scale (1) or the photographic reference pattern of wetting degrees (see image) is assigned. Intermediate grades with increments of 0.5 can be used for a grade 1 according to ISO i AATCC 50 specification or higher.
