4.1 Materials less than or equal to 15 mm (0.59 in.) in thickness shall not be tested in accordance with this test method in order to avoid complete immersion of the specimens. This type of exposure is beyond the scope of this test method.
4.2 This test method is used to assess both the short-term water retention and the long-term water retention. The short-term water retention is assessed as the average of the water retained following partial immersion intervals of 0.75-h and 3.00-h, in kilograms per square meter (percent by volume) (for materials tested at 25.4 mm (1.00 in.) thickness). The long-term water retention is assessed as the water retained following a 168-h partial immersion interval, in kilograms per square meter (percent by volume) (for materials tested at 25.4 mm (1.00 in.) thickness).
4.3 Materials shall be tested at both actual product thickness and 25.4 mm (1.00 in.) thickness provided the materials can be cut to a thickness of 25.4 mm (1.00 in.) without changing the original character of the materials. If a product cannot be cut without changing the original character of the material, the corresponding information shall be provided in the test report. Results shall be reported on the basis of equal nominal wetted specimen surface area (in units of kilograms per square meter) for materials tested at actual product thickness and on the basis of equal specimen volume (in units of percent by volume) for materials tested at 25.4 mm (1.00 in.) thickness. If a product cannot be cut to a thickness of 25.4 mm (1.00 in.) or if the actual product thickness is less than 25.4 mm (1.00 in.) but greater than 15 mm (0.59 in.), the product shall only be tested at actual product thickness and results only reported on the basis of equal nominal wetted specimen surface area.
4.3.1 By reporting results on the basis of equal nominal wetted specimen surface area, specimens of different thicknesses can be compared equitably. For some specimens, the water intake and retention primarily depends on the nominal wetted surface area available for water intake.
4.3.2 By reporting results on the basis of equal specimen volume, specimens can be compared equitably using units that commonly are selected to represent results of water intake testing (percent by volume). For some materials, water intake and retention primarily depends on the volume of the specimen available for water intake.
4.3.3 In most cases water retention is a secondary performance characteristic that has an influence on a primary performance characteristic, such as thermal performance, surface accumulation of moisture (that will potentially contribute to fungal growth), or localized collection of electrolytes (that will potentially contribute to corrosion). Depending on the primary performance characteristic that is of interest, the preferred units for use in comparing the water retention of different materials will be either kilograms per square meter or percent by volume.
4.4 Immersion times in addition to those required by this test method shall be permitted to be selected provided that all parties involved are in agreement.
4.5 The water retention characteristi
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