Lab instruments to be used must be designed in such a way that they can meet the following conditions

• It must allow to fix the sample fabric in such a way that will remain horizontal
• The sample fabric must be subjected to a uniformly increasing water pressure from the top or bottom of the test tube
• No leakage of water at the edges.
• The tendency of water to seep near the edge of the specimen and clamp pressure is minimized
• Distilled water that should be kept at 20ºC, 12ºC, 27 ºC, the chosen temperature mast be indicated in the la lab report.
• The rate of increase of the water pressure should be 10 cm H²O/min ± 0.5 cm H²O/min or 60 cm H²O/min ± 3cm H²O (9.8 mbar H²O/min ± 0.5 mbar H2=/ min or 58.8 mbar H²O/min ± 2.9 mbar H²O/min
• There will be a pressure gauge connected to the bucket used.

• The simples conditioning and essay conditions must be according to ISO 139

• At least five samples will be taken from different parts of the fabric, so that they are as representative as possible of the textile article to be tested.

• For each tested sample, the distilled water must be changed.
• The sample fabric must be placed in the clamps, above the test cuvette.
• The possible penetration of water is continuously monitored
• The pressure is recorded in centimeters of conventional water column at the moment in which the third drop of water appears passing through the sample fabric.
• The precision of the recorded pressure measurement must be:
• Do not take into consideration the very fine drops which don’t make the volume to increase, and successive drops through the same point of fabric.

The mean of the pressures recorded for the specimens submitted to the test will be calculated, according to chapter 7. The individual results and the average result expressed in centimeters of conventional water column will be recorded.

1. 670(cm/H²O)