Water Resistance, Water Resistancy | Determination of Water Resistance by Shirley Hydrostatic Head Tester

Name of the Experiment: Determination of water resistance by Shirley Hydrostatic Head tester.

The merit of a fabric intended for rainwear, wagon covers or tents is judged, amongst other properties, by its ability to keep water out; conversely, when intended for hose pipes or canvas buckets, to keep water in. In another direction, some fabrics must exhibit the ability to absorb water rapidly, toweling being an obvious example. So there is a relation between water and textile materials which is very necessary for their end use.

To measure the water resistance of the given fabric.

Water resistance is the force or pressure of water which it applied on textile material to keep out though it and the determination of this required pressure or force is very important for particular use of a fabric. Shirley Hydrostatic Head tester is used to determine this pressure of water. In this instrument the specimen holder consists a double-chambered cell; the internal diameter of the inner chamber is 5 cm. Circular specimens are clamped between rubber gaskets over the orifice. Compressed air enters the outer chamber through a tube B and displaced the distilled water contained in the chamber through communicating passages into the inner chamber, thereby forcing water up against the specimen. The clamp is provided with a skirt which prevents air from leaking continuously across the test specimen from inner to outer chamber or to the atmosphere. The tube is connected to a manometer and the pressure of water against the fabric is, for all practical purposes, the pressure shown on the adjustable scale mounted on one arm of the manometer tube. The air supply for the test is drawn from a reservoir of about 3 l capacity which is itself fed through a flow control device from a source which may vary between 4 and 20 in/lb2. The flow control device is so designed that once it has been set to give the required rate of increase of pressure of 10 cm of water per minute, the rate of loading will be within the specified limits of 10+/-0.5 cm/min up to the limit of the instrument. The maximum head attainable is 150 cm of water.

Spray tester
  1. Crease recovery tester
  2. Water
  3. Template
  4. Canvas fabric.
Spherical canvas fabric.
Size:       6 cm diameter.

Temperature – 25oC and relative humidity – 67%
Standard atmosphere: temperature – 20oC and relative humidity - 65%.

M/c specification:
Name: Shirley Hydrostatic Head tester
Brand: NEGRETTI & ZAMBRA, made in England. 
Capacity: 0-150 cm.  

Working Procedure:
  1. Circular specimens of 6 cm diameter are cut very carefully with as little handling of the fabric as possible.
  2. The test cell is rinsed with distilled water and filled up to approximately 0.3 cm of the top.
  3. The inner rubber gasket is thoroughly dried by wiping with a clean absorbent cloth and a test specimen is laid over the orifice.
  4. The dried clamp is placed in position and screwed down.
  5. The switch is turned to ‘Head’ position to start the compressor and then turned to ‘Test’ position.
  6. The pressure under the specimen is increased at a specified rate and until water appears minimum at the three places on the fabric, the switch will not be turned to ‘Head’ position.
  7. As soon as three drops of water appear on the fabric the reading is taken from the dial.
  8. In this way at least 10 readings are taken from 10 specimens and average pressure is then calculated.
Pressure in cm
Average pressure
Table: Pressures found from the test.

The water resistance of the sample fabric is 30.8 cm water pressure. As a result fabric will be water repellent.

According to the type of fabric the resistance of fabric varies between 0 -150 cm. The sample of the fabric is a canvas cloth and its water resistance is 30.8 cm. So it may say that the fabrics resistant to water is enough for its end uses. 
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Mazharul Islam Kiron is a textile consultant and researcher on online business promotion. He is working with one European textile machinery company as a country agent. He is also a contributor of Wikipedia.

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