Hydrostatic pressure testing might sound complicated, but it really isn’t. It’s just a test to find out how much pressure is required before a leak starts to occur. Hydrostatic pressure testing works on all types of fabrics, including those treated with a water-resistant or water-repellent finish. Read on to learn more about water resistance and hydrostatic pressure testing for fabrics and textiles.
Why Do We Test For Water Resistance?
Water resistance testing measures the protective qualities of fabric when exposed to moisture. The test is performed on fabrics used for rainwear, gowns, drapes, boat covers, and barrier fabrics in industrial applications. Water resistance depends on the repellency of the fibers and yarns, as well as the fabric construction. This test works on all types of fabrics, including those treated with a water-resistant or water-repellent finish.
Coated or laminated fabrics, such as TVF’s nylon mid-weight waterproof breathable, will have higher hydrostatic pressure testing ratings than fabrics only treated with a water-repellent finish, such as SunMaster.
How Do We Test For Water Resistance?
The fabric is secured in a special hydrostatic pressure testing machine.
One surface of the fabric is subjected to hydrostatic pressure, increasing at a constant rate.
When three points of leakage (water droplets) first appear, the test is stopped and the results are recorded. The hydrostatic pressure test is repeated at least three times and the results are averaged.
Hydrostatic Pressure Test Results
SunMaster has a hydrostatic head (HH) of 800+mm. This means that 800 mm of water could be accumulated in a column of water on SunMaster before any leakage would occur.
Note: A fabric with a waterproof breathable coating will have a much higher result.
Note: Excessive handling, folding, or contamination of the area to be tested might negatively affect the results of the test.
Hydrostatic Pressure Testing Tips From a TVF Expert
Remember, waterproofness is a function of the type and weight of coating and construction of the fabric.
The WPB fabric is much lighter and has a much tighter weave allowing for the coating to have better surface area coverage. Think of putting a coating over burlap versus a high count taffeta.
Lighter and tighter constructed fabrics need less coating weight to achieve the same performance of a heavier and looser weaved fabric.
We can also calender fabrics prior to coating to create a greater surface area and close the gaps between the intersecting points of each denier in order to achieve a higher rating with less coating or even higher rating with a greater amount of back coating.
AATCC 127 is a popular test because it more closely represents what happens in real world end-uses. Water is spread over a larger area with a lower rate of pressure.
The hydrostatic pressure test AATCC 127 tests what amount of pressure is needed to cause fabric to leak fluid. This could be a very important test for some industrial applications, depending on end-use.