SHELL & RAINWEAR
Water Column and Breathability
A fabric ’ s impermeability is measured in millimetres water column ( mmwc ). This is measured by stretching 10 cm2 of fabric over an equally large tube . The tube is filled with water and the height of the water column is measured when the first drop of water penetrates through the fabric . A fabric is classified as waterproof when it has a water column of 2,000 mm or more . A fabric ’ s breathability is measured in grams per square metre in 24 hours ( g / m2 / 24 hrs or MVP ). The higher the value , the easier it is for the fabric to allow excess humidity and water vapour to evaporate . These two values are both needed in order to determine a garment ’ s properties . A high water column / denser fabric can have poor breathability . A garment with good breathability is more comfortable to wear and helps prevent the garment from feeling damp inside .
Taped Seams
For the garment to be considered completely waterproof , the garment ’ s seams must be taped otherwise water will penetrate through the seams . This means that a tape is placed over the seams inside the garment . Completely waterproof garments have all seams taped and water-resistant garments have the most critical seams taped . Using a jacket as an example , the seams over the shoulders as well as the front and back seams , which are at risk of being exposed to the most moisture , are taped .
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