Rab Hydrostatic Head Explained

The standard test for waterproofing is to build up water pressure on the surface of the fabric and measure how much it can withstand before it allows water to pass through. Imagine a very tall, open-ended laboratory test tube standing on the fabric and being slowly filled with water. As more water is added, the pressure on the fabric will slowly increase. When we talk about the level of waterproofness in a particular fabric, we are expressing the height of that column before the waterproofing surrenders e.g. 20,000mm. This measurement is known as the hydrostatic head. Out in the field, this pressure can manifest itself in a number of ways. The straps of your backpack, overfilled pockets, a climbing harness or just kneeling on the ground all increase the external pressure on the garment and it is often at these points of contact that moisture will seep through the fabric. In such cases, a high hydrostatic head may become a key factor in your buying decision. The trade off is, that in most cases, a high hydrostatic head results in a less breathable jacket. Learn more about the Waterproof Technologies we use in our gear 👇 https://rab.equipment/guides/waterproof-jackets Shop Men's Waterproof Jackets 👇 🛒 // https://rab.equipment/mens/waterproof-jackets Shop Women's Waterproof Jackets 👇 🛒 // https://rab.equipment/womens/waterproof-jackets #WeAreRab #TheMountainPeople #RabLab #HydrostaticHead