The coated fabric used by ORTLIEB – including all welded seams – continues to resist leaking when exposed to a 100,000 mm column of water! This extreme degree of waterproofing is achieved using a process known as high frequency welding (HFW). Instead of applying heat from the outside, HFW involves the application of high frequency voltage to the objects that need to be welded. The voltage causes the molecules within the various materials to vibrate and, essentially, to generate heat. Softened from within by the heat, the materials are then bonded under high pressure, leaving the welded seam at least as strong as the surrounding material.