Membrane, laminate, ePTFE – there are many terms describing even more functions. What are the essentials and, most importantly: what is behind all of this? In 1969, Bob Gore made a revolutionary discovery: he found out that the expanded polytetrafluoroethylene (ePTFE) contains over 1.4 billion microscopic pores per square cm and can durably withstand temperatures from minus 250 °C to plus 260 °C. The result is a durably waterproof, windproof and breathable GORE-TEX membrane. GORE-TEX Laminate – the secret lies in between The GORE-TEX membrane is neither a coating nor an impregnation; neither is it an outer fabric or an inner textile lining. Rather, it is hidden inside clothing and shoes, having been worked into the garment between the outer fabric and the inner lining. GORE-TEX membranes are waferthin films that can be permeated by water vapour, not, however, by drops of water. This is because the pores of a GORE-TEX membrane are 20,000 times smaller than drops of water, but 700 times larger than the pores of water vapour. In order to use GORE-TEX membranes for garments in the clothing industry, it first has to be laminated onto a support material, i.e. it has to be pasted or welded together: this combination of membrane and support material is referred to as laminate. Durably waterproof: the GORE-TEX membrane remains dry, even after decades! According to the DIN standard 61539, clothing is referred to as waterproof if it withstands the pressure of a 1.3 metre high column of water (a process for determining waterproofness). However, simply sitting down already creates a much higher pressure than this. Even under extreme circumstances, however, no water permeates the GORE-TEX membrane, and the body remains permanently dry – and, what is more, this quality is retained over decades. Warm, owing to the hedge principle: the GORE-TEX membrane is windproof. The structure of the GORE-TEX membrane is similar to that of a hedge. The wind is caught up entirely in the branching and thus averted from the body. As a result, the warming air layers close to the body remain intact, even in cold and stormy weather. Therefore, thanks to the GORE-TEX membrane, the body is kept permanently dry and warm. Protection against hyperthermia and hypothermia: the GORE-TEX membrane is breathable The pores of the membrane are approximately 700 times larger than those of water vapour molecules, which explains why water vapour, such as perspiration, can evaporate unimpeded. The humidity of the body has to be able to escape rapidly, not least to protect the body against hyperthermia and hypothermia. Even during extreme physical exertion, the GORE-TEX membrane ensures that water vapour is diverted rapidly away from the body – thus guaranteeing a comfortable body climate.