Gore-Tex is a waterproof, breathable fabric membrane and registered trademark of W. L. Gore & Associates. Invented in 1969, Gore-Tex can repel liquid water while allowing water vapor to pass through and is designed to be a lightweight, waterproof fabric for all-weather use. It is composed of stretched polytetrafluoroethylene (PTFE), which is more commonly known by the generic trademark Teflon. The material is formally known as the generic term expanded PTFE (ePTFE). History Gore-Tex was co-invented by Wilbert L. Gore and Gore's son, Robert W. Gore. In 1969, Bob Gore stretched heated rods of polytetrafluoroethylene (PTFE) and created expanded polytetrafluoroethylene (ePTFE). His discovery of the right conditions for stretching PTFE was a happy accident, born partly of frustration. Instead of slowly stretching the heated material, he applied a sudden, accelerating yank. The solid PTFE unexpectedly stretched about 800%, forming a microporous structure that was about 70% air. It was introduced to the public under the trademark Gore-Tex. Gore promptly applied for and obtained the following patents: , issued April 27, 1976, for a porous form of polytetrafluoroethylene with a micro-structure characterized by nodes interconnected by fibrils , issued February 5, 1980 on March 18, 1980 for a "waterproof laminate", together with Samuel Allen Another form of stretched PTFE tape was produced prior to Gore-Tex in 1966, by John W. Cropper of New Zealand. Cropper had developed and constructed a machine for this use. However, Cropper chose to keep the process of creating expanded PTFE as a closely held trade secret and as such, it had remained unpublished. In the 1970s Garlock, Inc. allegedly infringed Gore's patents by using Cropper's machine and was sued by Gore in the Federal District Court of Ohio. The District Court held Gore's product and process patents to be invalid after a "bitterly contested case" that "involved over two years of discovery, five weeks of trial, the testimony of 35 witnesses (19 live, 16 by deposition), and over 300 exhibits" (quoting the Federal Circuit). On appeal, however, the Federal Circuit disagreed in the famous case of Gore v. Garlock, reversing the lower court's decision on the ground, as well as others, that Cropper forfeited any superior claim to the invention by virtue of having concealed the process for making ePTFE from the public. As a public patent had not been filed, the new form of the material could not be legally recognised. Gore was thereby established