Like his family before him, Karl was inspired by the zeitgeist. In this case the impact of brutalism in modern architecture. In 1963, BIRKENSTOCK released a sandal where the structure and construction of the product was visible and integral to the design, which is a perfect reflection of brutalism. The flexible footbed with the cork-latex core was the basis of the sandal, and it featured a simple adjustable strap. Again BIRKENSTOCK was ahead of its time. While shoe fashion in the 1960s was influenced by the Italian stiletto, the avant garde modernity of Karl’s sandal was not accepted by the mainstream. It launched at the 1963 shoe trade fair in Düsseldorf, but turned out to be a failure. The first path to success would clearly not come through fashion, but from the success that had already been developed within the health care system.
Karl Birkenstock made doctors his partners in spreading the word about the shoe. He produced a pamphlet, distributed in a medical journal, in which he offered to provide free samples of the Madrid sandal. He was soon swamped with orders from healthcare workers. This was just the beginning. The rapidly changing lifestyle of the 20th century meant people had more leisure time, much of which was spent at home. With comfort more important than style for at-home footwear, people turned to BIRKENSTOCK as the obvious choice. The footbed sandal was also taken up by members of various subcultures, who expressed their unconventional thinking by wearing the sandal that also broke all conventions. Initially referred to only by product numbers, which ran from 410 to 431, the model was renamed the Madrid sandal in 1979. True to the company’s principles, it was crafted entirely from natural materials. The unique and avantgarde design remains almost unchanged to this day.