From the 1920s, simple all-in-one swimsuits in clinging machine-knitted wool jersey became fashionable, and were retailed by specialist firms such as Jantzen and Bukta. Stylised female figures in stylish swimming costumes were also used to decorate or advertise products by connecting them to healthy leisure pursuits, and the outdoor life (see the fan below). The first 2-piece swimsuits or "bikinis" revealing a bare midriff were worn from the late 1930s, although the term "bikini" was not used until after the war in the late 1940s. By the 1950s and 1960s, the fabric used for swimwear increasingly reflected mainstream fashion and costumes became more daring and vibrant, so that even a swimsuit from M&S would be made in a dramatic psychedelic print to attract the youth culture.
By the mid-1960s more and more bare flesh was exposed, and women's swimwear could be very revealing. Avant guarde designers like Rudi Gernreich produced ever bolder styles which were featured in fashion magazines, notably his outrageous topless "Mono-kini" of 1964. Later designs included one-piece suits with bold, geometric cut-outs, revealing much of the wearer's body, and asserting that the body should be flaunted, not carefully covered up.
Full item descriptions:
"bathing costume & swimsuit" [1983.371], Jantzen
"bathing costume & swimsuit" [1989.63], St Michael, Marks & Spencer
"bathing costume & bikini" [1947.2865]