During the First World War, women around the world started to shift to shorter hairstyles that were easier to manage. In the 1920s women started for the first time to bob, shingle and crop their hair, often covering it with small head-hugging cloche hats. In Korea, the bob was called . Women began marcelling their hair, creating deep waves in it using heated scissor irons. Durable permanent waving became popular also in this period: it was an expensive, uncomfortable and time-consuming process, in which the hair was put in curlers and inserted into a steam or dry heat machine. During the 1930s women began to wear their hair slightly longer, in pageboys, bobs or waves and curls.