Painted commercial signs long had a bad reputation and were considered to be vulgar as well as clumsily and crudely daubed images. But with the middle of the 19th century, as modern urban life was being analysed through literature, the people who strolled through Paris, all senses on the alert, or wrote her history ; and then poets and writers – all started to consider this primitive and uncivilised object with attention and curiosity, in order to write its history and define its visual and aesthetic characteristics. Art critics in their turn appropriated the signs and turned the genre into a critical category, which was used to evaluate the excesses and the daring of modern painting from Courbet to Manet, and then from Impressionism to Synthetism. This reversal of the sign’s symbolic value is not without a bearing on the taste the early 20th century avant-gardes demonstrated for urban sign systems.