The 1880s saw a new stage in Renoir's work. Under the influence of scientific theories about the interaction of spectral colours, which stated that it was necessary to paint in tones of the pure spectrum only, the colouring in his pictures changed radically. The artist renounced black completely, replacing it by a complex mixture of blue ultramarine and red madder. Although the heroines in his pictures remained the same as ever, young Parisiennes and women of Montmartre, at the beginning of the 1880s the artist's pictorial manner lost its former Impressionist "atmospherics" and became more austere and graphic. "I have come to the end of Impressionism," Renoir acknowledged.