e in the development of the style. Impressionists took advantage of the mid-century introduction of premixed paints in tin tubes (resembling modern toothpaste tubes), which allowed artists to work more spontaneously, both outdoors and indoors. Previously, painters made their own paints individually, by grinding and mixing dry pigment powders with linseed oil, which were then stored in animal bladders. Many vivid synthetic pigments became commercially available to artists for the first time during the 19th century. These included cobalt blue, viridian, cadmium yellow, and synthetic ultramarine blue, all of which were in use by the 1840s, before Impressionism. The Impressionists' manner of painting made bold use of these pigments, and of even newer colours such as cerulean blue, which became commercially available to artists in the 1860s. The Impressionists' progress toward a brighter style of painting was gradual. During the 1860s, Monet and Renoir sometimes painted on canvases prepared with the traditional red-brown or grey ground. By the 1870s, Monet, Renoir, and Pissarro usually chose to paint on grounds of a lighter grey or beige colour, which functioned as a middle tone in the finished painting. By the 1880s, some of the Impressionists had come to pre