In his later years, Corot began to soften his style. He paid ever more attention to the value of shading. His technique was more flexible, resulting with experiments in rendering light both in his paintings and his drawings. In 1853, he began making a series of visits to the English Channel, in which his use of charcoal emerged.
With his friend Constant Dutilleux, a lithographer, Corot began experimenting with a new process called cliché-verre. It was a new technique that combined photography and lithography. Corot produced sixty-six plates, however, he left the printing to others. Inspired by the Roman countryside, Corot’s most notable clichés-verre were The Gardens of Horace, Souvenir of Ostia, and The Banks of the Po River, completed between 1855 and 1858.
Cliche-verre was a new reproductive engraving technique discovered by his friend, Dutilleux, around 1853. This process combined photography and lithography. A plate of glass was first coated with printer’s ink with a lithographic roller, and then sprinkled with talc to quicken the drying time. The artist then drew on it with an engraver’s needle. A piece of sensitive paper was applied to the plate and then exposed to sunlight. This technique, unfortunately, only produced two or three proofs. Corot, always the fastidious craftsman, executed remarkable results. However, they never had the pristine beauty of the etchings and lithographs that he rendered toward the end of his life. There are but a handful of his etchings, but no one surpassed his mastery of this art, as a result of his endless quest for harmonious tonal values.