Lithography (平版印刷术) is an art process of printing from a plane suce on which the image to be printed is ink-receptive and the blank area ink-repellent. Lithography is based on the antipathy of oil and water. A drawing is made in reverse on the ground suce of the stone with a crayon or ink that contains soap or grease. The image produced on the stone will accept printing ink and reject water. Once the grease in the ink has penetrated the stone, the drawing is washed off and the stone kept moist. It is then inked with a roller and printed on a lithographic press. As a process, lithography is probably the most unrestricted, allowing a wide range of tones and effects. Several hundred fine prints can be taken from a stone. The medium was employed by many 19 ^th century artists, including Goya, Delacroix, Daumier, Degas, and remains popular with contemporary artists. Among American artists noted for their lithographs are Currier and Ives.
The Currier and Ives firm of lithographers was founded Nathaniel Currier in 1834. James Ives joined the firm as a bookkeeper eigh years later just after becoming Currier"s brother-in-law, and was made a partner in 1857. The pair showed an uncanny (神秘的) ability to predict what the American public would rash to buy in the way of cheap art, and literally hundreds of thousands of prints from as many as 7,000 individual pictures were turned out and sold from the firm"s shop in lower New York by street vendors and over shop counters throughout the country and even in Europe. Though in the course of time the firm employed some of America"s finest artists, artistic excellence could certainly not be counted among the firm"s real goals.
Nevertheless, some time after it went out of business in 1907, the prints enjoyed new popularity as collectors" items, the rarer examples fetching thousands of dollars in the 1920"s. Which of the following can be inferred from the passage