In 1960, Andy Warhol began producing his first canvases, which he based on comic strip subjects. In late 1961, he learned the process of silkscreening from Floriano Vecchi who had run the Tiber Press since 1953. Though the process generally begins with a stencil drawing, it often evolves from a blown up photograph which is then transferred with glue onto silk. In either case, one needs to produce a glue-based version of a positive two-dimensional image (positive means that open spaces are left where the paint will appear). Usually, the ink is rolled across the medium so that it passes through the silk and not the glue.
Although Warhol had produced silkscreens of comic strips and of other pop art subjects, he supposedly relegated himself to soup cans as a subject at the time to avoid competing with the more finished style of comics by Roy Lichtenstein. In fact, he once said "I've got to do something that really will have a lot of impact that will be different enough from Lichtenstein and James Rosenquist, that will be very personal, that won't look like I'm doing exactly what they're doing." In February 1962, Lichtenstein displayed at a sold-out exhibition of cartoon pictures at Leo Castelli's eponymous Leo Castelli Gallery, ending the possibility of Warhol exhibiting his own cartoon paintings. In fact, Castelli had visited Warhol's gallery in 1961 and said that the work he saw there was too similar to Lichtenstein's, although Warhol's and Lichtenstein’s comic artwork differed in subject and techniques (e.g., Warhol’s comic-strip figures were humorous pop culture caricatures such as Popeye, while Lichtenstein’s were generally of stereotypical hero and heroines,inspired by comic strips devoted to adventure and romance). Castelli chose not to represent both artists at that time, but he would, in 1964, exhibit Warhol works such as reproductions of Campbell's Juice Boxes (pictured below right) and Brillo Soap Boxes. He would again exhibit Warhol's work in 1966. Lichtenstein's 1962 show was quickly followed by Wayne Thiebaud’s April 17, 1962 one man show at the Allan Stone Gallery featuring all-American foods, which agitated Warhol as he felt it jeopardized his own food-related soup can works. Warhol was considering returning to the Bodley gallery, but the Bodley's director did not like his pop art works. In 1961, Warhol was offered a three-man show by Allan Stone at the latter's
Irving Blum was the first dealer to show Warhol’s soup can paintings. Blum happened to be visiting Warhol in May 1962, at a time when Warhol was being featured in a May 11, 1962 Time Magazine article "The Slice-of-Cake School" (that included a portion of Warhol's silkscreened 200 One Dollar Bills), along with Lichtenstein, Rosenquist, and Wayne Thiebaud. Warhol was the only artist whose photograph actually appeared in the article, which is indicative of his knack for manipulating the mass media. Blum saw dozens of
Article Source : http://en.wikipedia.org/wiki/Campbell's_Soup_Cans