his Chinese paintings. Zhang directly told Picasso that he did not have the right brushes to do Chinese art. Ten years later, Picasso received a gift from Zhang– two Chinese writing brushes made from the hair of 2500 three-year-old cows. Forgeries Chang's forgeries are difficult to detect for many reasons. First, his ability to mimic the great Chinese masters: Second, he paid scrupulous attention to the materials he used. "He studied paper, ink, brushes, pigments, seals, seal paste, and scroll mountings in exacting detail. When he wrote an inscription on a painting, he sometimes included a postscript describing the type of paper, the age and the origin of the ink, or the provenance of the pigments he had used." Third, he often forged paintings based on descriptions in catalogues of lost paintings; his forgeries came with ready-made provenance. Chang's forgeries have been purchased as original paintings by several major art museums in the United States, including the Museum of Fine Arts, Boston: It can be hard to attribute works to Chang since his style was so varied. Not only did he create his own work as well as forging other artists, but others would forge his originals. Additionally, in China, "forgery" does not hold the same nefarious connotation as it does in Western culture. What would be considered illegal forgery in the United States is not necessarily as criminal in China. Actions he took to fall under the Western definition of forgery include aging work with electric hairdryers, and creating fake provenance with his collection of seals that he could use to mark past "owners" of the work. To further this provenance, his friend Puru would provide a colophon authenticating the work's imperial origins. Art historian James Cahill claimed that the painting The Riverbank, a masterpiece from the Southern Tang dynasty, held by the New York Metropolitan Museum of Art, was likely another Chang forgery. The silk the piece is painted on could be carbon dated to help authenticate it, however since there has been some restoration on it -- the border repaired and the painting remounted and reglued -- not only would getting a sample to test be difficult, but there would be no guarantee the sample only contains original material. Museum curators are cautioned to examine Chinese paintings of questionable origins, especially those from the bird and flower genre with the query, "Could this be by Chang Dai-chien?"