Apart from a long hiatus from 1963 to 1972, Andy Warhol maintained a regular practice of illustration throughout his life. Drawing is the one medium that spanned the whole of his career, from his earliest days as an art student in the 1940s to the last few weeks before his death in 1987. His characteristic "blotted line" technique served him well, and often in commercial assignments. Warhol was in such demand for commercial assignments, especially for his illustrations of shoes, that in order to avoid turning down assignments, he recruited assistants to execute drawings under his direction and even had his mother hand-write some of his lettering. This working process would later form the foundation for calling his studio in New York City, the Factory.