"[Jackson] Pollock would often begin with some sort ... Letters and numbers, moreover, frequently appear in works of the early 1940s." It may not be possible to answer the question definitively ...

Jackson Pollock and Lee Krasner Papers ... Starting in the late 1960s, Claessens began producing machine-primed canvases, and by the early 1970s all their canvases were machine woven and machine ...

By the early 1950s though, Pollock was stuck in a rut ... “If it hadn’t been for Lee Krasner, Jackson would not have been the power he was.” There was a time when Pollock was a nobody ...