When did GBT first use Zipatone to add grays to the artwork? Is he now using a digital equivalent?
The first Zipatone screen showed up in 1972. For the following year and a half, the Zipatone was usually a diagonal line pattern intended to mimic the original hand-drawn shading technique. In early 1974, the screen that is still in use was introduced. Since then there has been only one other screen added — the gradated pattern, used first in late 1988. The screens are not applied digitally.
