I was thrilled last week to be given the opportunity to revisit Disney's original Xerox "machine" in the old Ink & Paint Department on the Disney Studio Lot. This thing STILL WORKS, after all these decades.
Ub Iwerks had developed this "two room" contraption in 1959 in order to reproduce animators' drawings straight onto cels. The costly process of inking cels was eliminated. From then on Disney characters appeared with black outlines. Walt Disney was not happy originally with this new look, but when 101 Dalmatians was such a box office smash, Walt eventually accepted this new aesthetic.
The current Ink & Paint Disney department is very small. There is no need for production cels anymore, but special cels are still being painted for Disney employees.
Here is a link to a previous post on Disney's xerox:
https://andreasdeja.blogspot.com/2014/05/xerox.html