Carlson wrote over 400 ideas for new inventions in his personal notebooks while working at Bell Labs. He kept coming back to his love of printing, especially since his job in the patent department gave him new determination to find a better way to copy documents. "In the course of my patent work," wrote Carlson, "I frequently had need for copies of patent specifications and drawings, and there was no really convenient way of getting them at that time." At the time, the department primarily made copies by having typists retype the patent application in its entirety, using carbon paper to make multiple copies at once. There were other methods available, such as mimeographs and Photostats, but they were more expensive than carbon paper, and they had other limitations that made them impractical. The existing solutions were 'duplicating' machines—they could make many duplicates, but one had to create a special master copy first, usually at great expense of time or money. Carlson wanted to invent a 'copying' machine, that could take an existing document and copy it onto a new piece of paper without any intermediate steps.