I remember after Knuth finished designing fonts that he was happy with and people were starting to expect he'd get back to work on the next volume of TAoCP now that he was happy with typesetting and fonts one of the major computer magazines (Dr. Dobb's or Byte I think) published an article in the April issue that said TAoCP was again delayed because Knuth was not happy with the ink and was designing a program to develop better ink formulations.