Very informative short film on the principles of rotogravure produced by Chevrolet in 1938.
more at http://news.quickfound.net/journalism_news_and_links.html "Principles of engraving are dramatized, showing that the tones of pictures result from high and low places on the engraver's plate." Public domain film from the Library of Congress Prelinger Archive, slightly cropped to remove uneven edges, with the aspect ratio corrected, and mild video noise reduction applied.
"Rotogravure (Roto or Gravure for short) is a type of intaglio printing process; that is, it involves engraving the image onto an image carrier. In gravure printing, the image is engraved onto a cylinder because, like offset printing and flexography, it uses a rotary printing press."
you might also like
The Beauty of Engraving
Letterpress 101
Pressless etching