This is my only metal etching, which is a fascinating enough process to be told in detail.  To start, our class ventured outside and made several sketches of our school surroundings; this happened to be a pipe by the industrial arts wing.  These drawings were then etched onto primed metal plates about 5x8" large.  The plates were dipped into acid, burning grooves in the scratched areas where the metal became exposed.  Finally, the plate was inked, its surface cleaned, and several passes were made through the printing press, transferring the design onto paper.