On a sheet of copper, which I bevel, polish, and clean, I apply an acid-resistant coating (the ground). Using a rounded needle, I draw through the ground, exposing, while not scratching, the shiny surface. I usually work on location, as I do with painting, and do the initial needling as I look at the scene before me.
When the plate is submerged in the etchant (ferric chloride), every mark that I made interacts with the solution, while parts covered by the ground are not affected.
The chemical reaction* causes each exposed mark on the copper to become eroded (etched).
To print, I apply ink to the plate, and wipe it off the surface, leaving ink in the grooves.
On the press, a dampened piece of fine cotton-rag paper is placed over the inked plate, protective blankets of wool felt are placed on top, and then all is squeezed (pulled) under high pressure between heavy steel rollers.
The pressure forces the paper into the grooves, transferring ink to paper.
Each etching requires the plate be inked, wiped, and printed by hand, and so the resulting impression (no two are exactly the same) is accurately designated an original print (as opposed to a photomechanical reproduction, such as that produced by computer and ink-jet printer. Buyer beware).