Etching is a type of printmaking. A copper (sometimes zinc or iron) plate is covered with a fine layer of acid-resistant material – this is called the ground. The actual image is scratched onto the ground with a sharp tool. The entire plate is then submerged in a bath of acid. The acid eats into the metal only in the areas where the acid-resistant substance has been scratched away. The longer the plate is left in the acid, the deeper the acid etches into the metal.
At this point the artist covers the plate with printers ink and wipes it hard with a cloth. This process removes all the ink from the majority of the surface, while also pushing it deeper into the grooves left by the acid. The amount of ink left is crucial, as too much can cause smudging, while too little produces a week and faint image.
Finally the artist lays a damp piece of paper over the plate and passes the whole thing through a printing press. The paper is pressed into the inked grooves, transferring the image from the plate to the paper.