Etching became the printing process most attractive to artists from the mid 19th century, as it allowed dramatic contrasts between delicate and heavy lines, and had the spontaneity of sketching. The most famous artist to use it was Rembrandt.
Etching is related to engraving and aquatinting and uses acid to make marks in metal printing plates.
An etching begins with a copper plate which is heated then covered with a thin layer of wax. Once cooled the wax is impervious to acid. The artist then draws on the surface with a sharp tool called a burin, cutting through the wax to expose the copper. The plate is dipped in acid and the longer it is left the wider and deeper the etched lines become. This means they will print more darkly and more thickly. The simplest way to keep some lines lighter or thinner is for the artist to recoat the etched lines with wax, then draw the other areas of the image.
Compared to engraving, etching allows the artist to draw quite quickly and freely and this means the images they create can have a sketchier feel.
Famous artists to use etching include Cruickshank in his caricatures , Rembrandt and Samuel Howitt's beautifully detailed etchings of animals from 1823: