A method of engraving in a steel plate, which allows for finer detail and many more impressions than does copper, was developed by Thomas Lupton in 1822. The plate is then dipped in acid, which bites into the exposed lines, thus etching the design into the plate. After dipping the plate in acid, sections of the design can be stopped out with varnish and the plate immersed in the acid again. This creates a deeper bite, and thus darker lines, for those areas not stopped out. Etching is an intaglio process, so prints made in this manner will have a platemark.
Etching allows for a freer artistic hand than does engraving.
The etching process was invented around the fourteenth century as a method of making decorations on armor. The earliest known printed etching was by Urs Graf and is dated 1513. The technique was perfected in the middle of the seventeenth century by Rembrandt. Aquatint An aquatint is created by etching sections, rather than lines, of a plate in order to create areas of uniform tone. An aquatint is prepared by applying resin or a similar ground to a metal plate, which is then heated, thus adhering the ground to the metal.