Edition
Elephant Folio
Very large book, usually about 23 inches tall. Also Atlas Folio, which is 25 inches tall.
Obviously, maps which emanate from these volumes are significantly larger than those normally available, and usually need special handling.
Engraving
Ephemera
Etching
The earliest form of the intaglio process, but the grooves in the plate are formed by the action of acid rather than by the engraver's burin.
It was originally used to decorate metals like silver and armoury. The metal was coated with a thin layer of acid-resistant black resin, and the etcher/artist then used a fine needle to scratch through and expose the plate where he hoped the lines would appear on the finished print. When he had completed his work the plate was exposed to acid, which bit into the exposed metal to create the incision.
The longer the metal was exposed to the acid, the deeper the incision, and hence the blacker the line on the finished print, because the line would hold more ink for transfer to the paper
