Anastaticprinting

Anastatic printing, a method of reproducing drawings, engravings, or any printed matter, invented by Wood in 1841. The printed matter is first moistened with dilute phosphoric acid, which corrodes all blanks but does not affect the printed portion. The sheet is then transferred to a zinc plate, which takes a facsimile of the printed portion in reverse order. Gum and ink are then applied, then the acid and again ink, when an impression may be taken as clear as the original.