thermotype

Century Dictionary and Cyclopedia

1. n. A picture-impression, as of a slice of wood, obtained by first wetting the object with dilute acid, as sulphuric or hydrochloric, then printing it, and afterward developing the impression by heat.

Wiktionary

1. n. An image (as for example of a slice of wood) obtained by first wetting the object slightly with an acid, then taking an impression with a press, and next strongly heating this impression.

GNU Webster's 1913

1. n. A picture (as of a slice of wood) obtained by first wetting the object slightly with hydrochloric or dilute sulphuric acid, then taking an impression with a press, and next strongly heating this impression.