hectograph

A hectograph is a duplication device that was popular in the late 19th and early 20th centuries, used for making copies of documents or drawings. It works by using a gelatin-based pad that can absorb ink from a master copy. This master copy is typically written on a piece of paper using special hectograph ink, which is alcohol-based.

When the inked paper is pressed onto the gelatin pad, the ink transfers to the pad's surface. Subsequent blank sheets of paper are then pressed onto the inked pad, transferring the ink and creating copies. The number of copies that could be made from a single master varied depending on the quality of the ink and the pad, but generally ranged from a few dozen to around fifty.

Hectographs were a relatively inexpensive and simple method for reproducing documents before the advent of modern photocopiers and offset printing. They were commonly used in schools, offices, and by small organizations. The process was somewhat messy, and the ink colors were often limited to purple, blue, or red. After use, the gelatin pad could be wiped clean and reused, or sometimes a new pad would be prepared. The hectograph itself consisted of the gelatin pad, often contained within a shallow tray, and a cover to protect the pad.