Copying pencil

A copying pencil, also indelible pencil, is pencil whose lead contains a dye. The lead is fabricated by adding a dry water-soluble permanent dye to powdered graphite—used in standard graphite pencils—before binding the mixture with clay.

Copying pencils were introduced in the 1870s, and were originally marketed for copying documents, especially for making permanent copies of a permanent original. This was achieved by creating a hand written document using a copying pencil, laying a moist tissue paper over the document and pressing down with a mechanical press. The water-soluble dye in the writing would be transferred in its mirror-image to the tissue paper, which could then be read in verso by holding it up to a light source. According to conservationist, Liz Dube, "By the 1870's, letter copying books became the ubiquitous copying tool for businesses. These volumes contained hundreds of leaves of thin tissue paper, often high quality Japanese papers, bound together for the purpose of bearing copies of outgoing correspondence and other business documents."