If you have ever look through some old pencils you’ll quickly find out that there were (and still are) many types of pencils aside from that standard #2 or HB one that got us all through elementary school. With that in mind, what is a copying pencil? What is an indelible pencil?
A copying pencil would generally be defined as a wooden pencil that is specially designed for use when mimeographing or in some way copying a document. The pencil’s lead has extra aniline (a component of the dye in the graphite) which could be wetted in order to aid the creating of copies taken from the original.
This dye also means that the pencil cannot be fully erased from paper, so the copying pencil was also a precursor to the ballpoint pen because it was easier to use than a fountain pen, which would have been the main alternative to a pencil prior to the ballpoint pen becoming popular in the 1950s.
The aniline dye is harmful to people so the pencils had problems even before the mimeograph was replaced by modern tools like the photocopying machine, but also the popularization of carbon copying paper meant that the copying pencil was starting to become outmoded by the 1950s or 60s.
The word “indelible” is used to describe something that leave writing or marks behind that cannot be erased or washed out. So, as you’ve guess, an indelible pencil is any pencil that cannot be erased, usually thanks to some form of dye in the pencil’s graphite. This pencil acted an alternative to a pen as it could not be erased or modified easily, and some were even used to sign checks and work similar documents where a signature or other important marks were needed.
An indelible pencil had to be resistant to erasing but didn’t need to be able to be copied.
These are sometimes known as “ink pencils” because the graphite has the indelible property of ink.