Only graphite pencils were made in the early days and the strip or lead consisted
of pure Cumberland graphite. This was simply cut to roughly the required shape and
inserted into the pencil groove. However, stocks of Cumberland graphite dwindled
in the early 1800s and imported graphite was used instead. This was often clogged
with grit and sand particles which had to be removed by crushing the graphite, then
sifting and cleaning it. The graphite particles were then heated and compressed
into oblong slabs.