Faber-Castell - Lead Hardness Scale Since 1910
In the early 16th century, in the northern English county of Cumberland, people discovered a shiny black mineral that was used for the precursors of the present-day pencil. They believed it to be a lead ore. It was not until the late 18th century that it was discovered to be pure carbon – as is diamond. The substance was named graphite, from the Greek “graphein” = to write. In the late 18th century it became possible to produce pencils in various grades of hardness by mixing the graphite with clay. The "lead" pencil never really had anything to do with lead, but the misleading name has been retained to this day.
Surprisingly, despite the long history of black lead pencils, there is no internationally standardized hardness scale. All pencil manufacturers work to their own hardness classifications.
The CASTELL® hardness scale to which pencils are manufactured within Faber-Castell has remained unchanged since 1910.
Degrees of Lead Hardness Alternatively Expressed in Numbers
Writing hardness is determined by the mix ratio of graphite and clay: The greater the graphite content the softer the lead and the higher the proportion of clay the harder the lead. The choice of hardness required by the user of the pencil is determined by the type of writing or drawing work, by the paper surface and by the “heaviness” of hand of the user. (A heavy hand might prefer softer leads, and a light hand may work well with relatively hard lead qualities.)
The number and lettering printed on the pencil represents the degree of lead hardness. This indicates how soft or hard the lead is and how dark or light the mark is on the paper. Again this all has to do with the mixing ratio of clay and graphite.
Faber-Castell applies the following designations:
H = hard
B = black = soft
F = firm
HB = hard black = medium hard
Degrees of lead hardness alternatively expressed in numbers:
1 2 2 ½ 3 4
2B B HB H 2H
Degree B is Equivalent to a No.2
Choosing Pencils With the Right Lead Hardness For You
The choice of hardness required by the user of the pencil is determined by the type of writing or drawing work, the paper surface and the "heaviness" of hand of the user.
The surface of the paper acts like a rasp, shaving off extremely fine particles of the lead as it writes. The rougher the paper, the more lead particles are worn off. In general, therefore, rough or hard paper requires a harder quality of lead and smooth or soft paper a softer quality lead.
A heavy hand might prefer softer leads and a light hand may work well with relatively hard lead qualities.