I stumbled upon a catalog from Faber Castell which I consider to be very interesting, "Product Knowledge Manual".
The catalog starts with a short history of the company and its line. I like that the history was detailed and well documented.
I encourage you to read it but I will give below a short version presenting the important moments, so be aware, spoilers will come.
-In 1761 Kasper Faber produces a pencil in Stein and sells it in a market in Nuremberg.
-Then his son Anton Wilhelm Faber takes over and the workshop becomes A.W. Faber. After the business is taken over by Georg Leonhard Faber, but he doesn't do too well, as the business goes through rough times (political and economic difficult period).
-The son of Georg, Lothar von Faber takes over and develops the business.
He develops the modern quality pencil, sets the length and different grades of hardness that remain valid today, also it is the first time to produce a hexagonal section
The pencil is labeled A.W. Faber, becoming the world's first brand pencil. Also, he expands and founds a branch in New York, and subsidiaries in London, Paris, Vienna, St Petersburg.
-Wilhelm von Faber, the son of Lothar runs the company for a while.
-After Wilhelm's death, his daughter Baroness Ottilie von Faber marries Count Alexander zu Castell Rudenhausen. Lothar before his death through his testament assured that future generations will have to keep the Faber name. So after the marriage of Ottilie and Alexander, the family name became Faber - Castell. At this time the company became Faber-Castell.
In 1905 the green Castell pencil range is launched, with a new product logo "Tournament of the jousting Pencil Knights"
-Roland Graf von Faber-Castell, son of Ottilie and Alexander succeeds
-Followed by his son Anton Wolfgang Graf von Faber-Castell ran the company until 2016
-After his death, the company was taken over by a board of directors of which Countess Mary von Faber-Castell is part of
Indeed an interesting history. So between 1839–1896, Lothar the 4th generation of Faber's running the pencil business standardized what today is a Faber Castell pencil, the basic shape, and the lead hardness grade. In 1905 Alexander, the 6th generation made the traditional Faber Castell green.
They tell us that "the ideal writing pencil (for example in office) is the medium degree of harness so-called HB, while the school student's pencil has a B hardness degree.
I always thought that a #2 pencil is the equivalent HB, but apparently, it is B.
1 2 2 1/2 3 4
2B B HB H 2H
Faber Castell offers the model 9000 pencil in 16 degrees of hardness, which is awesome. Also, in the manual the diagram of the mixture between clay and graphite for all the hardnes's.
It is interesting as we can approximate the mixing of the two components to get the different hardness. Just at a glance, you can see around the HB is an inflection point where the increase of graphite in the composition is less and less. I mean that between a 2b and 4b the formula seems to be very similar.
Based on this graphic the composition rounded up to an integer. The b - 8b is increasing the graphite by an increment of 2 percent.
Also, the HB is not a 50% mix of the two but 66% of graphite and only 34% of clay.
This is true of course for Faber Castell as the hardness of the lead is not standardize, so different manufacturers can produce the HB pencils a bit different.