Everyone knows about the good old number 2 pencil. But who knows what that number 2 actually means? Have no fear, I've taken the time to research this pointless topic for your pleasure. First, a little history.
Today pencils are numbered and/or lettered to tell us how hard the lead is. The higher the number, the harder the lead, and the lighter the markings. However, it wasn't always this way.
The earliest pencils were made simply from filling a wood shaft with raw graphite. The hardness of the graphite would differ depending on the quality of the graphite, thus it was different depending on where the pencil was made.
The current style of making pencils was developed in 1794 by Nicolas-Jacques Conté (1755-1805). Conté, a painter, chemist, physicist, balloonist, and inventor, put into practice a new method of making pencils so that they would be much more functional.
The Conté Process, as it became known, mixes powdered graphite with finely ground clay. This mixture is then shaped into a long cylinder and then baked in an oven. The more clay that is added versus graphite the harder the pencil lead. In January 1795, Conté patented his method as patent number 32. (Pretty high up there!)
Conté's first pencils were numbered for varing degrees of hardness. As the Conté process made its way into the world, other pencil makers decided to use the same technique. Of course, like any product, each company came up with their own standards for how their product should be labeled.
To further complicate things, English pencil decided to use letters instead of numbers. Soft leads were labeled 'B' for black, and harder leads with 'H' for hard. For varying grades they would just add more letters, thus very soft was 'BB', very hard was 'HH', and extra hard was 'HHH'. Simple right?
Later they switched again to a combination of numbers and letters! Where you would see 2B, 9H, etc. Although more complicated, this system allowed for a much wider variety of grades to be made with no more than a two character description. This was the last major change in the English grading system, the same they use today.
Why an F and an HB? Who knows. They're crazy! Many of the United States companies use a number only system for writing pencils (1, 2, 2½, 3, 4), but the number letter combination for graphic and artist pencils. I guess they couldn't make up their mind.
The No. 2 / HB grade pencil is the middle grade and is the most commonly used pencil for generic use. Harder grades are used for drafting and engineering, while softer grades are used usually by artists.
Still to this day there is not a "universal" pencil grading method. The foolish pencil makers have yet to sit down and come up with one. We should lobby our governments.