The graphite pencil scale is a system that grades pencils according to how hard the pencil lead is and how dark or black is the mark that it produces on the paper. The gradings on the scale are sometimes referred to as degrees of hardness and currently, there are 24 degrees on the graphite pencil scale ranging from 10H -12B.
In this guide we explain why there are 24 degrees of Hardness on the Graphite Pencil Scale, what are H & B & how this relates to the U.S Pencil Hardness Scale. As well as what percentage of graphite is in pencil.
Table of Contents
- 1 The Graphite Pencil Scale H & B Numbers
- 2 What is an F Grade Pencil?
- 3 The U.S Pencil Hardness Numbering System
- 4 How Much Graphite is in a Pencil?
- 5 What is the Hardest Pencil Grade?
- 6 What is the Softest Pencil Grade?
- 7 Are all Graphite Pencils the Same Darkness?
- 8 The Pencil Lead Hardness Scale
1. The Graphite Pencil Scale H & B Numbers
As you can see from the diagram of the graphite pencil scale it comprises numbers and the letters H and B which represent hardness, blackness, and the letter F which we will explain in more detail a little later.
To get a better understanding of what the letters H and B mean on the scale we first need to explain what are the materials that make up the core of a pencil.
First, let us get the elephant out of the room people often refer to pencils as lead pencils which infers that the core of a pencil is made of lead. This is not true, and it is historical dating back to the 1500s when graphite was first discovered. It was wrongly assumed that it was a type of lead and was centuries later before it was correctly identified as a form of carbon known as graphite. For more information check out our guide What is Pencil Lead Made of? Where we go into this in a lot more detail.
The core of a wooden pencil is made from two components graphite which is a very soft dark greasy material and clay which is a type of soil made up of several different minerals. Pure graphite is very soft and leaves a dark mark when rubbed against the paper. Whereas clay is very hard and leaves a light grey mark when rubbed against the paper.
The clay is used as a binder to hold the graphite together as it would be too soft to use on its own. By altering the ratio of graphite to clay you are changing the properties of the pencil core. If you have a high portion of clay the core of the pencil is very hard and leaves a lighter grey mark on the paper. This equates to the H or hardness letter on the pencil graphite scale.
And if you reduce the proportion of clay to graphite in the core of the pencil it is now a lot softer and will leave a darker black mark. This equates to the B or Blackness letter on the pencil graphite scale.
HB is considered to be the middle point of the scale and the numbers represent either an increase in the blackness and softness of the core of the pencil i.e. B, 2B, 3B, B, etc. Or they represent an increase in the hardness of the core due to a higher ratio of clay to graphite producing lighter grey marks ie H, 2H, 3H, 4H, etc.
2. What is an F Grade Pencil?
If you refer back to our diagram of the graphite scale you can see that between the grades of HB and H is the F grade. As we have already discussed H and B refer to the hardness and blackness of the pencil so what is an F-grade pencil?
An F-grade pencil is classed as being firm and can be sharpened to a fine point. This makes it an ideal pencil for technical drawing. It is equivalent to a U.S 2 ½ pencil, which we will discuss in more detail in the next section.
3. The U.S Pencil Hardness Numbering System
When the U.S pencil manufacturers started making pencils they needed a way to categorize how hard or soft the graphite core of their pencils was. They did not adopt the European system but instead chose a numbering system to grade their pencils. Which is #1, #2, #2 ½, #3 & #4 with a number #1 pencil having the softest graphite core and #4 having the hardest graphite core.
The U.S pencil hardness scale roughly equates to the pencil graphite scale as:
- U.S #1 – Graphite Pencil Scale B
- U.S #2 – Graphite Pencil Scale HB
- U.S #2 ½ – Graphite Pencil Scale F
- U.S #3 – Graphite Pencil Scale H
- U.S #4 – Graphite Pencil Scale 2H
The U.S pencil manufacturers still use this numbering system which is marked on their pencils that are considered for general purpose and office use. However, they use the pencil graphite scale for all other pencils that are either designed to be used for artistic or technical drawing.
4. How Much Graphite is in a Pencil?
The very first pencils were made of unrefined graphite that was mined from a deposit of graphite unearthed in England in the early 1500s. The quality and consistency of these early pencils were not very good, and they were prone to easily breaking. The breakthrough came in 1795 when due to an English Embargo there was a shortage of graphite in France. Nicolas-Jacques Conté developed a manufacturing process where he could make mass produce pencils using less graphite with a consistent amount of hardness and blackness.
He achieved this by grinding graphite and clay into a fine powder and then placing it into molds that he then baked in an oven. By altering the ratio of the clay to the graphite he could alter the pencil’s characteristics as to how hard the core was and how dark it wrote. This became known as the Conte Process and it is still the same technique that is used to manufacture pencils today.
It is also how the first pencil grading system started as Conte made 4 pencils with different hardness levels which he numbered 1 to 4 with 1 being the hardest and gradually getting softer.
The manufacturers are very secretive about the formulas that they use to make their graphite pencil cores. This it makes a little difficult to find out the percentage of graphite in pencils. However, in 2000 Maria Costa Sousa and John W Buchanan manage to obtain this information from the pencil manufacturers. They published it in the computer graphics forum as part of a report called The Observational Models of Graphite Pencils.
As you can see from the table a 9H pencil has approximately 41% graphite, 53% clay, and 5% wax for lubrication. At the other end of the scale, an 8B pencil has 90% graphite, 4% clay, and 5% wax.
What is interesting is that there is 68% graphite in HB pencils which are the most popular general-purpose pencils for schools and offices etc. Considering that HB is deemed to be the middle of the graphite pencil scale then you would expect it to have 75% graphite which is halfway between the hardest (90% graphite) and softest (41% graphite).
However, when you refer to the table then the pencil grade with 75% graphite is between 2B and 3B.
5. What is the Hardest Pencil Grade?
The hardest pencil grade is 10H if you refer to the previous table which lists the ratio of graphite to clay in pencils then you can see that it will have a ratio in the region of 38% graphite and 56% clay. Although quite a few manufacturers make 10H pencils the Staedtler Mars Lumograph 10H pencils are particular favored by draftsmen and architects.
This is because they have a specially formulated graphite core that is less scratchy. They are also highly break-resistant. During the manufacturing process, they use a property full-length bonding process where the graphite core is glued on all sides to the wood case that it is encased in.
6. What is the Softest Pencil Grade?
The softest graphite pencil grade is 12B and it is the Staedtler Lumograph 100 12B pencil. The next pencil with the highest B grade is the Mitsubishi HI Uni 10B pencil. There may not be a lot of difference between the blackness of these pencils as we explain in the next section.
If you would like more information, then check out our Complete Guide to the Darkest Pencil Lead. Where we go into more detail about these pencils, other specialty pencils including extra dark pencils as well as charcoal pencils, and drawing techniques to make your blacks appear even blacker.
7. Are all Graphite Pencils the Same Darkness?
All pencil manufacturers use the Graphite Pencil Scale to identify the different grades or degrees of hardness and blackness of their pencils with H, B, and a number. However, there is no international standard which means that an HB pencil from one brand may leave a different mark on the paper compared to a HB pencil from another brand.
The Japanese prefer their pencil to have a softer darker lead which means that an HB pencil from Mitsubishi or Tombow than a German pencil from Staedtler or Faber-Castell. In The U.S it varies by brand but an HB may be slightly softer and darker than a German HB pencil but nowhere near as dark as a Japanese HB Pencil.
8. The Pencil Lead Hardness Scale
As we mentioned earlier there is no lead in pencils it is historical due to when graphite was first discovered it was believed to be a form of lead hence lead pencil.
Even today people still refer to pencils as lead pencils and there are plenty of articles online wrongly calling the graphite pencil scale the pencil lead hardness scale or pencil lead softness scale. These articles lead to confusion with people then searching for graphite vs lead pencil when there is no such thing as a lead pencil.