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. At the other end of the scale, an 8B pencil has 90% graphite, 4% clay, and 5% wax. They published it in the computer graphics forum as part of a report called The Observational Models of Graphite Pencils.Īs you can see from the table a 9H pencil has approximately 41% graphite, 53% clay, and 5% wax for lubrication.

However, in 2000 Maria Costa Sousa and John W Buchanan manage to obtain this information from the pencil manufacturers. This it makes a little difficult to find out the percentage of graphite in pencils.

The manufacturers are very secretive about the formulas that they use to make their graphite pencil cores. 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. This became known as the Conte Process and it is still the same technique that is used to manufacture pencils today. 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. 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. Nicolas-Jacques Contédeveloped a manufacturing process where he could make mass produce pencils using less graphite with a consistent amount of hardness and blackness. The breakthrough came in 1795 when due to an English Embargo there was a shortage of graphite in France. The quality and consistency of these early pencils were not very good, and they were prone to easily breaking. The very first pencils were made of unrefined graphite that was mined from a deposit of graphite unearthed in England in the early 1500s. However, they use the pencil graphite scale for all other pencils that are either designed to be used for artistic or technical drawing. 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. The U.S pencil hardness scale roughly equates to the pencil graphite scale as: 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. They did not adopt the European system but instead chose a numbering system to grade their pencils. 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. If you are unsure which pencil grades you need then check our guide How to Choose a Pencil. It is equivalent to a U.S 2 ½ pencil, which we will discuss in more detail in the next section. This makes it an ideal pencil for technical drawing. This equates to the H or hardness letter on the pencil graphite scale.Īn F-grade pencil is classed as being firm and can be sharpened to a fine point. 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. By altering the ratio of graphite to clay you are changing the properties of the pencil core. The clay is used as a binder to hold the graphite together as it would be too soft to use on its own. Whereas clay is very hard and leaves a light grey mark when rubbed against the paper. Pure graphite is very soft and leaves a dark mark when rubbed against the paper. 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. For more information check out our guide What is Pencil Lead Made of?Where we go into this in a lot more detail. 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. This is not true, and it is historical dating back to the 1500s when graphite was first discovered. 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.

Graphite pencil