Why is graphite in pencils called lead

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Catherine O. This tightly packed arrangement of carbon atoms makes diamond the hardest naturally occurring material on earth. In contrast, graphite contains a stack of carbon sheets.

Each carbon sheet is one atom thick and consists of a hexagonal lattice of carbon atoms bonded together. Each carbon atom in the sheet is bonded to the three nearest carbon atoms. The carbon atoms within a sheet are very strongly bound together, but the sheets themselves are very weakly bound. As a result, it is very easy for one carbon sheet in graphite to slip past the other sheets. This slippery-sheet structure is what makes graphite so oily to the touch and makes it such a good material to write with.

Enjoy this article? Donald March 7, pm. Michael June 15, am. Sheogorath April 13, am. Lilianne April 23, am. In , Sir John Pettus wrote a book on metallurgy in which he described the Borrowdale mine as producing a type of lead, which was exploited by painters, surgeons and writers. Painters drew their preliminary sketches with it, surgeons used this "Black Lead" medicinally, while writers rejoiced in this new instrument that freed them from having to carry a bottle of ink.

For a few centuries after its discovery, the Borrowdale Black Lead remained the highest-quality deposit ever found. Besides its painting, writing and medical applications, graphite had very important strategic military functions in casting cannon balls and other metal objects. The English would not let their enemies use the pure Borrowdale graphite for many years. He ground low-quality graphite very finely, mixed it with finely-ground clay, fired the mixture at high temperatures, and finished by adding wax before inserting it into skinny wooden cases.

In , a pencil factory started operations near the Borrowdale graphite supply. In , it became the Cumberland Pencil Factory, which produced the Derwent pencils so much loved by school children.

However, even though writing pencils made of graphite were first used around , writing pencils that used lead were still in very common use in the 18th century. Because they were cheaper, even if they were toxic. But, you certainly wouldn't want to suck on a "lead" pencil if it really had lead in it.

In fact, lead pencils became extinct only in the early 20th century.