What happens when potassium iodide is added to a disulphide?

KISS.
K.S. Nagabhushana


What goes into making a pencil

I am sure you would have used a pencil in the recent past. Whether it was just to doodle something or to take down notes, the pencil is an excellent tool to make a marking that is not permanent. Pencils are usually made of graphite or in some cases coloured pigment or charcoal, encased in a wooden cylinder. It can be used for writing, marking and drawing.

The history behind pencil

The ancient Romans and Egyptians used a thin metal rod known as a stylus to make marking on their scribes which were made of papyrus, one of the earliest forms of paper. Since the styluses in ancient times were made of lead, the name has been carried forward today. And we still call it a ‘lead pencil’ even though pencils today are made of graphite and contain no lead at all.

How are pencils made?

The first step to making a pencil is to grind the graphite and mix it with clay and water in varying proportions. Once you do this you get a paste which is fed into metal tubes to form the graphite core of the pencil.

Cedar wood is usually used to make pencil casings.

To make smooth pencil leads the graphite tubes are superheated. Cedar wood is usually used to make pencil casings. The casing is made with several long grooves into which the graphite rods are fitted. The final touches to the pencil are to add things like erasers and pencil grips to the pencil.

Classification of pencils

Pencils are classified by their darkness. ‘H’ standing for hardness and ‘B’ for blackness with 9B is the lightest and 9H the darkest. The softness or hardness of the graphite determines the shade of the pencil. The harder the graphite the lighter the pencil.

Types of pencils

Today there are so many different types of pencils based on the material they are made of and their use. There are the normal graphite pencils, charcoal pencils used by artists, carbon pencils, coloured pencils, grease pencils with which you can write on almost any surface, watercolour pencils, and mechanical pencils. On the basis of their use there are carpenters pencils, golf pencils, copying pencils and erasable colour pencils.

Tags :     Everyday Chemistry     Graphite     Pencils     Stylus     Carbon    


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