In 1770 Joseph Priestley, the English scientist who discovered oxygen and soda water, described ‘a substance excellently adapted to the purpose of wiping from paper the mark of lead pencil’. The substance, then known as ‘India gum’, he remarked, required rubbing action on the part of the user. He called it ‘rubber’. (In Britain, erasers are still often called rubbers.) Though Priestley discovered rubber’s erasing properties, it was Edward Nairne, an English scientific instrument maker, who is credited with developing and marketing it.

Until 1770 the preferred way of erasing pencil marks was breadcrumbs moistened and balled up. One day Nairne inadvertently picked up a piece of rubber instead of breadcrumbs to remove pencil marks and discovered rubber’s remarkable erasing properties. Quick to exploit his discovery, he began selling cubes of rubber at his London shop. Touted as erasers, they sold for an astonishingly high price of 3 shillings per half-inch cube. These expensive erasers posed problems for users: natural rubber is perishable, smelly and tends to rot. In 1834 Charles Goodyear, an American inventor, figured out how to make rubber stronger and more elastic.

In 1858 Hymen Lipman, an American stationer, patented a rubber-tipped pencil. These little erasers on pencil ends are known as ‘plugs’, and the metal bands that contain the plugs are called ‘ferrules’.

There is no toxic lead in lead pencils (the name comes from lead stylus used in ancient Rome). The core of pencils is made up of a non-toxic mixture of graphite and clay. By varying the graphite to clay ratio, the ‘hardness’ and ‘blackness’ of the core can be adjusted. When a pencil is put to paper, graphite particles mix up with the fibre particles that make up the paper. Polymers that make up an eraser are stickier than the particles of paper and so graphite particles end up getting stuck to eraser instead.

If you think that the delete key has made the eraser obsolete, you are wrong. The humble eraser is still the best tool for removing pencil markings, even 250 years after its discovery. A good old ‘plug’ made of rubber or a new high-tech eraser made of vinyl are worth ‘3 shillings’ only if they: (a) lift pencil marks from paper with the lightest touches without smudging and smearing; and (b) avoid paper trauma; that is, no matter how hard you rub, the paper stays hole-less.

© Surendra Verma 2019

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