Question: How Do Pencil Erasers Work?
Roman scribes wrote on papyrus with a thin rod made of lead, called a stylus. Lead is a soft metal, so the stylus left a light, legible mark. In 1564 a large graphite deposit was discovered in England. Graphite leaves a darker mark than lead, plus it's non-toxic. Pencils began to be used, similar to the stylus, except with a wrapping to keep the user's hands clean. When you erase a pencil mark, it's graphite (carbon) you are removing, not lead.
Answer: What Are Erasers?
An eraser, called a rubber in some places, is an item used to remove the marks left by pencils and some types of pens. Modern erasers come in all colors, and may be made of rubber, vinyl, plastic, gum, or similar materials.
A Little Eraser History
Before the eraser was invented, you could use a rolled up piece of white bread (crusts cut off) to remove pencil marks (some artists still use bread to lighten charcoal or pastel marks).
Edward Naime, an English engineer, is credited with the invention of the eraser (1770). The story goes that he picked up a piece of rubber rather than the usual wad of bread and discovered its properties. Naime began selling rubber erasers, the first practical application of the substance, which gets its name from its ability to rub out pencil marks.
Rubber, like bread, was perishable and would go bad over time. Charles Goodyear's invention of the process of vulcanization (1839) led to widespread use of rubber. Erasers became commonplace.
In 1858, Hymen Lipman received a patent for attaching erasers to the ends of pencils, though the patent was later invalidated since it combined two products rather than invented a new one.
How Do Erasers Work?
Erasers pick up graphite particles, thus removing them from the surface of the paper. Basically, the molecules in erasers are 'stickier' than the paper, so when the eraser is rubbed onto the pencil mark, the graphite sticks to the eraser preferentially over the paper. Some erasers damage the top layer of the paper and remove it as well. Erasers attached to pencils absorb the graphite particles and leave a residue which needs to be brushed away. This type of eraser can remove the surface of the paper. Soft vinyl erasers are softer than the erasers attached to pencils, but are otherwise similar.
Art gum erasers are made of soft, coarse rubber and are used to remove large areas of pencil marks without damaging paper. These erasers leave a lot of residue behind.
Kneaded erasers resemble putty. These pliable erasers absorb graphite and charcoal without wearing away. Kneaded erasers may stick to the paper if they are too warm. They eventually pick up enough graphite or charcoal that they leave marks rather than pick them up, and need to be replaced.