10 Things You Probably Did Not Know About Eraser Technology

Fact #1: Before rubber came along, people undid their mistakes using wadded-up bread.

John Russell / AP

It's true, as Arthur C. Clarke said, that the most advanced technologies are indistinguishable from magic. It's not true, however, that the world's most magical technologies are all related to computers. What could be more magic, after all, than the eraser—the little wad of rubber that undoes your mistakes and changes, mark by tiny little pencil mark, human history?

Erasers as we know them today are a relatively modern invention. But erasers as a general category are age-old. The ancient Greeks and Romans relied on palimpsests and smoothable wax tablets to ensure erasability. Those gave way, eventually, to White-Out and Photoshop's "magic eraser" tool and, of course, the ultimate undoer of deeds: the delete key. But erasers are far from obsolescencejust as writing itself is far from obsolescence. Below, 10 things to know about erasers.

1. The original erasers were bread. Moist bread.
Until the 1770s, humanity's preferred way of erasing errant graphite marks relied on bread that had been de-crusted, moistened and balled up. While these erasers were cheap and plentiful, they had a distinct disadvantage: They were, you know, made of bread. They were susceptible, like all bread, to mold and rot. Talk about a kneaded eraser.

2. The same guy who discovered oxygen helped to invent erasers.
In 1770, the natural philosopher and theologian Joseph Priestley—discoverer of oxygen and, with it, the carbonated liquid we now know as soda water—described "a substance excellently adapted to the purpose of wiping from paper the mark of black lead pencil." The substance was rubber.

3. Erasers were invented by accident.
Though Joseph Priestly may have discovered rubber's erasing properties, it's the British engineer Edward Nairne who is generally credited with developing and marketing the first rubber eraser in Europe. And Nairne claimed to have come upon his invention accidentally: He inadvertently picked up a piece of rubber instead of breadcrumbs, he said, thereby realizing rubber's erasing properties.

4. "Rubber" actually gets its name from erasers.
It was Priestley who is generally credited for naming rubber. The erasing "substance" he described in 1770—initially referred to as "India gum"—required, he remarked, rubbing action on the part of the user. Thus, yep, a "rubber." The name ended up generally applying to erasers' construction material rather than erasers themselves, especially after Charles Goodyear figured out how to vulcanize the stuff in the mid-1800s. In Britain, erasers themselves are still often called "rubbers." (Which may lead to some confusion, maybe.)

5. Erasers don't just work manually; they work chemically.
Pencils work because, when they are put to paper, their graphite mingles with the fiber particles that comprise the paper. And erasers work, in turn, because the polymers that make them up are stickier than the particles of paper—so graphite particles end up getting stuck to the eraser instead. They're almost like sticky magnets.

Thumbnail image for 800px-Office-pink-erasers.jpg
Malaysian-manufactured Pink Pearl erasers (Wikimedia Commons).

6. Pencils with built-in erasers on the tops are a largely American phenomenon.
Most pencils sold in Europe are eraser-less. Read into that cultural difference what you will.

7. Many erasers contain volcanic ash.
Those ubiquitous pink erasers, in particular—the pencil-toppers and Pink Pearls of the world—make use of pulverized pumice to add abrasiveness. And pumice is, of course, volcanic ash.

8. The little erasers on pencil ends are known as "plugs."
Yep. And those small bands of metal that contain the plugs are called "ferrules."

9. Many of today's most high-tech erasers are made of vinyl.
While the pink erasers you find on pencils are made of synthetic rubber, an increasing number of erasers are made of vinyl. Vinyl's durability and flexibility give erasers made of it "minimal crumbling," and offer, overall, "first-class erasing performance." Plus, obviously, the sound quality is richer with vinyl.

10. There are such things as electric erasers.
Seriously. These erasers supposedly offer "a smooth erasure with a minimum of paper trauma."