You’re using pencil, fast and furious, to scribble notes when you make a mistake. Maybe after all these years you’re still mixing up b’s and d’s. No matter, because on the other end of your writing implement sits its perfect counterbalance, that predecessor to the delete key: the eraser. Only when you flip over your pencil and rub, the eraser doesn’t do its job. In fact, it makes it worse—smearing black graphene all over and perhaps even ripping the page.

As another year of school supply shopping season has come and gone, it’s time to finally ask ourselves the question at the center of the aforementioned, all-too-common scenario: Why are most erasers awful at erasing?

Finding a pencil with an honest-to-goodness, functioning eraser is much harder than it should be, and even separate erasers sold on their own often do a middling job. The meme “you had one job!” seems apt here, until you consider that most examples in the “you had one job!” genre—billboards put up incorrectly, railings slanting in the wrong direction—are onetime mistakes rather than systemic failures. According to Andy Welfle, who runs a wooden pencil blog called Woodclinched and co-hosts the Erasable podcast on the same topic (and has lately been partial to a Czechoslovakian eraser), “pencils that you can just buy at Office Depot, or Staples, or Walmart, something like that, a lot of them do have really terrible erasers. A lot of them are just kind of a plain cheapish rubber.”

Erasers were invented in 1770 by an engineer named Edward Nairne. Nairne used rubber from trees, and his magical device was so impressive that the theologan Joseph Priestley mentioned it in a footnote in his book A Familiar Introduction to the Theory and Practice of Perspective: "I have seen a substance excellently adapted to the purpose of wiping from paper the mark of black-lead-pencil,” he wrote. Since then, as material engineering has improved, erasers have become more high-tech.

But even among eraserheads, the exact composition of today’s erasers is a bit of a mystery. Precise breakdowns of materials tend to be guarded as company secrets. Rigoberto Advincula, a professor at Case Western Reserve University who has consulted in the pencil and eraser industry, said that erasers are usually made of some combination of rubber and plastic components. Natural rubbers—made from the stuff that comes from rubber trees—have good erasing properties. Thermoplastics, a type of polymer that can be hardened or softened depending on heat, are easier to shape. A host of additives, like additional particles and aromatic agents, can tweak the mixture further, as can the compounding process. The erasers we see in stores are almost always some proprietary combination of all three.

Natural rubbers make the best erasers, because their innate abrasive qualities help them remove material from paper with aplomb, Advincula said. The cheaper plastics that have been embraced by eraser manufacturers—including PVC, which raises environmental concerns too—are the ones that cause problems, because, well, you get what you pay for.

In the end, cheaper raw materials like bottom-of-the-line thermoplastics and synthetic rubbers beget cheaper, and worse, erasers. Charles Berolzheimer, CEO of CalCedar, a supplier of wooden slats for pencils, attributed the decline in eraser quality to globalization. As companies focused on keeping prices down, they moved their manufacturing to Asia and sought out cheaper materials. The cheaper the pencil, the cheaper the eraser, so upgrading your pencil (or upping your separate eraser budget) might be one way to guarantee improvement.

You might be inclined to try and find vintage erasers, from the good old days before polymer contamination. But that wouldn’t work either. While a pencil from 1770 would, after a rejuvenating sharpening, still work, an eraser from that same time would not. Johnny Gamber, who co-hosts the Erasable podcast with Welfle and keeps a blog called Pencil Revolution (and who likes either the Faber-Castell white plastic eraser or the Staedtler Mars white plastic eraser), pointed out that, “erasers age, pencils don’t. You can use a hundred-year-old pencil and sharpen it and it will work just fine. You can’t really stock up on erasers because they dry out.” (This idea inspired the slogan on a t-shirt the Erasable podcast sells: “Pencil is forever.”) Advincula explained: “Over time, some of the rubber properties can be lost because of oxidation or chemical degradation. Some of the plastic can also soften or even harden because of different environmental conditions.” In short, exposure to air and light is doing your erasers no favors.

“Presumably if you had a pencil with an eraser from a hundred years ago and it had been hermetically sealed, it might still work,” added Henry Petroski, an engineering professor at Duke and author of The Pencil: A History of Design and Circumstance.

Sadly, there is a distinct lack of hermetically sealed pencil cases available in the current marketplace. Perhaps the solution is to seek out pencils with erasers made of different materials. But it turns out that erasers attached to pencils may simply never be ideal. “The eraser-tipped pencil is more of a U.S.-based phenomenon,” Berolzheimer told me. “If you look at graphite pencils in other countries … they don’t have erasers, and people are used to using a handheld eraser. Usually a handheld eraser tends to perform better, just because it’s larger, has a broader surface, has a little more control.” Erasers made purely to erase are more likely to do that job well, and more surface area also reduces the eraser’s chances of drying out.

Gamber has noticed some improvement on the materials front too: “The materials people are using for erasers is getting a lot better,” he said. No longer do rubber erasers dry out quite as fast. “Even the Pink Pearl, which is one of my favorite erasers even though it doesn’t really work that well, they’ve made it softer. They used to sort of petrify. It was disgusting.”

Of course, it’s only for the last 250 years or so that pencil-pushers have enjoyed the luxury of erasers. Petroski, the pencil historian, said that before Nairne introduced his rubber eraser, people used bread to erase. “I did try it, a long time ago,” he said. “It depends on the bread, of course.” As with modern erasers, “there’s good bread and bad bread as far as erasing pencil marks.” Meaning that your standard loaf may just be superior to that dried-up #2 topper.