How Erasers Are Made

How Erasers Work

Erasers work by combining two key properties that you also find in pastries: stickiness and crumbliness. (The first erasers were pieces of stale bread, so this bakery connection isn’t just a coincidence.)

Crucially, erasers, unlike pastries, aren’t sticky and crumbly all the time. When you rub the eraser on the paper, you create friction, which in turn generates heat, and that activates the stickiness and crumbliness.

The stickiness is for pulling the graphite pencil markings off the page. (Pencil cores haven’t been made of lead for centuries, although they are still best left unchewed.) The eraser is stickier than the paper, so the graphite says, “See ya!” and moves over to the eraser.

The crumbliness comes in because once you’ve got the graphite off the paper, you don’t want it hanging around on the eraser and causing smudges the next time you use it. Instead, the eraser is supposed to crumble as you rub, and those little pieces whisk away the graphite, leaving both your remaining eraser and your page clean, ready for your next mistake.

What Erasers Are Made Of

Bread! No, that was a long time ago, we’ve found some better materials since then. Although if you want to try printing your logo on bread and then using the bread to erase pencil markings, let us know whether it worked.

Unless you are buying promo erasers for artistes, the two types of eraser you’re most likely to encounter are made of synthetic rubber or plastic.

Synthetic Rubber Erasers

Erasers in the ends of pencils and those classic chunky pink erasers are made of synthetic rubber. (Did you know that shape is called a parallelepiped? That’s the 3D version of a parallelogram: Drop that fact next time you encounter an awkward silence.)

Erasers used to be made from real rubber – the rubber that comes out of trees – combined with some other stuff to make it more durable and flexible in a process called vulcanizing. (Vulcanizing was developed by Charles Goodyear, of tire fame, a complete lunatic. The name comes from Vulcan, the Roman god of fire, who, yes, also gave his name to the Vulcans in “Star Trek.”)

However, during the early 20th century, scientists developed synthetic rubber, which was better quality than real rubber, plus easier and cheaper to make. This was especially crucial during World War II, when moving raw materials on ships meant running the risk of being torpedoed.

Synthetic rubber erasers are usually made of either styrene-butadiene rubber or ethylene-propylene rubber, plus fillers like calcium carbonate (chalk) to get it to the right thickness; sulfur as part of vulcanization (yes we’re still doing that); and vegetable oil to soften it up and prevent damage to the paper.

Another change from the original rubber erasers is that the pink color used to come from pumice, which is sometimes still added to help scrape the pencil markings off the page. Most erasers no longer use pumice, but the pink coloring is added because people still expect erasers to be pink.

Plastic Erasers

And then plastic came along and threatened rubber’s domination in the eraser material category. Plastic erasers are usually made of polyvinyl chloride (PVC). You can find out more about plastics, including PVC, in this blog post. There has been debate about whether it is or isn’t the greatest blog post about plastics ever written, but it’s definitely my favorite.

PVC is almost as old as vulcanized rubber (it was invented in 1872) but it didn’t become actually useful until people added plasticizers to make it flexible. That happened in the 1920s, around the same time people were figuring out synthetic rubber. Plastic erasers contain the same fillers as synthetic rubber erasers (chalk and stuff), and the plasticizers also help make the plastic soft enough to spare the paper, without the need for vegetable oil.

Which Eraser Is Better?

Look, I’m not here to yuck your yum. Maybe you just can’t resist the classic pink eraser, or you can’t get enough of your plastic eraser. Use the eraser you love the most.

However, eraser experts – who are totally here to judge your eraser preferences – would point out that PVC erasers have the whole crumbling aspect of being an eraser down better than synthetic rubber erasers. Synthetic rubber erasers tend to turn to dust, making them harder to get off your page and leaving more graphite behind on your eraser. In contrast, PVC erasers create bigger crumbs, which means less graphite left on the eraser and easier cleanup.

Synthetic rubber erasers also have this pesky habit of drying out if you leave them in the sun (not outside, just on a desk.) This makes them more brittle, prone to crumble, and less effective.

How Erasers Are Made

This is the fun bit. Even more fun than when I told you how Vulcans got their name or explained why synthetic rubber erasers are pink. This bit has pictures, so it’s worth more words than all the rest of this article.

1. 

   1. Mix Ingredients Using Heat and Motion

   Synthetic erasers are mixed on giant rollers that look like a massive version of those hand-cranked pasta makers. PVC is mixed in a big vat with a pole in the middle to stir.

2. 

   2. Mold to Shape

   The material is shaped while it’s still warm and malleable. Synthetic rubber is cut into large squares. PVC is poured into a machine that pushes it onto a conveyor belt, shaping it into a long strip, or poured into an injection mold to make individual shapes.

3. 

   3. Only For Rubber: Vulcanize

   Add heat to activate the sulfur and accelerators. This process makes the synthetic rubber more durable and flexible: you can thank Charles Goodyear for figuring that out.

4. 

   4. Cool to Set

   As the rubber cools down, it hardens from viscous goop to soft solid. This happens inside the injection mold, if you’re using that.

5. 

   5. Cut to Shape

   Once the material has cooled, you can cut your long strips or big squares into smaller strips or squares.

6. 

   6. Add Design

   Erasers are usually pad printed with your logo: Find out how that works in this blog post about pad printing.

The Bottom Line

Since everyone makes mistakes, everyone needs an eraser. Now you know how we make them and the different kinds, you can get your promo erasers right every time.