Pencils, Rubbers et al

Why does a rubber rub out pencil?

People are so nasty and horrible these days that if you ask a perfectly reasonable question they’ll say, ‘why don’t you google it, asshole.’ (It is possible to make these people look stupid by asking a rhetorical question…)

Back in the day, when I were a lad, I spotted a gap during a chemistry lesson, raised my hand and asked: “Why does a rubber rub out pencil?”

The class erupted in hysterics and I didn’t get a straight answer from the teacher. Later I asked my mate Paul Reid why everyone laughed. “Because only you would think of asking a question like that.”

Nearly four decades later I still don’t understand the physics of pencil erasers, so if anyone knows (serious answers only, no speculation) do leave a comment.

It’s not the only trivial bit of science that baffles me. Inkjet printers. We all take them for granted, hate them when they go wrong, and we know they’re designed to waste ink and therefore waste our money. But have you ever wondered how incredible they are from a technological point of view?

They can deposit a microscopic blob of ink anywhere on a sheet of paper no matter how big. This from a mechanical object. It’s not like a computer screen using algorithms and formulas to calculate which screen pixel to electrify. Printers have to move bits and pieces backwards and forwards, accurately, every time until the cyan cartridge runs out.

We don’t think about brilliance when the brilliance has become the everyday. What we take for granted seems simple, but it seldom is. Live events on television should astound you if you took a moment to think about what’s going on. All those tiny people running around a football pitch in Nice are not actors, it’s not a recording or a computer simulation, they really are there, thousands of miles away kicking a ball nanoseconds before you see it happen.

The technology, the speed of light broadcasting of an electronic signal is related to mobile phone technology. Take a look at that small oblong of plastic. Press the right button and some invisible connection is made to a mast somewhere, miles away. And the invisible connection travels through walls, through people’s heads, that passing bus is no obstacle. Everything between the phone and the mast is a conduit for the signal: electrons in the baby’s pram, the dog’s tail, the back fence, the cake display in Galloways, all vibrating and jumping to the next electron level to carry that mobile signal. No wonder everyone’s going mad with all the electromagnetic stimulation we’re bombarded with every day.

Hundred ton planes flying, thousand ton ships floating. It’s simple physics say the egg heads, but simple is still extraordinary.

I suppose if Aristotle had jumped out of his bath shouting eureka ten minutes earlier we might have had mobile phones forty years earlier and then I could have used mine to find out why rubbers rub out pencil. There’s nothing on the internet. Not even on google.


30 thoughts on “Pencils, Rubbers et al

  1. This is all very profound, Chris. You might think I didn’t comment before now because I was off doing non-internet things, or teaching dachshunds how to look taller. But it’s actually because I’ve been musing on the profundity for weeks now. I’m quite hungry now too.

    Liked by 1 person

  2. I think your experiences with childhood curiosity are indicative of the individual who thinks more, feels more, and unfortunately, is exposed to social risk and derision more often than the average person. Sometimes I’ve felt like that. Maybe that’s why we so often have good conversations via these blog creations of ours.

    For the record, I don’t know exactly how an eraser works, though I have theories about graphite and friction and stuff.

    Liked by 1 person

    1. I’d go with the answer below; about rubber being a fluid or something.

      I think being slightly detached does give you a different perspective on life and puts you at a distance where you can see people looking back at you. (Where I work, I’ve been told, in a nice way, that I’m on the verge of replacing the oddball who is retiring. I quite like that idea.)

      And I’ve just been mouthing off on your blog. I finally got to see a few films that you reviewed. There were two agreements and one digression. There need to be more in-depth blogs like yours.


  3. I actually saw a post about a teen who wrote something with a pencil on a paper and she made a typo, and when asked why she didn’t correct it, she said, “You can’t auto-correct when you write by hand.” And I was all like, “Sweetie that’s called using an eraser.”

    Liked by 1 person

  4. I was going to raise the problem of the ink rubber failing in its allotted task and gouging off a layer of paper instead, but I see it’s been dealt with quite adequately in the comments. But what I really want to know, in this high-tech world, is why nobody ever developed a pencil sharpener that didn’t snap the lead off one nanosecond before the point reached perfection?
    Mr Angry

    Liked by 1 person

  5. Well I gotta say it! I had no idea how erasers worked either! Always took it for granted. :-/ So, thank you Opening Sentence for a great post and thank you Woebegone but Hopeful for the answer! 🙂

    Liked by 1 person

  6. Good post, technology is astounding. I still marvel at those ‘mechanical computers’ that were in use during WWII.
    Rubbing out pencil marks is interesting because of the dynamics. The rubber being a ‘fluid’ and porous substance is able to pick up the small graphite parts which make up the pencil mark; the action of moving the rubber over the area causes the whole mark to be absorbed (and causing bits of rubber to fly off all over the place). The ink eraser design for the removal of old fashioned liquid ink was always a puzzle to me as, it’s only success seemed to be to make a hole in the paper! (An action never appreciated by teachers, as if the design flaw was your fault!)
    The trouble is about asking questions is that folk hate to be placed in a situation where they are seen not to have an answer. (Which is why I guess politicians are disposed to shout and wave their arms about)

    Liked by 2 people

    1. Don’t know why my chemistry teacher couldn’t have told me that. He obviously didn’t know. The ink rubbers were the opposite of everything my post is about: a technology that never worked. If you did manage to rub out the ink, the paper was left so rough any new writing became unintelligable.

      Liked by 1 person

    2. And here I thought those shameful holes left by the ink side of the eraser (which was blue, while the pencil side was pink) were my fault, that I never managed to use the right technique. It’s good to hear they didn’t work for others as well.

      Liked by 2 people

      1. No, rest easy Audrey, I never met anyone who could use the ink eraser for the intended purpose.
        (Now cutting off and used as a missile in a classroom, that was a different matter!)

        Liked by 2 people

              1. Holes in erasers were an art form (as were holes in desks)
                And who ever used dividers for the true purpose?
                As far as I can recall they were either hurled as spears, or with both points appearing betwixt the middle finger as a weapon of close combat.

                Liked by 1 person

      2. Blue and pink rubbers; I remember the colour scheme too.

        You don’t see them in the shops now. Maybe because people don’t write everything with pens anymore. Someone should write an app that mimics an ink eraser, and leaves a small hole in a document when you correct a spelling.

        Liked by 1 person

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