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Author Topic: erasers for pencil and pen ink...how do they work?  (Read 5696 times)

Offline neilep

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hello, I'm Neil...nice to meet you,

I remember a few years ago..(well probably about twenty now !!)..that erasers were avaialable for pen ink too....In fact I think they were merely abrasive and literally just scraped the paper away...but if I'm wrong, can a passing eraser expert please answer how erasers work, not just for pen but also for pencil.....for our american chums, we also call erasers 'rubbers' over here...but I purposely did not use the word 'rubbers' because isn't that american slang for condoms ?..........DOH !!

Your perfectly spelled-without-correction answers would be most appreciated

Thanks

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Offline Ultima

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Re: erasers for pencil and pen ink...how do they work?
« Reply #1 on: 28/10/2004 22:05:59 »
What about those putty rubbers (erasers) they just lift the ink/lead off of the page?

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Offline tweener

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Re: erasers for pencil and pen ink...how do they work?
« Reply #2 on: 28/10/2004 23:19:09 »
I think they were a special ink, because the eraser would not erase regular pen marks without really scrubbing and taking out most of the paper.  Come to think of it, I saw some eraseable pens the other day in Wal-Mart, so I guess they're still alive.

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Online chris

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Re: erasers for pencil and pen ink...how do they work?
« Reply #3 on: 29/10/2004 08:49:09 »
Under a microscope paper resembles a lattice of cross-linked cellulose fibres. When you write on paper with a pencil the graphite readily fragments (because it is soft and crumbly) into small pieces which become lodged in the gaps in the lattice.

When you 'erase' pencil from paper, the 'rubber'  doesn't remove any paper - it merely plucks out the graphite particles which are sticking out of the paper meshwork. The situation is rather like shaking some flour on a black coat - you get a white mark where the flour has stuck to the surface of the coat, but a stiff brush or some sellotape will readily remove the flour again.

But ink is different. Unlike graphite, it doesn't exist as small particles which lodge in the paper surface - the dyes are much smaller and penetrate much further into the paper surface. To remove the dye you must physically remove the stained paper fibres. This can only be achieved with the help of an abrasive which 'sands down' the paper surface to a level below which the ink has penetrated. In some cheap papers (which are highly porous so the ink often goes right through) it may therefore not be possible to erase what you have written. Returning to the garment analogy, above, ink on paper is rather like pouring red wine on your favourite top or carpet - the dye particles are carried deep into the pile by the liquid and are extremely difficult to remove entirely.

Chris

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Offline neilep

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Re: erasers for pencil and pen ink...how do they work?
« Reply #4 on: 29/10/2004 19:54:10 »
Brilliant Chris....thanks.......and thanks to John and Matt too.

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Offline Danny

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Re: erasers for pencil and pen ink...how do they work?
« Reply #5 on: 01/11/2004 21:25:34 »
I find that very interesting, but I was still left wondering how the erasable ink pens worked.  Did they use a special kind of ink that wasn't as thick/dense perhaps and therefore didn't stain as many of the fibers.. or as deep?

Fun stuff.

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« Last Edit: 01/11/2004 21:27:33 by Danny »
 

Offline Ultima

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Re: erasers for pencil and pen ink...how do they work?
« Reply #6 on: 01/11/2004 23:29:35 »
Isn't that all chemical, to do with solvents and substrates 'n such things...

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Online chris

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Re: erasers for pencil and pen ink...how do they work?
« Reply #7 on: 02/11/2004 08:36:19 »
hi Danny, welcome to The Naked Scientists forum

You might be right, i don't know to be honest. If the ink is too runny then it penetrates too deeply into the paper and no amount of rubbing (short of rubbing a hole in the sheet) will remove it. If the ink is too viscid then it won't write nicely, and the pen would probably leave blobs which would smudge badly when you tried to rub out what you'd written. I suspect they went for an ink that wasn't too wet and tended to be laid down quite thinly.

You'll probably have noticed that I've resorted to the politician's technique of hedging my bets but, unlike a politician, I'll admit that I don't know the precise answer !

Chris

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Re: erasers for pencil and pen ink...how do they work?
« Reply #7 on: 02/11/2004 08:36:19 »

 

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