Naked Science Forum

Non Life Sciences => Chemistry => Topic started by: chris on 06/04/2015 00:32:46

Title: How does a pencil eraser work?
Post by: chris on 06/04/2015 00:32:46

What is the process by which a rubber - or eraser - removes pencil from paper?

Title: Re: How does a pencil eraser work?
Post by: RD on 06/04/2015 02:36:21

The graphite preferentially sticks to the eraser, rather than the paper. Friction with the paper causes the eraser to shed its graphite-coated outer-surface, exposing clean, graphite-free eraser to continue the erasure.  Some hard erasers also erode the surface of the paper, removing some graphite in the process.

Blue-Tack can be used as a pencil eraser (http://en.wikipedia.org/wiki/Blu-Tack#Uses) : lifting the graphite off the page without damaging the paper ... http://en.wikipedia.org/wiki/Kneaded_eraser

Title: Re: How does a pencil eraser work?
Post by: chris on 10/04/2015 22:35:10

Why does the graphite "like" the rubber more than the paper?

Title: Re: How does a pencil eraser work?
Post by: evan_au on 10/04/2015 23:38:30

Graphite consists of many thin sheets (graphene) which are strongly bound within a sheet, but only weakly bound between sheets, so they easily slide over each other.

The eraser tears these stacks of graphene apart, reducing their thickness to invisibility, in a method somewhat similar to the sticky-tape method which won the Nobel Prize in Physics for 2010.

So the eraser does not need to attract the graphite more strongly than the paper.
The rubber only needs to attract the graphene more strongly than the graphene is attracted to graphene.

Title: Re: How does a pencil eraser work?
Post by: diethyl on 30/04/2015 06:42:42

Why it's difficult to remove the traces from ball-point pen?

Title: Re: How does a pencil eraser work?
Post by: evan_au on 30/04/2015 12:32:11

The ink of a ball-point pen soaks into the paper fibers.
To remove the ink, you must remove the surface fibers containing the ink, which changes the texture of the paper surface.