Why does an eraser work on pencil but not on pen?

[jobyts]

How does an eraser (rubber, for non-US) work? Any why it works only for pencil(or graphite) , not for pen?

 

[olgranpappy]

How does an eraser (rubber, for non-US) work? Any why it works only for pencil(or graphite) , not for pen?

the eraser rubs the graphite off the paper. graphite is a solid and sits on top of the paper (in a thin layer). that's why you can rub it off without destroying the paper underneath.

You can't rub off ink, because it dyes the paper--i.e., gets below the surface of the paper.

 

[LURCH]

And rubber is used for the same reason it is used in bicycle and automobile tires; because it has good traction. It "grips" the graphite just like tires grip the road.