ElI5: Why a pen sometimes refuses to write on a specific part of the paper but works perfectly fine everywhere else?
In: Other
A standard ball point pen requires friction. Initially there is only ink on the part of the ball that is inside the pen. Friction between the paper and the ball causes the ball to roll which brings the inked part of the ball to the paper (and inks more of the ball). When your pen isn’t working it means the ball isn’t rolling or the pen is out of ink.
Ball point pens work on paper because the surface of the paper is rough enough (at the microscopic level) to cause friction with the ball. Unfortunately, when a pen fails to write, your attempt to write presses down on the paper and often smooths the surface of the paper. This is why it often works better to try writing/scribbling on another section of paper (where it is still rough)
A pen might not initially write because the ink has dried in the “joint”. The friction between the ball and paper might not be enough to break the friction of resistance. Scribbling to get the pen working again works because you are applying a larger force to break up the dried ink.
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