We’ve all seen ballpoint pens that still have plenty of ink showing through the plastic barrel, but nontheless stop working. Who hasn’t almost thrown a non-working pen through a closed window out of frustration? Sometimes, after scribbling on something for a few minutes, the pen starts writing again. Other times, you can scribble until the paper tears, but the damned thing just will not write.
Question: why do these pens stop writing? How can I get a pen to start writing again when it obviously still has plenty of ink in it?
A ball point has a literal ball for a point. As it moves across the writing surface, the friction rolls the ball* which constantly runs a surface through the ink above it and onto the surface below. If the pen is left unused for a long enough time, the ink that is exposed to the air in the minute space between the ball and the shaft dries and hardens. If it has been a short while since the pen was used, vigorous rubbing of the ball against a paper may break out that dried ink and allow the ink behaind it to run freely, again. If it has been too long, the ball will be lock in place. If has been a really long time, the visible ink in the cartridge may, itself, be dried out and not capable of being drawn onto the page.
*The friction aspect of the device also explains why ball points do not write across grease stains: there is no friction to roll the ball to draw the ink.
Heat often works with a normal ballpoint pen that has stopped working. I just use a lighter though it is easy to overdue it and melt the tip which can result in too much ink coming out or ruining the pen altogether. In my experience it works better then just scribbling.
somewhat of a different question, but how come simply retracting the ball-point tip into the pen (clicking the button on the end) prevents the ink from drying out? It is still exposed to air. Same thing with putting a cap on the pen. How does that prevent the ink on the tip of the ball from drying out?
If you look at the relatively large opening and short retract distance in a retractable pen, I doubt that the air stagnates very much. Also, compare this to non-retractable pens with caps that often have holes in them (so as not to produce a choking hazard).
I suspect the real reason for the retraction feature (or hole-y cap) is simply to keep ink off your shirt pocket.