What is a fountain pen?
A modern fountain pen is one of the simplest machines known to man (next to the wheel, of course). It uses the opposing forces of capillary action and surface tension to force a fluid to flow through a small hole. There are usually no moving parts in a fountain pen – they just aren’t necessary. In science, this type of machine is called a “gravity pump”. It depends on gravity as well as capillary effect. However, fountain pens don’t only work right-side-up: they will also work upside down. Why? Again, capillary action. As long as ink is trapped in the feed, it will continue to be drawn along the ink channel toward the tip of the pen until the feed is empty. You may have to turn the pen nib-downward to fill the feed, however.
