A pen is a tool used for writing or drawing with a colored fluid, such as ink. A ballpoint pen is a pen that uses a small rotating ball made of brass, steel or tungsten carbide to disperse ink as you write. It is very different than its pen predecessors -- the reed pen, quill pen, metal nib pen, and fountain pen (see A Brief History of Writing Instruments for details).
All of the pens that preceded the ballpoint used a watery, dark India ink that fed through the pen using capillary action. The problems with this technology are well-known. For example:
- The ink can flow unevenly.
- The ink is slow to dry. The ink is exposed to the air while it is flowing through the pen, so it cannot dry quickly or it would clog the pen.
- When it does accidentally dry in the pen, the ink gums the whole thing up and requires meticulous cleaning.
When you add to this list the fact that fountain pens tend to flood when you fly on an airplane with them, you can see that all pens up until World War II presented some significant problems for their users -- the world awaited a better solution.