This article sets out to outline the different types of ink pens available to the modern consumer, as well as outline the historical development of writing instrument technology.

All ink pens operate, at some level, on the principle of capillary action. Capillary action is a description of how surface tension will draw liquids up a tube or slot. In the case of a pen, capillary action either draws ink down the ink cartridge or holds it in the pen in case of older designs.

The main historical types of pens are dip, reed, and quills. Dip pens have a metal tip, or nib, that holds ink for writing. The nib has a small slot running through its middle that draws up ink via capillary action. The small ink capacity of the nib requires that the pen is dipped in the ink pot frequently during writing. A reed pen and a quill operate on basically the same capillary principle – the hollow tube inside the pen draws ink inside it and is stored for writing. Quills are made from sharpened feathers and reed pens are made from a reed or small diameter bamboo.

Three main types of pens are available today. Most common is the ballpoint pen. As common in all modern pens ink is contained within the pen body in a cartridge or tube. The tip of a ballpoint pen contains a small metal ball that is free to roll around. As the ball is rolled across the paper it deposits ink, creating a line. The ink of ballpoint pens is thick and oily in composition, which gives resistance as the pen tip is moved across the paper. A roller ball pen is identical to a ballpoint pen except for the composition of its ink. The ink of a roller ball pen is water based and thin, which makes it soak into paper more freely. These results in a smoother feel to the pen, but can make lettering sloppy if a stable writing surface is not present. The third type of modern pen is the fountain pen. It is a hybrid between a dip pen and a modern pen with a reservoir of ink. Ink is either contained in a replaceable cartridge or a re-fellable reservoir. The ink is draw via capillary action from the reservoir through a passage to a nib. Some models have interchangeable nibs to customize the weight of the line drawn. Fountain pens are re-usable and are made in a range of materials and qualities with the more expensive models costing thousands of dollars.

Fountain pens also make excellent gifts for professionals, graduates, and avid letter-writers. Most merchants offer custom engraving and sumptuous display boxes.