How Ball Point Pens Work

Components

A ballpoint pen is a simple, common and effective writing tool. A standard ballpoint pen consists of an internal reservoir filled with a viscous, quick-drying ink, a small metal sphere made from brass, steel or tungsten carbide and a socket. The metal sphere or "ball" rests firmly in the socket. Ballpoint pens have either a cap to protect the writing tip or a spring mechanism to retract the tip into the pen when not in use. Ballpoint pens are primarily made out of plastic with some metal parts.

Function

The ball rests in the socket tight enough to protect the ink in the reservoir, but loose enough so it will turn once pressure is applied. The back of the ball is exposed to the ink in the reservoir so it will pick up the ink. As you firmly press the pen to paper, the rotating ball transfers the ink from the reservoir to the writing surface with the help of gravity. Because the ink is viscous, standard ballpoint pens require firm downward pressure to get the ink flowing and cannot write effectively on materials like glass, wet surfaces or upside-down. Variations such as roller ball pens overcome these drawbacks by combining ballpoint pen technology with more liquid ink and the ink-flow systems of fountain pens.

Advantages

Before the innovation of the ballpoint pen, fountain pens relied on capillary action -- how molecules move liquid move across a solid object -- to draw the ink from the reservoir to the tip. There were several possible problems with these pens, including uneven ink flow, ink drying in the reservoir, slow-drying ink and leakage. The standard ballpoint pen solves all of these problems.

References

• eNotes
• Encyclopedia.com
• Quido