What is a ball point pen?
At the heart of a ball-point pen, is a small ball which seals the chamber containing a viscous ink system. As the operator moves the pen across the surface the rotation of the ball transfer ink from the sealed chamber to the writing surface. The ball has two key functions which are to seal the ink chamber and to transfer the ink to the writing surface. The ink is fed by gravity to the upper surface of the ball. The image shows the main components for a particular pen. The centre item is the ink reservoir, the brass pen tip on the left is inserted in the ink reservoir and the whole assembly is inserted in the pen holder on the right. We have used a scanning electron microscope to look at the metal ball in the pen tip more closely as shown in the image to the right. At this scale or magnification the ball looks very smooth. However, we can zoom in to a much higher magnification and see that the surface of the ball is far from smooth. This surface roughness will play a part in the transpo
