Science in everyday life: fountain pen & Co

Pen & Co

Modern writing instruments seem to have little in common with the slotted bamboo canes of the Egyptians or the quills of medieval monks. And yet they work on the same basic principle: capillary forces draw ink or paste onto the paper.

Of course: fountain pens, ballpoint pens and rollerball pens are much easier to use than the goose quill, because a supply of ink saves you from dipping into the barrel and precise mechanical control systems ensure a smudge-free flow of ink.

A slotted metal spring closes the ink channel on the fountain pen until it is slightly bent upwards by the writing pressure. In the gap between spring and channel and in the now slightly open slot, capillary forces pull the liquid towards the paper. Without further measures, however, a negative pressure would build up in the container and disrupt the even flow. Blots, leaks or a lack of ink were the norm until the American insurance agent Lewis E. Waterman developed a ventilation system for the tank in 1884: Used ink is replaced with air in a controlled manner.

The development of the fountain pen did not end with the pressure equalization. Fine lamellar structures, the so-called compensation chambers, temporarily store ink when temperature and air pressure fluctuations force liquid out of the reservoir. This buffering also aids in smooth ink flow. Ballpoint pens and rollerball pens replace the nib of the fountain pen with a metal ball, usually made of hard-wearing tungsten carbide, which can rotate freely in a socket. The fine gap between the two provides the capillary forces necessary for writing. While the refill of a ballpoint pen contains paste containing dye (and large-capacity refills have a grease seal at the rear end), a ballpoint roller is ink.

Fiber pens and ballpoint pens also use ink. It is pulled out of the container of the refill via a wick and the paper is also released via a wick in the case of the fiber pen. The ink can be stored "free" or bound in a tampon. The latter prevents any leakage, but the flow of ink from these refills becomes weaker and weaker over time.

New developments are usually based on one of these principles, use modern processes to optimize the mechanics or ergonomic handling, rely on new materials and an attractive design. While a plastic ballpoint pen can be bought in the supermarket for a few euros, a prestigious item from the Heidelberg company Lamy, for example, can easily cost a few hundred. And that's also the problem of the industry in Europe: They can compete with cheaply produced pens in Asia with quality, but the profit margins are shrinking. In one of the most important sales markets, school supplies, it has long been hard to score points with quality work when it comes to writing implements - schoolchildren and parents now have other products in mind.

Did you know?

The patent for the ballpoint pen concept was granted to the Hungarian Laszló Biró in 1938. In 1944 he delivered 30,000 pieces to the British Air Force because his invention was supposed to be less sensitive to fluctuations in air pressure than fountain pens. From 1945 other American companies also entered the market, but it was precision mechanics and watchmakers in the Black Forest who first succeeded in manufacturing ink channels and ball mounts with the necessary precision.

The air in the ink reservoir is under atmospheric pressure when boarding an aircraft, but the cabin pressure is reduced at high altitude – without special equipment, stains would result. However, it is still recommended to fill up a fountain pen as much as possible before departure.

• Ink pens have a ten times greater flow of writing medium than ballpoint pens. Your typeface is therefore more attractive, but the refill only reaches about 1000 to 1500 meters, with a ballpoint pen it is 5000 to 10,000 meters depending on the tip.
• Already in ancient times, mixtures of iron s alts and tannic acid were used for writing because they left deep black marks. The raw material for the tannic acid was obtained from galls, growths on the leaves and branches of oak trees. In the Middle Ages, this iron gall ink became more and more popular and was further developed into a ready-made ink by the Dresden perfumery manufacturer August Leonardie. Today, the alternatives are aqueous solutions of aniline dyes, preservatives and other additives.

• Gold and silver are attractive lettering colors for greeting cards, for example, but the heavy metal pigments settle quickly in aqueous inks. They are therefore introduced into highly viscous gels, which only become liquid through the shearing movement of the ball roller.

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