When the first ballpoint pens appeared on the market in the early 20th century, nobody thought they would last -- they were so unreliable and prone to leaks and smears that no one would have thought that by the end of the century they would turn the fountain pen into a relic. The greatest challenge to developing the ballpoint pen was the composition of the ink. Only when that problem was solved could ballpoint pens take over the writing world.
Fountain and dipped pens have been in use since the beginning of writing, and despite such problems as smearing ink and the delicacy of the pen’s mechanism, they proved adequate for most applications.
The first ballpoint pen was invented by a leather manufacturer in 1888, who found that the fountain pen would not write on leather’s rough surface. This ballpoint was crude, but it had all the characteristics of future ballpoint pens: a small, rolling ball held in place by a socket, and a reservoir of ink that coated the ball as it rolled across the surface.
Biro's Ink Innovation
For the next 50 years, inventors struggled to make the ballpoint pen suitable for writing on paper. Early ballpoints used variations on fountain pen ink, which is thin and gravity-fed. In combination with the rolling ball, these inks would either clog or smudge.
Laszlo Biro, a Hungarian newspaper editor, unlocked the key to the modern ballpoint pen when he observed that the thick newspaper ink he used in his presses dried instantly and never smudged, unlike the thin ink used in his fountain pen. He formulated a thick, viscous ink, then refined the ballpoint to release the ink.
Ballpoint ink is specially formulated to be thick and fast-drying. Its viscosity is precisely controlled: it must be as thick as possible but still thin enough to flow down the barrel of the pen in response to gravity.
Inks consist of a pigment or dye, dissolved or suspended in a solvent. Pigments are tiny colored particles that are suspended in the solution; dyes are completely soluble in liquid. Ballpoint pen inks use dye because the tiny particles of undissolved pigment can clog the ball of the pen.
The solvent of most inks is water or oil. Ballpoint pen ink is usually oil-based to give it its thickness. Oil also is why ballpoint pen ink dries quickly and is permanent and water-fast.
Ballpoint pen ink is about 50 percent dye. Black ink gets its color from carbon black, a fine powder made from soot. Red ink is made from eosin. Several dyes are used to make blue ink, but the more common ones include substituted triphenylmethane dyes, copper phthalocyanine blue and crystal violet. Black and blue inks often contain iron sulfate, and gallic and tannic acids. These additives have been used since the Middle Ages to make ink more permanent.
The dyes and additives are dissolved in a solvent, often ethylene glycol or propylene glycol. Then synthetic polymers, often nitrocellulose-based, are added to help disperse the dye through the ink and adjust the viscosity and surface tension.
Finally, such additives as resins, preservatives and wetting agents can be added to adjust the final properties of the ink.