Patents for ballpoint pens go back to the late 1800s, but it took half a century to develop good, fast-drying inks. Bic, Pilot, and other makers jealously guard their formulas, but to get that classic ...

Dye can’t stick to paper on its own—it needs surfactants like alkyl alkanolamide to help lower the surface tension so it can sink into that Post-it note before the ink dries. No one wants ink gunking ...