Rollerball pens use ball point writing mechanisms with water-based liquid or gelled ink, as opposed to the oil-based viscous inks found in ballpoint pen. The characteristics of these less viscous inks, which tend to saturate more deeply and widely into the paper than other types of ink, give rollerball pens their distinctive writing qualities.

The rollerball pen was initially designed to combine the convenience of a ballpoint pen with the smooth "wet ink" effect of a fountain pen. Gels usually contain pigments, while liquid inks are limited to dyestuffs, as pigments will sink down in liquid ink sedimentation. It is the thickness and suspending power of gels that allows the use of pigments in gelled ink. Using pigments (the same pigments that are used in paint) yields a greater variety of brighter colors than is possible in liquid ink, so gel-based pens are available in a brighter and wider range of colors than liquid ink pens.

Images & content © Robert Altig Turnings 2007

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