Roller ball pens or rollerball pens are pens which use ball point writing mechanisms with water-based liquid or gelled ink, as opposed to the oil-based viscous inks found in ballpoint pens. These less viscous inks, which tend to saturate more deeply and more widely into paper than other types of ink, give roller ball pens their distinctive writing qualities. The writing point is a tiny ball, usually 0.5 or 0.7 mm in diameter, that transfers the ink from the reservoir onto the paper as the pen moves.
A roller pen or simply roller is a type of pen using a gel or water-based ink created, unlike a conventional ball pen that uses a viscous and oily ink. The lower viscosity of these inks allows a better saturation of the paper, which gives the roller its writing qualities.
Gel inks usually contain pigments, unlike aqueous inks that contain dyes. Indeed, the aqueous inks are less dense than gelled inks, the pigments tend to flow there, by sedimentation. The use of pigments in gelled inks allows the creation of a wide variety of colors, including opaque pastel colors that can be applied to dark surfaces, or metallic or scintillating effects. In contrast tinted aqueous inks can not be applied to dark substrates because of the different reflective properties of pigments and dyes. The differences are all related to the lower viscosity of the inks employed, with notable differences between gelled inks and aqueous inks.
Rollerball pens were introduced in 1963 by the Japanese company Ohto. There are two main types of roller ball pens: liquid ink pens and gel ink pens. The ‘liquid-ink’ type uses an ink and ink supply system similar to a fountain pen, and they are designed to combine the convenience of a ballpoint pen with the smooth “wet ink” effect of a fountain pen.
Gel inks usually contain pigments, while liquid inks are limited to dyestuffs, as pigments will sink down in liquid ink (sedimentation). The thickness and suspending power of gels allows the use of pigments in gelled ink, which yields a greater variety of brighter colors than is possible in liquid ink. Gels also allow for the use of heavier pigments with metallic or glitter effects, or opaque pastel pigments that can be seen on dark surfaces.
Liquid ink roller ball pens flow extremely consistently and skip less than gel ink pens do. The lower viscosity of liquid ink increases the likelihood of consistent inking of the ball, whereas the higher viscosity of gel ink produces “skipping”, that is, occasional gaps in lines or letters.
In comparison to ballpoint pens,
The pressure to be applied to the roller to obtain a suitable writing is less than with a ballpoint pen, which makes it possible to hold the roller less firmly and thus to increase the comfort of writing over time.
Rollerblades have a greater choice of colors due to the wide variety of dyes and pigments available.
Water ink rollers slide on paper more evenly than ballpoint pens and leave fewer whites. Conversely, the risk of intermittent interruption of the ink flow is slightly greater with gel ink rollers.
Less pressure needs to be applied to the pen to have it write cleanly. This permits holding the pen with less stress on the hand, saving energy and improving comfort. This can also translate to quicker writing speeds. This is especially true of liquid ink pens.
The inks usually have a greater range of colors due to the wider choice of suitable water-soluble dyes and/or to the use of pigments. They tend to write more clearly than ballpoint pens do.
The risk of “burrs” is higher with an aqueous ink roller than with a ballpoint pen because the ink dries more slowly, like that of a fountain pen. The gel ink dries almost as fast as the ink of a ballpoint pen.
The aqueous ink is also more easily absorbed by the paper than the ballpoint pen ink and to a lesser extent than the gelled ink because of its lower viscosity. The aqueous ink being absorbed continuously by the paper, this increases the risk of stains in case of pause.
Rollers have a shorter shelf life than ballpoint pens, with the ink being absorbed in larger amounts by the paper. This is especially true for water ink rollers.
The tip of a roller will become clogged more easily than that of a ballpoint pen if it passes over undried liquid corrector (blanco). This can make a roller unusable.
Water-based roller ball ink is more likely to smudge than a ballpoint pen’s oil-based ink because water-based ink dries more slowly than its counterpart. Also if one writes in a notebook, closing it before the ink dries can stain the opposite page. This can also prove a problem for left-handed writers or users of right-to-left scripts. Gel ink dries much more rapidly than liquid-ink, making it much more, but not completely, resistant to smudging.
Roller ball pens with liquid-ink are more likely to “bleed” through the paper. Liquid ink is more readily absorbed into the paper due to its lower viscosity. This viscosity also causes problems when leaving the tip on the paper (to pause for a thought for example). The bleed-through effect is greatly increased as the ink is continually absorbed into the paper, creating a blotch. This does not affect gel-ink roller ball pens as much. This is one way through which the thickness of gel-ink gives it an advantage, in that it isn’t as prone to being absorbed. Though the bleed-through effect of a gel-ink roller ball is greater than that of a ballpoint, it is usually not too significant.
Roller ball pens generally run out of ink more quickly than ballpoints because roller balls use a greater amount of ink while writing. This is especially true of liquid-ink roller balls, due to gel ink having a low absorption rate as a result of its thickness. Neither lasts as long as a ballpoint.
Uncapped roller ball pens are more likely to leak ink when, for example, placed into a shirt pocket, but most pens include caps or other mechanisms to prevent this from happening.
A roller ball tip is more likely to clog and jam when writing over correction fluid that has not yet completely dried. This often renders the ink cartridge useless.