Roller ball pens utilize water-based or gel inks. They were originally designed to give the "wet ink" effect of an old style fountain pen. Ballpoint pens use oil-based ink, which tends to soak more deeply into the paper. As a rule, roller ball pens write more boldly and require less pressure against the paper. However, the ink from roller ball pens takes a few moments to dry (unlike ballpoint ink) and can easily smear.
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