An inkjet ink comprising water, colorant, and a dynamic surface active agent at an effective concentration such that the ink has a dynamic surface tension DST1 sec at 1 second universal surface age, a dynamic surface tension DST10 sec at 10 seconds universal surface age and a dynamic surface tension DST20 min at 20 minutes universal surface age, where DST20 min is less than each of DST1 sec and DST10 sec, and the difference between DST10 sec and DST20 min is greater than 9.2 mN/m at 21° C. or the difference between DST1 sec and DST20 min is greater than 15.5 mN/m at 21° C., and wherein the static surface tension of the ink is less than 50 mN/m. Maintaining a relatively large dynamic surface tension difference between the indicated time scales yields an optical density improvement in printed images.