Pigment dispersions

An ink, comprising:

• a pigment dispersion, including:
• from 5 wt % to 30 wt % of a pigment having an amide group;
• a styrene acrylic polymer having a weight average molecular weight from 1,000 Mw to 30,000 Mw and styrene acrylic polymer to pigment weight ratio from 1:1 to 1:10;
• a lactam co-solvent having a weight ratio to the pigment of from 10:1 to 1:10, wherein the lactam co-solvent is co-milled with the pigment and an at least 5 wt % portion of the lactam co-solvent is adsorbed on the pigment via van der waals interaction with the amide group;
• and
• water;
• and
• an ink vehicle admixed with the pigment dispersion to provide an ink having from 1 wt % to 8 wt % pigment.