Set of reaction liquid and ink, and image forming method

摘要

Provided is a set of a reaction liquid that has a buffering action against pH change and exhibits a pH of 3.5 or more and 5.5 or less, and an ink that has a higher pH than the reaction liquid. The ink comprises a pigment to a surface of a pigment particle of which a basic group that forms a cation form at the pH of the reaction liquid is bonded. The pigment does not have an acidic group having a pKa equal to or less than the pH of the reaction liquid. The pigment is dispersed by a water-soluble polymer that has an acidic group having a pKa equal to or more than the pH of the reaction liquid and equal to or less than the pH of the ink.