Abstract: An electrocoagulation printing ink consisting essentially of a liquid colloidal dispersion containing an electrolytically coagulable colloid, a dispersing medium, a soluble electrolyte and a coloring agent, is improved by selecting as the colloid an anionic copolymer of acrylamide and acrylic acid having a weight average molecular weight of about 200,000 to about 400,000 and containing about 8 to about 15 weight % of carboxyl groups. The ink is free of surfactant associated with the copolymer. Such an ink is capable of forming dots of coagulated colloid which are resistant to abrasion, without producing undesirable background on the electrocoagulation printed images.