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.

Abstract: The shelf-life of an electrocoagulation printing ink consisting essentially of a liquid colloidal dispersion containing an electrolytically coagulable colloid, a dispersing medium, a soluble electrolyte, a pigment and a dispersing agent uniformly dispersing said pigment into the dispersion, is increased by selecting as the dispersing agent an alkali metal salt of a naphthalenesulfonic acid-formaldehyde polycondensate having the general formula: ##STR1## in which R is an alkali metal and n is an integer ranging from about 5 to about 12.

Abstract: An electrocoagulation printing method comprises the steps of (a) providing a positive electrolytically inert electrode having a continuous passivated surface moving at substantially constant speed along a predetermined path, the passivated surface defining a positive electrode active surface; (b) coating the positive electrode active surface with an olefinic substance and silica to form on the surface micro-droplets of olefinic substance containing the silica; (c) forming on the olefin and silica-coated positive electrode active surface a plurality of dots of colored, coagulated colloid representative of a desired image, by electrocoagulation of an electrolytically coagulable colloid present in an electrocoagulation printing ink comprising a liquid colloidal dispersion containing the electrolytically coagulable colloid, a dispersing medium, a soluble electrolyte and a coloring agent; and (d) bringing a substrate into contact with the olefin and silica-coated positive electrode active surface to cause transfer

Abstract: A stabilized electrocoagulation printing ink comprises a liquid colloidal dispersion containing an electrolytically coagulable colloid, a dispersing medium, a soluble electrolyte, a coloring agent and a sequestering agent for completing metal ions generated during electrocoagulation printing. The sequestering agent is present in an amount to prevent the metal ions from causing the colloid to undergo undesirable cross-linking, without adversely affecting electrocoagulation of the colloid.

Abstract: An electrocoagulation printing apparatus comprises a positive cylindrical electrode having a central longitudinal axis extending horizontally and a passivated surface defining a positive electrode active surface, the positive electrode being formed of an electrolytically inert metal; a drive mechanism for rotating the positive electrode about the longitudinal axis thereof at a substantially constant speed; a coating device for coating the positive electrode active surface with an olefinic substance and a metal oxide to form on the surface micro-droplets of olefinic substance containing the metal oxide; and a printing head for forming on the olefin and metal oxide-coated positive electrode active surface a plurality of dots of colored, coagulated colloid by electrocoagulation of an electrolytically coagulable colloid in the presence of a coloring agent, the dots of colored, coagulated colloid being representative of a desired image.

Abstract: An improved electrocoagulation printing method comprising the steps of (a) providing a positive electrode formed of an electrolytically inert metal and having a continuous passivated surface moving at substantially constant speed along a predetermined path, the passivated surface defining a positive electrode active surface; (b) forming on the positive electrode active surface a plurality of dots of colored, coagulated colloid representative of a desired image, by electrocoagulation of an electrolytically coagulable colloid present in an electrocoagulation printing ink comprising a liquid colloidal dispersion containing the electrolytically coagulable colloid, a dispersing medium, a soluble electrolyte and a coloring agent; and (c) bringing a substrate into contact with the dots of colored, coagulated colloid to cause transfer of the colored, coagulated colloid from the positive electrode active surface onto the substrate and thereby imprint the substrate with the image.