Image forming method, image forming apparatus, and set of ink and processing fluid

An image forming apparatus comprising:

• a processing fluid application device configured to apply a processing fluid to a recording medium;
• an ink application device including nozzles including an extreme downstream nozzle in a direction of recording medium conveyance, the ink application device being configured to apply an ink to the recording medium onto which the processing fluid has been applied;
• and
• a heating device configured to heat the recording medium onto which the processing fluid has been applied,
• wherein the ink comprises a black ink and at least one color ink other than the black ink,
• wherein the following relationship is satisfied:
• |γ(k)-γ(c)|≤5 mN/m, where γ(k) represents a dynamic surface tension of the black ink at a surface lifetime of 15 ms and γ(c) represents a dynamic surface tension of the at least one color ink at a surface lifetime of 15 ms,
• wherein a time taken for the recording medium onto which the ink has been applied to pass through a vicinity of the heating device or a position in contact with the heating device is 1.5 seconds or less after the ink discharged from the extreme downstream nozzle is applied to the recording medium.

A set comprising:

• an ink comprising a black ink and at least one color ink other than the black ink;
• and
• a processing fluid,
• wherein a time taken for the recording medium onto which the ink has been applied to pass through a vicinity of the heating device or a position in contact with the heating device is 1.5 seconds or less after the ink discharged from the extreme downstream nozzle is applied to the recording medium,
• wherein the following relationship is satisfied:
• |γ(k)-γ(c)|≤5 mN/m, where γ(k) represents a dynamic surface tension of the black ink at a surface lifetime of 15 ms and γ(c) represents a dynamic surface tension of the at least one color ink at a surface lifetime of 15 ms.