Electrophotographic printing

A method of controlling electrophotographic printing apparatus comprising:—

• an image-forming member having a surface on which a latent electrostatic image can be formed and developed for transfer of the developed image to a substrate,
• a developer for depositing onto the surface of the image-forming member a layer of ink comprising charged ink particles to develop the latent image;
• an intermediate transfer member for transferring the developed image to a substrate;
• and
• an adjustable voltage supply for generating electric potential between the surface of the intermediate transfer member and the surface of the image-forming member such that the developed image formed on the surface of the image-forming member is transferred to the surface of the intermediate transfer member;
• the method comprising controlling the voltage supply to adjust the electrical potential to affect the transfer of ink to the intermediate transfer member from the image-forming member.

A method of calibrating an electrophotographic printing apparatus comprising:—

• an image-forming member having a surface on which a latent electrostatic image can be formed and developed for transfer of the developed image to a substrate,
• a developer for depositing onto the surface of the image-forming member a layer of ink comprising charged ink particles to develop the latent image;
• an intermediate transfer member for transferring the developed image to the substrate;
• and
• an adjustable voltage supply for generating electric potential between the surface of the intermediate transfer member and the image-forming member such that the developed image formed on the surface of the image-forming member is transferred to the intermediate transfer member,
• the method comprising:—
• using the electrophotographic printing apparatus to print on one or more substrates a set of images, wherein each image of the set of images is printed with a different electrical potential provided between the intermediate transfer member and the image-forming member,
• measuring the optical density of each of the set of images, and
• setting the electrophotographic printing apparatus to use, for future printing, the electrical potential between that image-forming member and the intermediate transfer member that produced an image of the set of images with a required optical density.