A calculating portion 300 acquires resistance of a carrier liquid in a carrier tank. A resistance calculating portion 302 acquires the resistance of the carrier liquid on the basis of a liquid amount of a carrier liquid for each of numbers of times of passing of the carrier liquid through a separation and extraction device and resistance of the carrier liquid for each of the numbers of times of passing of the carrier liquid through the separation and extraction device. The liquid amount of a carrier liquid for each of numbers of time of passing is calculated by a deterioration degree distribution calculating portion 301 and is stored in a memory 201. As regards the resistance of the carrier liquid for each of the numbers of times of passing, the resistance of the carrier liquid after passing through the separation and extraction device is stored in the memory 201 in advance for each of the numbers of times of passing. A carrier supply discriminating portion 202 discriminates whether or not a carrier liquid for supply should be supplied, on the basis of the acquired resistance of the carrier liquid. A controller 200 controls a pump 51 for supply on the basis of this discrimination.

According to one example, there is provided an electrostatic printer. The printer includes a photoconductor member, an imaging unit to generate a latent electrostatic image on the photoconductor member, a developer unit including a colored toner, the developer unit to develop a colored toner image on the photoconductor member using an associated base developer voltage, and a controller. The controller is to obtain image data including color separation data representing a variant of the colored toner, to control the imaging unit to generate a latent electrostatic image on the photoconductor member in accordance with the obtained color separation data, to determine a variant developer voltage corresponding to the variant of the colored toner, and to control the developer unit to develop a toner image on the photoconductor member using the variant developer voltage to develop a toner image corresponding to the variant of the colored toner.

An example method of performing a null cycle in a liquid electrographic printer is described. The method involves collecting, at a photo imaging plate cleaning station, imaging oil deposited on a photo imaging plate during a print cycle. During a null cycle, the photo imaging plate cleaning station is controlled to apply the collected imaging oil to the photo imaging plate.

Measures for controlling an engagement force between a photo imaging plate (110) and a developer roller (200) in a printing device (100) are described. A motor (310) is operated to generate rotational motion. The rotational motion is translated into linear motion. The linear motion causes an adjustment to the engagement force between the developer roller and the photo imaging plate. A characteristic of the motor is monitored. The motor is controlled on the basis of the monitored characteristic in order to maintain a desired engagement force between the developer roller and the photo imaging plate.

In some examples, a printing liquid developer includes a developer roller that has a hollow tubular base body formed of a material comprising conductive carbon fiber, a conductive, compliant layer around an outer surface of the hollow tubular base body, and an electrically conductive support separate from the hollow tubular base body and electrically contacted to a surface of the hollow tubular base body.

An image forming apparatus includes a conductive medium, an applying device, and a developing device. The applying device applies conductive liquid to a surface of the conductive medium to form an invisible image. The developing device adheres charged particles to the invisible image formed on the surface of the conductive medium to form a visible image.

An example system includes a power supply. The power supply is electrically coupled to an electrode, a developer roller, and a cleaner roller. The system also includes a controller. The controller is to instruct the power supply to reduce, at a first time, a magnitude of an electrode voltage supplied to the electrode. The controller also is to instruct the power supply to set, at a second time, a developer roller voltage and a cleaner roller voltage each to about a wet null voltage.

Example implementations provide a method of controlling an ink developer used in electro-photography; the method comprising, following cessation of printing, varying a plurality of voltages associated with movement of ink within the ink developer at temporally disparate times.

According to one example, there is provided an electrostatic printer. The printer comprises a photoconductor member, an imaging unit to generate a latent electrostatic image on the photoconductor member, an interface to receive a developer unit comprising a colored toner, the developer unit to develop a colored toner image on the photoconductor member using an associated base developer voltage, and a controller. The controller is to obtain image data comprising color separation data representing a variant of the colored toner, to control the imaging unit to generate a latent electrostatic image on the photoconductor member in accordance with the obtained color separation data, to determine a variant developer voltage corresponding to the variant of the colored toner, and to control the developer unit to develop a toner image on the photoconductor member using the variant developer voltage to develop a toner image corresponding to the variant of the colored toner.

A development device includes a developer bearing member and a magnet which is fixed inside of the developer bearing member. The magnet includes a first magnetic pole for developing a latent image, a second magnetic pole adjacent to the first magnetic pole and being an opposite pole to the first magnetic pole, and a third magnetic pole adjacent to both the first and second magnetic poles and having an opposite pole to the first magnetic pole. A developer regulation portion is disposed such that when a maximum peak amount of a magnetic flux density of the first magnetic pole in a normal direction of the developer bearing member is defined as positive, the magnetic flux density of the first magnetic pole becomes positive in an entire region from a downstream side of the regulating member in a rotary direction of the developer bearing member and through a developing area.