In an example, a method includes providing a print agent comprising chargeable particles in a carrier fluid to a print agent concentration apparatus (600). The print agent may be passed between a conveyor (604) and an electrode (602), and a potential applied to cause the chargeable particles to be attracted to the conveyor and to form a concentrated layer of particles on the conveyor. A proportion of the carrier fluid may be separated from the concentrated layer of particles and a thickness of a remaining layer on the conveyor may be measured. It may be determined if the measured thickness of the layer meets predetermined criteria and, if not, an operational parameter of the print agent concentration apparatus may be adjusted.

An image forming apparatus executes a first obtain mode to obtain a resistance value of a developing roller when a potential difference between the developing roller and an electroconductive roller is generated by a second voltage generator when the developing roller carries a reference liquid developer having a known toner concentration. A second obtain mode is executed to obtain a toner concentration of the liquid developer on a surface of the developing roller based on the obtained resistance value and a detection result when a potential difference between the developing roller and the electroconductive roller is generated by the second voltage generator when the liquid developer is applied to the developing roller. During image formation, the controller controls a first voltage generator based on the obtained toner concentration so the toner concentration of the liquid developer on the surface of the developing roller is a target value.

In an example, a method includes collecting (102) print agent from a print agent reservoir to form a print agent layer on a first print agent transfer member (204). The print agent layer may be transferred (104) directly from the first print agent transfer member to a second print agent transfer member (206), where the print agent layer may be heated (106). The print agent layer may be applied (108) directly from the second print agent transfer member to a substrate.

Example aspects described herein relate to an apparatus for adjusting control parameters of a printing substance for a printing system. Such adjustments may occur in conjunction with a color calibration process of the printing system.

An image forming apparatus includes: a plurality of image forming parts each of which transfers a toner image to the transfer medium, the plurality of image forming parts being arranged from an upstream side to a downstream side along a moving direction of the transfer medium; a density detector that detects a density of the toner image; and a hardware processor that performs image stabilization control in which a plurality of patch images is formed while levels of parameters of image formation are changed for each of the image forming parts and the parameters are corrected based on respective densities of the patch images detected by the density detector.

In one example of the disclosure, it is determined that an amount of print agent remaining in a print agent container of a print apparatus is below a threshold level. An amount of print solution is transferred from a print solution reservoir of the print apparatus, or an amount of print solution solvent is transferred from a solvent reservoir of the print apparatus, into the print agent container. At least some of the remaining print agent is caused to dissolve into the amount of print solution or print solution solvent to forma rinse solution. The rinse solution is transferred from the print agent reservoir to the print solution reservoir.

Downtime relating to formation and detection of a detection image is reduced. An image forming apparatus includes a controller configured to calculate a first conversion unit to convert a gradation of input image data so that density output for the input image data becomes a first density output characteristic based on a first detection result of the detection image detected by a density sensor in a first mode. The controller generates a second conversion unit to convert the gradation of the input image data so that the density output for the input image data becomes a second density output characteristic in a second mode based on the detection result in the first mode and correction information, and further updates the correction information based on a second detection result of the detection image detected by the density sensor in the second mode and the first detection result.

An image forming apparatus including: a latent image forming portion configured to form a latent image on an image bearing member; a developing device including a container configured to store toner, and a developing member configured to supply the toner to the latent image formed on the image bearing member to form a toner image; an environment sensor configured to detect environmental information related to an environment in which the developing device is placed; and a controller configured to control switching between a first mode and a second mode, in which a number of prints per unit time is smaller than in the first mode, wherein the controller is configured to perform switching from the first mode to the second mode based on an update value obtained by adding or subtracting over time an index value weighted in accordance with the environmental information detected by the environment sensor.

A developing roller is rotatable while carrying a liquid developer containing toner and a carrier liquid and contains an electroconductive agent, and includes a squeeze roller provided in contact with the developing roller through at least the carrier liquid, a voltage source capable of generating a potential difference between the developing roller and a squeeze roller, and a current detecting sensor for detecting a current passed between the developing roller and the squeeze roller. In addition, a controller controls the voltage source, and a display device outputs information on a lifetime of the developing roller. The controller outputs the information on the lifetime from the display device on the basis of a detection result by the current detecting sensor when a predetermined potential difference is generated between the developing roller and the squeeze roller by the voltage source.

An example printing system for printing liquid ink has a developer device to transfer ink to an image plate of the printing system. The developer device has an ink inlet to receive ink from an ink reservoir of the printing system; a developer roller to transfer ink to the image plate, a motor to rotate the developer roller, and an ink sensor to detect arrival of ink at the developer device. The printing system is configured to start the motor in response to the ink sensor detecting arrival of ink at the developer device.