Abstract: Color densities of patches included in a control strip are measured to perform printing control based on the color densities. The patches are arranged in the same direction as the arrangement of ink keys of a printing device. The patches include four typical patches of black, cyan, magenta, and yellow at area rates of 60 to 85% in the width of each ink key. The printing control is the control for keeping the color densities of the four typical patches of the width of each ink key in predetermined color-density ranges.

Abstract: Color densities of patches included in a control strip are measured to perform printing control based on the color densities. The patches are arranged in the same direction as the arrangement of ink keys of a printing device. The patches include four typical patches of black, cyan, magenta, and yellow at area rates of 60 to 85% in the width of each ink key. The printing control is the control for keeping the color densities of the four typical patches of the width of each ink key in predetermined color-density ranges.

Abstract: A dampening water controller for controlling the concentration of an etching solution in dampening water circulatively used in offset printing, includes an ion concentration measuring means capable of measuring the concentration of at least one kind of ion (object ions) selected from specific anions or cations contained only in an etching solution in dampening water. Information on the measured concentration of the ions in the dampening water is output. A dampening water temperature measuring device capable of measuring the temperature of the dampening water and outputting information on the measured temperatures is provided. Also, an ion concentration information correcting device is provided capable of correcting the information on the measured concentration of the ions in the dampening water, in accordance with the information on the measured temperature of the dampening water.