Abstract: An apparatus (11) for conditioning media, for example a moving web (12) of receptor material in an electrostatographic printer (10), is described. The apparatus (11) comprises a heating system, such as a heated drum (55), to adjust the moisture content of the media and a cooling system (65) for cooling the heated media. A moisture sensor such as an electrometer (74) determines the moisture content e.g. by an electrical condition of the media before it leaves the apparatus (11). The moisture sensor (74) controls the heating system (55). A temperature sensor (81) determines the temperature of the media after cooling. This sensor (81) may control the cooling system (65) or other parameters of the system. By conditioning a receptor material in an electrostatographic printer, a higher yield of toner transfer can be obtained. Optionally two electrometers (74a, 74b) are used to thereby detect the charge decay on an earthed metal drum (72).