A system which controls via controller (100) image dependent curl by moisturizing a sheet immediately after fusing by rollers (62,64) determines critical machine and environmental characteristics through a series of on-line sensors. An operator selectable table is used to indicate the type of sheet loaded in each sheet holding tray. Machine software then uses this information to determine how much moisture should be added to each side of the sheet in order to achieve a flat sheet when it reaches equilibrium. The moisture is added by transfer rolls (102,103) which are driven at a variable speed by servo motors (115) in the opposite direction to sheet movement to vary the quantity of moisture that is added to each side of the sheet.