Abstract: A method and apparatus are disclosed for preventing warp in the manufacture of corrugated board formed from three webs; namely, a single face liner, a medium, and a double face liner. The method includes moisture measurements of the single-face liner and double-face liner over a plurality of zones transverse to the direction of liner motion. For each zone of each liner an iteratively determined asymptotic zonal time average moisture value is calculated. If the zonal time average difference is greater than a predefined amount, corrective action is taken by increasing or decreasing the amount of water sprayed onto the single-face liner for that particular zone. Furthermore, an average moisture content reading for the single-face and double-face liners is taken and if outside a predetermined range, corrective action is taken by adjusting the preheater wrap arm angle for some or all of the webs. Adjustments of the corrective action in view of web speeds are automatically made.