Abstract: An oven for firing ceramic materials which is provided with a firing chamber and with a plurality of rotatable transverse rollers for advancing the material to be fired along the chamber. The oven is provided with a horizontal auxiliary surface disposed in the lower part of the chamber, spaced from the material being fired, and with means for displacing the auxiliary surface longitudinally along the chamber in a direction opposite to the direction of travel of the material being fired. The vertical distance from the auxiliary surface to the roller axes is preferably not less than twice the axis-to-axis spacing between the rollers and not more than twice such roller spacing plus the diameter of the rollers. The speed of travel of the auxiliary surface is a submultiple of the speed of travel of the material being fired. The auxiliary surface is preferably constituted by a plurality of plates bearing on the oven floor and actuated for displacement in a preferably intermittent manner by thruster devices.