Abstract: A steam finishing platen having a work surface through which steam and air can pass. The platen includes up-steam piping within a chamber defined by the platen, and a vacuum port to that chamber. A steam damper is movable between a normally open position where the vacuum port is open to a vacuum source, and a closed position where the damper closes the vacuum port when steam is provided to the up-steam piping. A steam piston, located within the platen chamber, is connected by a spring loaded linkage to the steam damper, and is connected by a steam line to the up-steam piping. When steam is provided to the up-steam piping for steaming a fabric workpiece on the platen, the steam actuated piston closes the steam damper, thereby automatically closing the vacuum port to that steam within the platen chamber.