Abstract: There is disclosed a radiant energy device for bonding thermoplastic films without contact between the plastic films and the radiant energy sources in the form of resistance wires heated to incandescence by pulses of current timed to occur when the plastic films have been supported in tension and the wires have been brought to a point of close proximity to but spaced from the films. The wires are received in contoured reflecting cavities to focus and control the radiant energy, and the cavities are ducted to a source of coolant fluid which is applied in pulses timed in relation to the current pulses to cool and solidify the plastic seals and to cool the system to a reference temperature level at the conclusion of each cycle so that uniform sealing standards can be maintained. Resiliently biased, movable end supports for the wires maintain uniform tension under changes of wire length with temperature so that the distance of the wires from the films is uniform and unchanging at all points along its length.