Abstract: A photoflash lamp of generally flat configuration for providing compact containment of metal fuel and solid oxidant includes a plate member having a recess therein. An expandable sheet member is formed over, and affixed to the plate surface adjacent to the recess for tightly containing a quantity of combustible material and solid oxidant within the recess. Ignition of the combustible material generates gaseous oxygen and reaction products which expands the sheet member away from the plate surface so as to provide an expandable volume to accommodate the burning oxygen-fuel mixture and to provide increased surface area for permitting maximum light emission.