A self-contained and sealed package of exothermic welding material includes a cup-shape disposable ceramic container for such material which is closed at the top with a heat consumable cap. The bottom of the container includes a tap hole, the lower end of which is also closed with a formed cup-shape heat consumable disk. An insulated wire pair extends along an axial groove in the exterior of the container and through a radial groove through the lip of the cup beneath the cap. The end of the wire pair within the container has the insulation removed to form a spark gap which end extends at an angle away from the interior of the container and is embedded in the exothermic material. The ends of the wire pair outside the container have the insulation removed to a greater extent so that the wires can readily be bent and connected to power unit for generating a high energy spark at the gap. The package is mounted unopened on a seat on a refractory mold above a weld cavity which contains the parts to be welded and a hinged baffled mold cover closed. The wire pair having been bent to extend beneath the cover is connected to the spark generator. When the exothermic material is ignited the heat causes the package cap to be consumed and as the reaction proceeds the disk is consumed permitting the molten metal produced by the reaction to drop into the weld cavity. A major portion of the slag formed in the reaction remains in the ceramic container and is disposed of with the container while the refractory mold is reused.