Based upon the exothermic reaction that takes place between aluminium or magnesium and platinum or palladium after a critical temperature has been reached, an interesting new product has been developed by the Sigmund Cohn Corporation of Mount Vernon, New York. This comprises a composite wire having a core of aluminium with a sheath of palladium. The wire is strong and ductile, but when heated to about 650°C by the passage of a current it ignites with explosive violence and reaches a temperature of about 2000°C. A similar product is also available in the form of laminated sheet. Applications are expected to develop in the field of detonating devices.