Plastic explosive is a soft and hand-moldable solid form of explosive material. Within the field of explosives engineering, plastic explosives are also known as putty explosives or blastics. Plastic explosives are especially suited for explosive demolition. Common plastic explosives include Semtex and C-4. The first manufactured plastic explosive was gelignite in 1875, invented by Alfred Nobel. Usage Plastic explosives are especially suited for explosive demolition of obstacles and fortifications by engineers, combat engineers and criminals as they can be easily formed into the best shapes for cutting structural members and have a high enough velocity of detonation and density for metal cutting work. An early use of plastic explosives was in the warhead of the Petard demolition mortar of the British Armoured Vehicle Royal Engineers (AVRE); said mortar was used to destroy concrete fortifications encountered during Operation Overlord (D-Day). The original use of Nobel 808 supplied by the SOE was for sabotage of German installations and railways in Occupied Europe. They are generally not used for ordinary blasting as they tend to be significantly more expensive than other materials that perform just as well in this application. A common commercial use of plastic explosives is for shock hardening high manganese percentage steel, a material typically used for train rail components and earth digging implements. Reactive armor in tanks uses plastic explosives sandwiched between two plates of steel. Incoming high explosive shaped charge anti-tank rounds pierce the outer steel plate, then detonate the plastic explosive. This disrupts the energy from the incoming round and shields the tank. History The first plastic explosive was gelignite, invented by Alfred Nobel in 1875. Prior to World War I, the British explosives chemist Oswald Silberrad obtained British and U.S. patents for a series of plastic explosives called "Nitrols", composed of nitrated aromatics, collodion, and oxidising inorganic salts. The language of the patents indicate that at this time, Silberrad saw no need to explain to "those versed in the art" either what he meant by plasticity or why it may be advantageous, as he only explains why his plastic explosive is superior to others of that type. One of the simplest plastic explosives was Nobel's Explosive No. 808, also known as Nobel 808 (often just called Explosive 808 in the British Armed Forces during the Second World War), developed by the British company Nobel Chemicals Ltd well before World War II. It had the appearance of