My Favorite Plastic Explosives 4 January 2010, Cervera de los Montes A4 (29,7 x 21,0 cm) Ballpoint pen and felt-tip pen on paper i Plastic explosive, invented by Alfred Nobel in 1875, is a specialized form of explosive material. It is soft and hand moldable solid material. Many terrorist groups have used plastic explosives, especially Semtex and C-4. Helsinki Art Museum. 442 / 779