The incendiary paint theory (IPT) was proposed in 1996 by retired NASA scientist Addison Bain, stating that the doping compound of the airship was the cause of the fire, and that the "Hindenburg" would have burned even if it were filled with helium. The hypothesis is limited to the source of ignition and to the flame front propagation, not to the source of most of the burning material, as once the fire started and spread the hydrogen clearly must have burned (although some proponents of the incendiary paint theory claim that hydrogen burned much later in the fire or that it otherwise did not contribute to the rapid spread of the fire). The incendiary paint hypothesis asserts that the major component in starting the fire and feeding its spread was the canvas skin because of the compound used on it.