To create the earliest form of gunpowder, 3 substances were mixed together which included, sulphur, charcoal, and saltpeter which is comprised potassium nitrate. Because these ingredients have varying specific densities, they constantly separated when mixed, forcing soldiers to re-mix gunpowder after having been transported to the battlefield. By the end of the 15th century, a new technique for the manufacturing of gunpowder emerged, that of corning which made gunpowder much more reliable. Corning involves mixing together the 3 primary ingredients to create a slurry. This is more effective than the traditional method because as the mixture dries, the ingredients do not separate due to their different specific gravities. This acts to increase the stability of gunpowder and allowed cannons to evolve into lethal siege engines no longer governed by the strength of soldiers or the laws of mechanics. Gunpowder, the first chemical explosive ever invented, was the driving force behind the weaponry used against fortifications, hurling projectiles faster, further, and with greater force than previously designed mechanically powered machinery (e.g. trebuchet, catapult, ballista etc.)