Which was used by Montgolfier brothers to launch the first piloted ascent of an air balloon?

Joseph-Michel Montgolfier (26 August 1740 – 26 June 1810) and Jacques-Étienne Montgolfier (6 January 1745 – 2 August 1799) were paper manufacturers from Annonay, in Ardèche, France best known as inventors of the Montgolfière-style hot air balloon, globe aérostatique. They launched the first piloted ascent, carrying Jacques-Étienne. Joseph-Michel also invented the self-acting hydraulic ram (1796), Jacques-Étienne founded the first paper-making vocational school and the brothers invented a process to manufacture transparent paper.

Of the two brothers, it was Joseph who was first interested in aeronautics; as early as 1775 he built parachutes, and once jumped from the family house. He reported some years later that he was watching a fire one evening while contemplating one of the great military issues of the day—an assault on the fortress of Gibraltar, which had proved impregnable from both sea and land. Joseph mused on the possibility of an air assault using troops lifted by the same force that was lifting the embers from the fire. He believed that the smoke itself was the buoyant part and contained within it a special gas, which he called "Montgolfier Gas", with a special property he called levity, which is why he preferred smoldering fuel.