Inflammare or the Ignition Charm is used to ignite flame wherever the wand is directed. Unlike Incendio which conjures a fire wherever the wand is pointed, Inflammare will ignite anything in a drawn path of the caster's wand, as seen with Tracey Davis in Chapter 78. "Tracey yelled, her voice high with strain, 'Inflammare!' and the Sunshine charge came to another sudden halt as a line of fire blazed up between them in the half-dry grass, extending to follow the path of Tracey's wand as she pointed it; an instant later Susan Bones cried 'Finite Incantatem!' and the flames dimmed, brightened, dimmed in the contest of their wills..." It seems that it is up to the caster to determine how powerful the flames should be, as Harry later uses it to singe Lord Voldemort's cloak. "Harry used Inflammare to singe Voldemort's robes where they lay..." (Ch. 115)