Function
The thin material (also known as an "envelope") that covers the large, rounded sections of hot air balloons serves the function of a light bulb during a balloon glow. The burner inside the hot air balloon is lit, causing the light from the flame to illuminate the envelope and make a hot air balloon stand out in the night sky. If the burner is extinguished, then the light in the envelope ceases to be visible, in the same way as a light bulb fades to darkness when no electricity is running through it.
Preparation
Hot air balloons participating in a balloon grow are usually manned by specialist crews who know how to light the balloon to create the required effects. The crew starts by preparing a hot air balloon in a normal way: tweaking the burner so it fills the balloon with hot air and the balloon inflates. The crew then prepares the balloon for flight by performing the usual safety checks.
Environment
Balloon glows take place at night, as the effects of the balloon torches would not be as visible during daylight hours. Each balloon is normally covered with elaborate artwork and symbols. These patterns light up once the torch is ignited, allowing the images to be clearly outlined against the surrounding darkness. Each balloon takes on the role of a paper lantern, but on a much larger, more spectacular scale.
Light and Sound
The light from the balloons is only part of the spectacle at a balloon glow. The balloons are usually launched to the sound of music managed on the ground by a sound engineer and disc jockey. The crews that operate the glowing balloons communicate with the staff on ground controlling the music, meaning they can light up and lower down the torch in time with the music, making for spectacular sound and vision displays.