Then the tube is evacuated again until it reaches a vacuum of 10-3 torr. Argon or neon is back filled to a specific pressure depending on the diameter of the tube and sealed off. Red is the color neon gas produces, neon gas glows with its characteristic red light even at atmospheric pressure. Neon tubes actually refer to all positive-column discharge lamps, regardless of the gas filling. The mercury spectrum is rich in ultraviolet light which in turn excites a phosphor coating on the inside of the tube to glow.
Phosphors are available in most any pastel colors.
Special thanks goes to Daniel Preston for providing Inventors with technical information and corrections for this article. Mr. Preston is an inventor, an engineer, a member of the technical committee of the International Neon Association and the owner of Preston Glass Industries . Special thanks goes to Eileen Garrett, owner of Empress Signs , for providing the photos of neon signs. Special thanks goes to artists, Eric Ehlenberger and Craig A. Kraft for providing the photos of their neon sculptures. Neon University Source of books and tapes on making neon, newsgroups and a list of schools and courses for learning the art of neon.