Ultra Violet dye additives are specially formulated to fluoresce in the presence of UV light rays
The overall intensity of UV light diminishes as you move from the invisible UV light range to purple, then to blue and so on down the chart
A correctly tuned Ultra Violet lamp should predominantly emit invisible UV light waves with only a trace of visible "purple" or "blue" light
The small amount of visible light is required to direct the user's eyes to the leak search area, while the invisible UV light rays actually illuminate the leaking dye
Lamps that emit large amounts of visible blue light have been marketed heavily as being more powerful and more effective at fluorescing leaks, backed by the obvious high output of visible light
Special "blue blocking" glasses are required for use with these high output blue lamps in order to remove the nuisance blue light from the vision of the user during the leak search process