UNIVERSITY PARK, Pa. -- For years, companies have been adding whiteners to laundry detergent, paints, plastics, paper and fabrics to make whites look "whiter than white," but now, with a switch away from incandescent and fluorescent lighting, different degrees of whites may all look the same, according to experts in lighting.
"Retailers have long been concerned with the color-rendering qualities of their lighting, but less aware how light sources render white," said Kevin W. Houser, professor of architectural engineering, Penn State.
Not long ago, the only practical choices for home, office or commercial lighting were incandescent or fluorescent bulbs. More recently, compact fluorescent bulbs, which use less energy than incandescent bulbs, became popular, but compact fluorescents are not always accepted by consumers because of poor color rendition, lack of dimability, slow warm-up to full output and because they contain mercury.
The most recent popular entry into home or commercial lighting are light-emitting diode (LED) bulbs, which while currently expensive, are often even more energy-saving than compact fluorescents.
While some LED bulbs will make colors pop, the vast majority do not showcase or differentiate the appearance of white products, according to Houser, because all white light is not the same.
Different light sources contain different combinations of the wavelengths of light. A broad variety of wavelengths will create light that appears white to the human eye, but different mixtures of wavelengths will affect how colors are rendered. When it comes to seeing the color white, the light source is very important because of how product manufacturers make white products appear white using whiteners.
Whiteners contain fluorescent materials that glow under violet and ultraviolet light. Sunlight, fluorescent light and incandescent light all produce some light in the violet and ultraviolet range. The whiteners used in consumer products work under those conditions, resulting in a bright white perception.
However, most current LED bulbs use blue LEDs to excite a phosphor that then glows white, but produces no violet or ultraviolet light.