The light from LPS lamps, however, is stark yellow. In their glow, everything appears either yellow, black, or some shade of gray, although some studies indicate that contrasts are clearer in LPS light, making them very good for street lighting. Largely because of the color, LPS lamps have sold poorly in the United States, compared to Europe. An alternative to LPS lamps appeared at almost the same time. Mercury-vapor lamps introduced in 1932 by England's GEC were easy to use and produced 40 lpw.
Many people find the blue-green color a bit garish, though.
Researchers have tried for years to overcome this drawback, principally through the use of phosphors, with only modest success. Dissatisfaction with the color of these lamps helped to drive innovation in both types in the 1950s and 1960s. Scientists at General Electric invented a new ceramic material called polycrystalline-alumina, or Lucalox, that allowed sodium lamps to operate at high pressure. HPS lamps with even better color have been developed, but their output drops still lower to the 40 to 60 lpw range. At about the same time, the effect of dosing mercury-vapor lamps with halide compounds of various metals was under study by several inventors in West Germany and at General Electric.