Image #27-58 © General Electric Lighting Company
The high-pressure sodium (HPS) fixtures in this image are mounted at a height of 105 feet, and put about 120 to 130 foot-candles of light on the factory floor. Before the advent of HPS lamps, many factories used carbon-arc, mercury-vapor, and incandescent lamps -- sometimes in combination. But these suffered from a variety of shortcomings. Carbon arcs needed lots of maintenance, mercury lamps had poor color, and incandescent lamps were dim and short-lived.
HPS seemed a good compromise. The color was rather yellow -- different but not necessarily worse than the blue tinge of mercury-vapor lamps. Life-ratings started at about 6,000 hours and increased when manufacturers introduced improved versions. And the lamps produced about 100 lumens per watt, compared to about 30 lpw for high-wattage incandescent lamps.
© 2001 Smithsonian Institution
Last Updated: February 2000