Making the bulbs requires workers to handle mercury in either solid or liquid form because a small amount of the metal is put into each bulb to start the chemical reaction that creates light.

"The 60-watt lamp is the most-sold bulb in America," said James R. Brodrick, the manager for solid-state lighting at the Energy Department.

The technique of rammed bulb and solid inorganic material with high strength is an important way for the improvement of pile bearing and composite foundation reinforcement effect.