Spring Point Ledge Lighthouse was constructed much too late to use the whale oil that powered the early lighthouses. Instead, Spring Point used mineral oil, but exactly which type is unclear. The term “mineral oil” is widely and loosely used to describe several different types of oil, including those distilled from petroleum and those from other sources. The mineral oil used in Spring Point’s lamp was probably very closely related to kerosene.
The original lamp had a single wick on a base which held the fuel supply. The lamp was topped by clear glass, similar to those used on lanterns and hurricane lamps. This glass chimney vented into a metal chimney that extended upward from the top of the Fresnel lens to the ball vent on top of the lantern room and the smoke was vented outside through holes in the ball vent. This kept most of the soot away from the lamp chimney and the lantern room windows. Cleaning the inside of the lens, the glass chimney, and the inside of the windows of soot from the lamp was probably an ongoing part of the keepers’ duties. Later, the single-wick lantern was replaced with a mantle lantern which reduced the fuel burn to a pint and a half a night.
The lighthouse was electrified in 1934 and the kerosene lamp was replaced by a light bulb. When the lighthouse was automated in May 1960 and the Fresnel lens was replaced with a 375mm barrel lens, which did not rotate, the lightbulb was operated with a flasher.
Today, Spring Point light is powered by a small 36-watt incandescent lamp. The fact that it can be seen for about 14 miles, or roughly to the horizon line, is a testament to the resolving power of the Fresnel lens. Several of the small bulbs are mounted in a carousel mechanism that rotates a new bulb into position when the one in use burns out. The Coast Guard technicians replace the burned out bulbs during routine maintenance inspections.