Except for the entrance areas, most caves are in perpetual darkness, and cavers can only explore new passages by bringing in their own light sources. For over 75 years, the carbide lamp was the most popular and reliable light available. This lamp was used by Jan Cann and her husband Herb as they explored over 60 miles of Jewel Cave National Monument.
Water from an upper chamber slowly drips into a lower chamber filled with small gravel-like chunks of calcium carbide. The ensuing chemical reaction releases pressurized acetylene gas, which is forced through a small nozzle in the center of a polished metal reflector. Swiping one’s palm across a flint striker, mounted on the edge of the reflector, creates a spark that ignites the acetylene and produces a bright yellow-white flame. Properly maintained, the flame can burn cleanly for 3-4 hours. When the carbide is used up, the caver must unscrew the bottom chamber to scrape out the inert calcium hydroxide, and refill the chamber with fresh carbide. The flame length and brightness is proportional to the rate that water drips into the carbide, which is controlled by lever on the top of the lamp.
Over the last 20 years, rechargeable electric lamps have become much more efficient and reliable, and the quality of light now surpasses that of the carbide lamp. They are also lightweight and require very little maintenance. For these reasons, cavers now rely almost exclusively on electric lighting to explore the mysteries of the caves they love.