Open shells and "frogs" (1820-1900)

The lamps that were referred to as "frogs" due to their shape were operated with tallow or rapeseed oil. Frog lamps are available in different designs and were mainly named after their origin. The most famous models were therefore called Harz Frog, Westphalia Frog and Saarland Frog. Like the open shells, they were very dangerous due to the open flame and caused numerous major accidents as a result of gas and dust ignition related to coal mining.