For over 40 years, miners have been extracting sulfur from the crater of Kawah Ijen in Indonesia. To double their meager income, the hardiest of these men work nights, by the electric blue light of the sulfuric acid exhaled by the volcano. As the light of day recedes, an eerie incandescence appears to rise from the depths of the Kawah Ijen crater. The high-temperature liquid sulfur that flows from an active vent at the edge of the world’s largest hydrochloric acid lake flares in blue flames that can reach up to 5 meters. At the foot of the glow, miners bustle amidst the toxic fumes. They are monitoring the flow of molten sulfur as it pours out of pipes at 115 °C (239°F), and its subsequent crystallization. Breaking up, gathering up, loading up and transporting the coagulated blood of the earth earns them a living. By the blue light of the flare, they extract hunks of sulfur, then carry them up the flank of the crater to sell for 680 roupees per kilo (about €0.04 or 5 cents US). But the loads they carry, weighing between 80 and 100 kilos (176 lbs - 220 lbs), cost them their health—and sometimes their life. By working nights, they manage to haul out two loads every 24 hours, doubling their salary, avoiding the daytime heat of the Kawah Ijen cauldron, and despite the condition remaining independent The sulfur, among the purest in Indonesia, is destined for the food and chemical industry. Whitening sugar, at the price of their health and youth, such is the destiny of these serfs to sulfur. In 2008, Olivier and his friend Régis Etienne heard about these strange blue flames. They will be going on several occasions on the volcano and will spend 30 nights in the crater for filming and photographing (in highly difficult conditions) the miners who continue to work at night in the middle of the blue flames of Kawah ijen. See More Photography at oliviergrunewald.com.