My novel is set in an underground city. Never, at any point in the story, do the characters leave this city. Food, water, and shelter are still essential, but the uniqueness of the situation makes lighting, heat, and ways of keeping time just as important.
Tallow candles, candles made from condensed fat, are the source of light for the poorest of the poor. They are smoky, they smell, provide little light, and burn quickly. Even the common humans prefer to use other sources, and these are kept as emergency reserves.
Wax candles are more common to craftsmen, in particular, as they create less smoke and last longer than tallow. In addition, wax candles can be marked and burned to provide clocks. Less practical, ornate candles are also used in the highest districts, as they are more aesthetically pleasing than oil lanterns. Carving out elaborate candles is an established form of art.
Ever-burners are candle hybrids; they provide only a pin-prick of light, and are most commonly used for marking pathways. These candles are made to last far longer than most candles, and can be found along servant’s hallways, roads, and many public buildings in the upper quarters. The University also uses them as decorations in one of their larger hallways to recreate the major star formations on special occasions.
Torches are also used by the poor, and are by and large considered better alternatives for those who would otherwise be using tallow candles. Torches are usually made out of twisted scrap wood that can not be used for building (as plant material that grows from geothermal heat is farmed professionally for its by-products in the lower and warmer levels). The drawback to torches is that in caves and tunnels, the air can hold pockets of flammable gases, and they are not the safest source of light available. They will burn for a little over an hour.
This is the safest source of light to use, a good oil lamp is expensive. The best are cased in metal and glass, and have mechanisms inside for lighting the wick, for trimming the wick, and for extinguishing the flame quickly. Different models are available, and because the Mordache are good with glass work, some can be very fragile. Some oil lamps are little more than open flames, wicks dipping into a glass sphere with the flame out in the open (usually hung from the ceiling), some are meant to be stationary pieces.
Phosphorus was first made by distilling off phosphorus vapor from precipitated phosphates heated in a retort. The precipitated phosphates were made from ground-up bones that had been de-greased and treated with strong acids. (From Wikipedia: link.)
Sounds lovely, doesn’t it? In addition to being a low-heat light source (the lamps in Vastii glow from four hours to almost five days, depending on the mixture), making phosphorus can poison and kill the chemist trying to distill it. The method above describes the first commercial use of phosphorus in the 19th century, but as light is so important in Vastii, and since phosphorus can be discovered in urine, it’s not unreasonable to adopt the same refining techniques.
Phosphorus is flammable, however it does not burn hot, and doesn’t need much oxygen. The typical phosphorus lamps are glass globes, sealed, and bound with metal. The advantage to phosphorus lamps is that they can be swung, turned on their sides, and as long as the seal remains in place, they won’t explode if exposed to very flammable gases.
Very commonly seen in the first several levels: public lighting is a sign of wealth, and the most impressive are fire bowls, metal bowls bearing burning oil mixtures. Depending on what has been added to the oil, the color of the flame can be changed to purple, red, orange, green, or blue. These bowls are set on the ground, or hung like a chandelier.
The most impressive fire bowl in the city is in the Arena, where a balcony that hangs over the Pit uses oil like a fountain. The exterior of the Arena is sculpted in the form of a reclining god, over a hundred feet fall and spanning the four levels that the Arena cuts through, and this balcony is an outstretched hand in the center of the city. Formally, this balcony was used as a place of execution. During special events, oil will seep along the edges and create a burning fountain, droplets of burning oil falling into the Pit and attracting attention all through the city with the spectacle.