Tallow from beef or mutton and lard from pigs both burn well in a wick lamp, and a 240 ml cup of rendered fat lasts roughly 8 to 10 hours at a moderate wick. Fat burns with more smoke than olive oil or kerosene, so use clean, well-strained fat, trim the wick often and ventilate the room. Never put water on burning fat.
Part of Oil Lamp Construction
Tallow, lard and poultry fat are solid or soft at room temperature, so a fat lamp melts a small pool at the wick and cannot spill liquid fuel when it is cold.
Rendered Fat Burns Because The Wick Melts It
Any animal fat can be rendered into lamp fuel. The ones the oil-lamp overview lists are:
- Tallow (beef or mutton fat) — steady flame, moderate smoke. Available whenever you slaughter livestock or hunt large game.
- Lard (pig fat) — slightly softer than tallow, burns well.
- Poultry fat (chicken, duck, goose) — liquid at room temperature, burns cleanly but is used up faster.
- Fish oil — burns brightly but smells terrible; use it outdoors or in a workshop.
- Bear or deer fat — excellent lamp fuel, according to the overview.
Tallow and lard are solid at room temperature. That is useful: a cold fat lamp cannot spill liquid fuel. The flame’s own heat melts a small pool around the wick, and the wick draws from that pool. To start a cold lamp, hold the wick tip in the pool of fat you have melted first, or warm the dish gently, so that the wick is already wet before you light it. A dry wick burns itself rather than the fuel.
Burn Rate Tells You How Much Fat To Keep
The overview’s figures for a moderate wick are about 25 ml/h for tallow and about 28 ml/h for lard.
Worked example. A 240 ml cup of rendered fat:
- tallow: 240 ml ÷ 25 ml/h = 9.6 h
- lard: 240 ml ÷ 28 ml/h = 8.6 h
That matches the overview’s “roughly 8-10 hours”, enough for an evening’s work. Poultry fat is consumed faster, so expect fewer hours from the same cup.
Clean Fat Burns Cleanly
- Strain it. Cracklings and meat fragments char on the wick and clog it. See Rendering Fat for Lamp Fuel.
- Keep water out. Water trapped in fat makes the lamp spit and sputter, because it boils as it reaches the hot wick. Let rendered fat settle and cool, then lift the fat off the water layer.
- Use the whitest fat. The overview says the whiter the fat, the cleaner it burns.
Common Mistakes
- Expecting a cold lamp to light from a dry wick. Pre-wet the wick in melted fat first.
- Using fat with meat scraps in it. Scraps char and smoke. Strain again.
- Choosing fish oil for indoor use. It smells terrible and is better kept for workshops or outdoor lamps.
Safety
Fat fires and soot
A fat lamp that is knocked over spreads burning fat, which sets and sticks as it cools. If burning fat spreads, smother it with a metal lid, a plate or dry sand or earth. Never use water on burning fat: it sinks under the fat and flashes to steam, throwing burning fat. Fat also makes more soot than olive oil or kerosene. Soot means the flame is not burning completely, and incomplete burning makes carbon monoxide, which has no smell and whose early symptoms (headache, nausea, drowsiness) feel like ordinary tiredness. Ventilate the room with an inlet and an outlet. See Soot & Ventilation.
What’s Next
- Learn next: Rendering Fat for Lamp Fuel — turning trimmings into strained fuel
- Combine with: Fat Preservation — keeping rendered fat from going bad before you burn it