A closed reservoir lamp is a small metal tin, glass jar or ceramic vessel with a wick threaded through a hole in the lid, leaving about 1 cm of wick exposed. The lid stops spills and slows evaporation, but the reservoir must still be able to draw in air as fuel leaves, and the lamp should burn fat or vegetable oil, not kerosene.
Part of Oil Lamp Construction
A lidded reservoir with a wick through the lid spills less and loses less fuel to evaporation than a dish. The wick hole must still let air in as fuel is drawn out.
A Lid Fixes Spills But Adds An Air Problem
The overview’s build:
- Find a small metal tin, glass jar or ceramic vessel.
- Punch or drill a hole in the lid just large enough for the wick.
- Thread the wick through the hole, leaving 1 cm exposed above.
- Fill the reservoir with fuel and close the lid.
- The lid prevents spills and reduces evaporation.
A small jam jar with a hole punched through the metal lid is the fastest version.
The overview does not say what happens to the air space. As the wick draws fuel out, the fuel must be replaced by air. If the wick fills the hole so tightly that no air can pass, pressure falls, the feed slows and the flame dims while plenty of fuel remains. If the flame dims with fuel left, loosen the wick slightly so air can seep alongside it, or add a second small vent hole.
Method
Step 1: Prepare the lid. Punch the hole from the inside of the lid outward, so any burr faces away from the wick. File or bend down sharp edges.
Step 2: Thread the wick. It should slide with slight friction and reach the bottom of the jar.
Step 3: Fill to about three-quarters. Leave air space above the fuel.
Step 4: Soak and light. Let the wick fill with fuel first.
Worked Example
If the jar holds 240 ml (the cup size the overview uses) and you fill it to three-quarters, that is 0.75 × 240 = 180 ml. At 30 ml/h for vegetable oil, 180 ml ÷ 30 ml/h = 6 hours.
Common Mistakes
- Using kerosene. The lid and wick tube conduct heat into the fuel, and kerosene’s vapour collects in the sealed air space above it with a flame at the hole. Use fat or vegetable oil.
- Sealing the wick airtight. The flame dims with fuel left in the jar.
- Using a thin glass jar close to a large flame. Glass can crack; keep the flame small and the wick short.
Safety
A hot lid and trapped vapour
The metal lid gets hot enough to burn skin. Do not carry the lamp while lit and do not refill until it has cooled. If fuel ignites, cover with a lid or smother with dry sand or earth, never water. A smoking flame means incomplete burning and carbon monoxide, which cannot be seen or smelled; ventilate with an inlet and an outlet.
What’s Next
- Learn next: Tin Can Lamp — a sturdier version with a wick holder
- Combine with: Vegetable Oil — the right fuel for a lidded lamp