The best lamp wick is 100% cotton, either a strip of cloth 1 to 2 cm wide cut from an old t-shirt or sheet, or several strands of cotton string twisted or braided together. Jute and hemp cord work but smoke more, milkweed floss and cattail fluff burn fast and suit only emergencies, and synthetic fabric must be avoided because it melts.
Part of Oil Lamp Construction
Cotton is the preferred wick fibre because it absorbs fuel well and burns steadily, while coarser plant fibres smoke more and synthetics melt. Finer fibre lifts fuel higher but delivers it more slowly.
Cotton Wins Because It Is Absorbent And Burns Steadily
The oil-lamp overview ranks wick materials:
- Cotton fabric strips — the best option. Cut from old t-shirts, sheets or any 100% cotton fabric, 1 to 2 cm wide.
- Cotton string or twine — several strands twisted or braided together.
- Jute or hemp cord — works, but smokes more than cotton.
- Milkweed floss or cattail fluff — functional but burns fast; emergency use.
- Rolled paper — works briefly, then chars and crumbles.
- Synthetics and blends — do not use. They melt, do not wick properly and give off toxic fumes.
Fine Fibres Lift Fuel Higher But Deliver It More Slowly
The height a liquid climbs in a narrow gap is given by Jurin’s law, h = 2γ cosθ ÷ (ρ g r), where γ is surface tension, θ the contact angle (close to zero for a liquid that wets the fibre, so cosθ ≈ 1), ρ the density, g = 9.81 m/s² and r the radius of the gap.
Worked example (idealised). For olive oil take γ ≈ 0.032 N/m and ρ ≈ 915 kg/m³ (typical handbook values), and assume gaps of radius 50 µm (5 × 10⁻⁵ m):
h = 2 × 0.032 ÷ (915 × 9.81 × 5 × 10⁻⁵) = 0.064 ÷ 0.449 ≈ 0.14 m, about 14 cm.
For a tighter 10 µm gap (10⁻⁵ m) the same formula gives about 0.71 m, five times higher. The gap radius is an assumption, not a measurement of any real wick. The lesson is the direction: tight fibre lifts higher, but a tight gap also resists flow, so a fine wick feeds a flame slowly. Molten fat is thicker than kerosene and flows more slowly through the same wick, so a fat lamp usually wants a looser or wider wick than a kerosene lamp.
It also explains why a lamp burns dim as its reservoir empties: the lower the fuel, the further it has to climb.
Method: Cutting And Preparing Cotton
Step 1: Cut. Cut 100% cotton cloth into strips 1 to 2 cm wide, in a length that reaches from the reservoir bottom to just above the holder.
Step 2: Check. Stand one end in your fuel. The fuel should visibly climb the strip.
Step 3: Seat. Thread it through the holder snugly enough to stay put, loosely enough to slide when you adjust the flame.
Step 4: Soak, then light. Let fuel climb the whole exposed length before lighting.
Common Mistakes
- Using dyed or flame-retardant cloth. Avoid fabric labelled flame-retardant; it resists burning.
- Making the strip too tight in the holder. A wick that cannot move fuel starves the flame.
- Trusting milkweed or cattail fluff for a night’s light. It burns fast; use it only to get through an emergency.
Safety
Fumes and soot
Synthetic blends release toxic fumes when melted. A smoking cotton wick is too high or untrimmed; lower it. Soot is incomplete burning and incomplete burning makes carbon monoxide, which has no smell; a headache or drowsiness near a smoking lamp is a reason to ventilate and get into fresh air, not to rest.
What’s Next
- Learn next: Wick Sizing & Brightness — choosing the strip width
- Combine with: Braided vs Twisted Wicks — turning strands into a cord