Cotton wick. Source: Wikimedia Commons (CC BY-SA 3.0)
The wick is the component that most directly controls how a candle burns. An incorrectly sized wick causes two distinct failure modes: tunnelling (burning a narrow channel through the centre, leaving wax on the walls) or mushrooming and soot (excessive flame size producing carbon deposits). Neither is immediately obvious until several burn cycles have been completed, which is why wick testing requires patience and systematic record-keeping.
How wick sizing works
Wick manufacturers produce wicks in numbered series — the specific numbering varies by brand (ECO, CD, LX, and Wooden are the most common series). Within each series, a higher number indicates a larger wick diameter and greater fuel draw. The correct size depends on:
- Vessel inner diameter: The most direct variable. A larger diameter requires more heat to achieve a full melt pool.
- Wax type: Harder waxes (beeswax) require more heat than soft waxes (coconut). Denser waxes need a larger wick to maintain an adequate melt pool.
- Fragrance load: Higher fragrance percentages increase the combustible material in the melt pool and may require a slightly smaller wick to avoid oversized flames.
- Dye content: Dyes can affect burn rate; undyed candles often need a slightly smaller wick than the same formula with dye.
Wick types and their characteristics
Cotton core wicks (ECO, CD series)
Cotton wicks are the most common choice for container candles with natural wax. They are available pre-tabbed (with a small metal sustainer at the base) and in continuous spools. ECO wicks have a slightly stiffer structure that helps them stay centred during pouring and maintains vertical orientation through the burn. CD wicks are flat-braided and tend to have a lower mushrooming rate.
LX wicks
LX wicks are flat cotton wicks that curl slightly during burning, which reduces carbon buildup. They are frequently recommended for soy wax and soy-coconut blends. Their self-trimming behaviour can reduce the need for manual trimming between burns, though some mushrooming still occurs at higher fragrance loads.
Wooden wicks
Single-ply and double-ply wooden wicks produce a crackling sound during burning and a wide, low flame profile. They are more sensitive to fragrance load and wax density than cotton wicks. At high fragrance concentrations (above 8%), wooden wicks frequently self-extinguish. They work best with coconut wax or coconut-soy blends at fragrance loads of 6% or below.
Hemp wicks
Hemp wicks produce more soot than cotton at equivalent sizes and are less commonly used in craft candle production. They appear occasionally in artisan markets in Poland but are not standard for container candles.
Wick sizing reference
The following table provides starting points for wick selection. These are initial test sizes — burn testing and adjustment is always required.
| Vessel diameter (inner) | Soy wax (container grade) | Beeswax (pure) | Soy/Coconut blend (70/30) |
|---|---|---|---|
| Up to 50mm | ECO-2 or CD-10 | ECO-4 | LX-14 or ECO-2 |
| 51–65mm | ECO-4 or CD-12 | ECO-6 | LX-18 or ECO-4 |
| 66–80mm | ECO-6 or CD-14 | ECO-8 | LX-22 or ECO-6 |
| 81–100mm | ECO-10 or CD-18 | ECO-12 | LX-26 or ECO-10 |
| Over 100mm | ECO-14 or dual wick | ECO-14 or dual wick | Dual LX-22 |
These sizes are starting points for 8% fragrance load in undyed wax. Adjust one size up for heavy fragrance loads (above 10%), dyed candles, or ambient temperatures consistently below 18°C. Adjust one size down for fragrance loads below 5%.
The testing process
Wick testing cannot be reliably skipped. A single burn test does not produce enough data — the first burn establishes the melt pool diameter and the trim requirement, subsequent burns reveal whether the melt pool deepens correctly and whether the wick self-centres.
What to observe during testing
- Melt pool diameter after the first two hours of burning: For container candles, the melt pool should reach the container wall within two to four hours of the first burn. A melt pool that stops short of the wall after four hours indicates the wick is too small.
- Flame height: A steady flame between 2cm and 3cm is generally acceptable. A flame consistently above 4cm suggests the wick is too large.
- Mushrooming: Carbon buildup on the wick tip. Some buildup is normal after a two-hour burn. Excessive mushrooming (larger than 5mm) suggests the wick is too large or the fragrance load is too high.
- Soot: Black deposits on the inside of the vessel above the melt pool line indicate incomplete combustion. This is most often caused by an oversized wick or draughts.
Record-keeping
Systematic burn testing requires noting the wax type and batch, wick series and size, fragrance oil and load percentage, vessel type and inner diameter, ambient temperature, pour temperature, and the results of each burn session. Without records, test results cannot be reproduced when scaling.
Trimming
Wicks should be trimmed to approximately 6mm before each burn. Longer wicks produce taller flames and more mushrooming. Wick trimmers with a flat catch basin are available from most candle supply distributors and are more precise than scissors for consistent trimming.
Wick sizes listed in this article are reference starting points only. All wick selections must be tested with the specific wax, fragrance, and vessel combination before production. Candle making involves open flame — follow appropriate fire safety practices at all times.
Updated: June 2026 · References: Wikipedia — Candle wick