The wick you choose has more impact on how your candle performs than any other single component — more than the wax, the fragrance, or the container. Get the wick right and your candle burns evenly, throws scent well, and lasts for hours. Get it wrong and you end up with tunnelling, smoking, drowning wicks, or dangerously large flames.
This guide covers the main wick types available for soy wax candles in the UK, how to pick the right size for your container, and how to test your way to a clean burn.
Why Wick Choice Matters So Much
A candle wick is not just a piece of string that carries a flame. The wick controls the size of the melt pool (the liquid wax that forms as the candle burns), which in turn determines how much fragrance is released and whether the candle burns evenly across the full diameter of the container.
If the wick is too small, the melt pool will not reach the edges of the jar, causing tunnelling — that frustrating ring of solid wax around the outside that never melts. If the wick is too large, the flame will be too hot, the candle will burn through wax too quickly, and you will see black soot collecting on the jar walls.
Cotton Wicks (ECO and CD Series)
Flat-braided cotton wicks are the most popular choice for soy candle makers. The two main series you will find on Amazon UK are the ECO series and the CD series.
ECO wicks are made from natural cotton with a thin paper thread woven through the braid. This paper filament causes the wick to curl slightly as it burns, which keeps the flame self-trimming and reduces the mushrooming (carbon buildup) that you see on straight wicks. ECO wicks burn at a moderate temperature and work well with soy wax at standard fragrance loads (6-10%).
CD wicks have a similar cotton construction but are designed to burn slightly hotter. They are a better match for heavily fragranced candles or candles with additives like dyes that can clog cooler-burning wicks. If your ECO wick is tunnelling despite being the right diameter, stepping up to a CD wick of the same size often solves the problem.
Wooden Wicks
Wooden wicks have surged in popularity over the past few years, largely thanks to the gentle crackling sound they produce — like a miniature fireplace. They create a wider, shorter flame compared to cotton wicks and look distinctive in a finished candle.
Wooden wicks work well in soy wax but require some adjustment to your process. They need to be trimmed shorter than cotton wicks — about 3-4mm — and they perform best in containers where the wick width is roughly half the jar diameter. The main challenge is that wooden wicks can be inconsistent; grain patterns in the wood mean no two wicks burn identically, so you may need to test more samples to find reliable performance.
How to Size Your Wick
Wick sizing depends primarily on the diameter of your container. Most wick suppliers provide sizing charts, but these are starting points rather than guaranteed answers — you will still need to test.
As a rough guide for soy wax container candles: containers up to 5cm diameter work with small wicks (ECO 2 or ECO 4). Containers 6-8cm suit medium wicks (ECO 6 to ECO 10). Containers 8-10cm need larger wicks (ECO 12 to ECO 14). Anything wider than 10cm typically needs multiple wicks.
These are approximations. Your exact fragrance load, dye usage, and pouring temperature all influence how the wick performs. The only way to know for certain is to run burn tests.
How to Run a Burn Test
A proper burn test takes time but saves you from selling candles that perform poorly. Here is the process:
Make three identical candles using the same wax, fragrance, and container, but with three different wick sizes — one size down, your best guess, and one size up. Let all three cure for the same amount of time (at least one week, ideally two).
Burn each candle for 4 hours at a time. After each burn session, check the melt pool depth and diameter. The ideal melt pool reaches the edges of the container within 2-3 hours and is roughly 1cm deep. Note any smoking, mushrooming, or soot on the glass.
The right wick is the one that produces a full melt pool without excess smoking. If you are between sizes, go with the slightly larger option — a wick that is marginally too big is easier to manage (just trim shorter) than one that tunnels.
Common Wick Problems and Fixes
Tunnelling: Your wick is too small. Size up, or switch from ECO to CD for a hotter burn. Also make sure you are burning long enough on the first use — the first burn should last until the melt pool reaches the edges, even if it takes 3-4 hours. Read our beginner guide for more on getting the first burn right.
Mushrooming: Carbon buildup at the tip of the wick. Usually means the wick is slightly too large or the fragrance load is high. Trim more aggressively before each burn.
Smoking/sooting: Wick too large, wick too long, or drafts. Trim to 5mm and keep candles away from open windows and fans. Check our wax comparison guide — some waxes soot more than others.
Drowning wick: The wick is consumed faster than it can draw up wax, causing the flame to shrink and eventually extinguish. This happens when the wick is too small for the wax pool depth. Size up or reduce the container diameter. Browse our wick selection for pre-tabbed options in multiple sizes.
