Why Wick Size Deserves More of Your Attention

Of all the variables in a handmade container candle — wax blend, fragrance load, dye, pouring temperature, cure time — the wick is the one that most often decides whether the finished candle performs beautifully or sulks at the back of the shelf. Too small and the flame drowns in its own melt pool, leaving a stubborn ring of unburnt wax around the glass. Too large and you get an overheated jar, a smoky flame and a wick that mushrooms into a little cauliflower by the second burn.

Wick charts are a starting point, not a verdict. The recommended size for a given jar diameter is the first candidate in a series of tests, not the answer. The encouraging news is that wick testing is cheap, quick to learn and strangely satisfying once you know what you are looking at.

Measure the Inside Diameter, Not the Label

Begin with the widest inside diameter of the container, measured in millimetres at the level where the wax surface sits. The outside measurement is irrelevant — a thick-walled tumbler can be 10mm wider externally than the wax it actually holds. For a tapered jar, measure at the widest internal point, usually just below the rim, because that is where the melt pool must reach.

As a rough starting point for a soy or soy-blend wax in a room at around 20°C:

• 50–60mm: the smallest single wick in your chosen series
• 60–70mm: a mid-range single wick
• 70–80mm: the largest single wick you will comfortably run, or consider two smaller ones
• Over 80mm: two or three wicks, spaced evenly, each sized for its own section of the jar

Treat these as launch points for soy only. Every other wax will shift the number, and the only way to confirm is to burn a test candle.

Wax Blends, Fragrance and Colour All Move the Number

Wicks are matched to how a wax melts and how thick the resulting pool becomes. The harder the wax works to melt, the more heat you need at the flame, which means a larger wick.

• Paraffin melts readily and generally takes a smaller wick than soy in the same jar.
• Soy and soy blends are denser and slower to melt, usually needing one size up from paraffin.
• Coconut and coconut-soy blends sit between the two, often burning cleanly with a slightly smaller wick than pure soy.
• Beeswax and beeswax blends have a high melt point and can need two sizes up, sometimes more.
• Stearic acid and other hardeners raise the melt point and demand extra heat.

Fragrance is the other big lever. At a 6–10% load, expect to wick up one size compared with an unscented candle. Heavy, resinous or vanilla-rich oils are the thirstiest, and dark dyes add pigment particles that also slow the melt. A jar with 10% fragrance and a deep colour can need two sizes more than the same jar left plain. Pour temperature, cure time and the ambient temperature of the room you burn in all nudge the result too — a candle tested in a chilly workshop will behave differently in a warm living room.

Choose One Wick Series and Learn Its Language

Wick numbers are not transferable between series. An "8" in one family is not the same as an "8" in another; flame height, curl, coating and core all differ. Pick a series suited to your wax — flat braided cotton is a dependable choice for soy, while paper-cored and knitted wicks behave differently again — and then learn that series thoroughly.

Also note the hardware. A wick tab lifts the base of the wick above the floor of the jar, and the height of the tab changes how much exposed wick you get. Trim to about 5mm before every single burn. Centring matters more than most makers expect: a wick 2mm off centre will tunnel on one side no matter how well it is sized, so use a wick bar or steadying clip while the wax sets.

How to Run a Burn Test That Tells You Something

A burn test is only useful if it is repeatable. Keep the conditions steady and change one thing at a time.

• Cure properly: 24–48 hours for paraffin, one to two weeks for soy blends.
• Control the room: 20–22°C, still air, away from radiators, windows and extractor fans.
• Burn in sessions of two to four hours. Aim for a full melt pool reaching the glass within roughly an hour per 25mm of diameter.
• Cool completely and trim to 5mm between sessions.
• Test two adjacent sizes side by side in identical jars so you have a genuine comparison, not a memory.
• Burn all the way down to within 10mm of the base. A wick that performs at the top can still misbehave at the bottom.

Write down the jar, wax, fragrance percentage, dye, wick series and size, room temperature, burn times and what you observed. That notebook becomes more valuable than any chart.

Reading the Signs: Tunnelling, Soot and Other Clues

• Wax clinging to the walls, a wick that keeps drowning, a flame that struggles or goes out: the wick is too small. Widen one size.
• Soot on the glass, a tall flickering flame, a jar too hot to touch, heavy mushrooming: the wick is too large. Drop one size.
• A clean first burn that tunnels afterwards: usually the first burn was cut short, or the room was cold. Remove the wax memory by burning longer next time before blaming the wick.
• An even first burn that turns sooty halfway down: the jar is warming as the candle shortens, so the wick is now oversized. This is common and is one reason mid-range sizes often outperform the extremes.

Sizing a wick is a small, patient craft in its own right, and the makers who get it right are simply the ones who tested rather than guessed. Buy a few sizes around your best estimate, keep your conditions steady, and let the notebook do the remembering. The candle that burns edge to edge with a calm, steady flame is the reward — and it will be entirely your own work.