The wick decides how a candle burns more than anything else in it. Too small and the candle tunnels down the middle, wasting the wax around the edge and smothering the scent. Too big and it smokes, soots up the jar and gets the glass dangerously hot. This guide covers the wick types, how to pick a size for your container and wax, how to run a test burn, and what the finished candle is telling you when something goes wrong.
Types of candle wick
- Cotton wicks are the standard for container candles. They burn cleanly with a steady flame and suit soy, paraffin, palm and blended waxes. With no stiffening core they are a little soft, so they need centring and holding upright while the wax sets. Ours are pure cotton, pre-waxed, in 12, 15 and 20 cm.
- Cotton and paper wicks have a paper thread woven into the cotton. The paper stiffens the wick so it stands up on its own while you pour, and gives a steadier flame with less soot. A good choice for beginners and for soy wax. See our cotton and paper interwoven wicks.
- Wooden wicks are flat strips of wood in a metal clip. They crackle softly as they burn and open a wider melt pool than a cotton wick of the same size. For wide containers, two wooden wicks in one clip is the usual arrangement.
Pre-waxed (primed) wicks, like all of ours, burn more evenly from the first light than raw braided cotton. You can see the full range in our candle wicks collection.
How to choose the right wick
Start with the container's diameter
The width of the container matters far more than its height. A wick has to melt the wax all the way to the edge, so a wider jar needs a larger wick, or more than one. As a rough rule, once a container is wider than about 8 to 10 cm, a single wick will struggle to melt to the edge, and two or three evenly spaced wicks work better. Always confirm with a test burn.
Pick a wick longer than the container is tall
Choose a length that stands 1 to 2 cm above the finished wax, so you have enough to hold while centring it and to trim later. For a jar 10 cm tall, a 12 cm wick is about right; for 13 to 18 cm, use 15 or 20 cm.
Allow for the wax
- Soy wax is dense and has a lower melt point, but it is harder for a flame to pull through. Soy candles usually need a slightly larger wick than the same candle in paraffin. Our NatureWax C-3 soy wax is made for containers.
- Beeswax has a high melt point and a thick, sticky melt, so it usually needs a larger wick again. See our refined white beeswax pellets.
- Paraffin and blends burn most freely and can take a smaller wick.
Allow for fragrance and colour
Fragrance oils and dyes change how a candle burns. A high fragrance load, or heavy, sweet oils such as vanilla, can clog a wick and make it mushroom. If you change the fragrance or its percentage, test the wick again. How much fragrance each oil can safely take in a candle is in the usage table on its product page, among our perfume oils.
Setting the wick
- Fix the wick tab to the centre of the empty container with a wick sticker, pressing it down firmly.
- Straighten the wick and hold it upright with a centring bar across the mouth of the jar. An off-centre wick is the most common cause of a candle tunnelling down one side.
- Pour, let the candle cure (soy wax improves over one to two weeks), then trim the wick to about 5 to 6 mm before lighting.
How to run a test burn
There is no chart that replaces testing, because every combination of container, wax, fragrance and dye burns differently. Make two or three test candles with different wick sizes and burn them side by side.
- Label each candle with the date, wax, fragrance and percentage, and wick. Keep notes: when a design works, you want to know exactly why.
- Weigh each candle before and after every burn. The weight lost per hour shows how hard the wick is working, and a candle burning much faster than the others is running hot.
- Burn in sessions of about three to four hours, away from draughts. Check every hour: the flame height, the width of the melt pool and any smoke.
- Look at the first burn closely. The melt pool should reach, or nearly reach, the edge of the container within about three to four hours. If it doesn't, the wick is too small.
- Keep going to the bottom. A wick that is right at the top can run too hot in the last third, where heat builds up in the glass. Test through several burns, right down to the end.
Reading the results
| What you see | What it usually means |
|---|---|
| A hole down the middle with a wall of unmelted wax | Wick too small, or the first burn was too short. See candle tunnelling. |
| A carbon "mushroom" on the tip of the wick | Wick too large, too much fragrance, or the wick needs trimming |
| Black soot on the glass or a flickering, smoking flame | Wick too large or not trimmed, or a draught |
| A very deep melt pool or a glass too hot to touch | Wick too large. Go down a size. |
| Weak scent when lit, although it smells fine cold | Often a wick too small to build a full melt pool |
| A flame that drowns and goes out | Wick too small for the wax, or clogged by fragrance or dye |
Save a candle without starting again
If a finished test candle has the wrong wick, you don't always need to pour a new one. Remove the old wick with a straw or an apple corer, set a new wick in the hole and fill it with melted wax of the same batch. It is fine for testing, but for candles you sell, start again with the right wick.
Once the wick is right, the next thing to get right is the pour. Our guides to why candles crack and making your first scented candle cover the rest. Everything you need is in our candle making collection.