Candle wicks: types, choosing the diameter, care and flame safety

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The wick controls the flame, the smoke and the safety of a candle as much as the wax does. Wick types, how to choose and trim them, and what to know about lead and metals.

Key points

Common material	Braided cotton; sometimes paper, wood or synthetic fibres
Principle	Melted wax rises up the wick by capillary action and burns as vapour
Types	Flat, round, square, cored (paper, fibres, zinc), wooden
Recommended length before lighting	About 5 mm, trimmed each time
Metal banned in the United States since 2003	Lead (lead-cored wicks)
Common defects	Carbon mushroom, tall flame, tunnelling, soot
Point to watch	A wick unsuited to the wax or to the diameter makes the candle less safe

What the wick is for

It is the wax, not the wick itself, that burns. The flame melts the wax beneath it, which rises into the wick’s fibres by capillarity (like water in blotting paper), evaporates near the flame and burns as a gas. The wick is consumed slowly, at its tip. The wick’s diameter, braid and stiffness control how much wax rises, and therefore the height of the flame, the size of the melt pool and the amount of soot.

If the wick is too small, it melts only the centre of the wax: the candle “tunnels” and often goes out. If it is too large, the flame is tall, the wax gets very hot, the candle smokes and the container heats up strongly.

The main types of wick

Type	Description	Use
Flat braided wick	Braided cotton in a strip that bends towards the flame and trims itself	Slim candles, tapers
Square wick	Braided cotton with a square cross-section	Beeswax or plant wax candles
Round cored wick	Cotton around a core of paper or fibres	Candles in jars, more rigid
Zinc-cored wick	Braided cotton around a zinc or alloy wire	Candles in jars, stands upright
Wooden wick	Small wooden strip, sometimes crackling	Decorative candles; wide flame

Cotton wicks are often treated with salts (such as ammonium compounds) so that they do not keep glowing after the flame goes out.

Lead and metal-cored wicks

In the past, some wicks for candles in jars contained a lead wire to keep them upright. These wicks were criticised because burning could release lead vapours. In the United States, their manufacture, import and sale have been banned since October 2003; they have disappeared from most markets for several decades. Today’s metal-cored wicks mainly use zinc or a zinc alloy.

If you have doubts about an old candle or one of unknown origin (flea market, car boot sale), you can try a simple check: rub the wick on a sheet of white paper. A grey pencil-like mark indicates lead. This check is not official; when in doubt, do not light it. For any new product sold in France, product safety rules apply; see Our commitments.

Choosing the right wick

Jar diameter: the wider the candle, the stronger the wick must be (or several wicks). Manufacturers publish matching charts.
Type of wax: harder waxes (beeswax, paraffin) need sturdier wicks; plant waxes (soy, rapeseed) and scented oils also influence the choice.
Fragrance and dyes: they change how the candle burns, sometimes considerably; a heavily scented candle may need a different wick.
Testing: a reputable manufacturer tests the candle, with its wick, in its final jar. Otherwise, the result tells you: a steady flame, 1 to 3 cm high, wax melted across the full width after a few hours, little smoke.

Care: trimming, centring, extinguishing

Before each lighting, trim the wick to about 5 mm (some manufacturers say 6 mm) with scissors or pliers, and remove any carbon debris.
First burn: let the whole surface melt; a rule of thumb often cited is about one hour per centimetre or per inch of diameter, but follow the manufacturer’s instructions. Avoid relighting it for very short sessions.
Duration: manufacturers often advise not to burn for more than three to four hours at a stretch; there is no official figure.
Extinguishing: use a snuffer rather than blowing, which spatters hot wax; dip the wick into the melted wax, then straighten it.
End of use: stop when about one centimetre of wax remains in a jar (the glass can overheat and crack).

Common problems

Problem	Probable cause	Response
Black mushroom on the tip	Wick too long or too thick, or a rich fragrance	Extinguish, let cool, trim the head of the wick
Tall flame, soot	Wick too long, draught	Extinguish, trim to 5 mm, move the candle
Tunnel	Wick too small or first burn too short	Smooth the surface with a hairdryer, or replace the candle
Flame goes out	Wick drowned in wax, excess oil added	Pour off a little melted wax, centre the wick

For home fire safety, see Fire safety and rituals. The pollutants emitted by candles are limited by moderate use and ventilation (see Paraffin wax).

Frequently asked questions

How far should I trim the wick?

To about 5 mm before each lighting; some manufacturers recommend 6 mm.

Why does my candle produce soot?

Most often the wick is too long, or the flame is in a draught. Extinguish the candle, trim the wick and move the candle somewhere sheltered.

Are wooden wicks safer?

Not especially. They give a wider flame and a crackling sound; the same precautions apply.

Is there still lead in wicks?

Lead-cored wicks have been banned in the United States since 2003 and have become rare; today’s metal-cored wicks mainly use zinc. Be wary of old candles or those of unknown origin.

Can a drowned wick be fixed?

Yes: remove a little melted wax with absorbent paper, straighten the wick with pliers, and let the candle cool before relighting it.

Also read

HerbBeeswaxHard wax, stronger wick HerbSoy waxJar wax HerbParaffinMineral wax and emissions HerbFire safety and ritualsFire safety GlossaryIncense, Candles and Rituals GlossaryThe vocabulary of candles

The meanings mentioned belong to tradition and symbolism. They are neither promises of results nor medical advice. Back to Herbs, waxes and accessories.

Original illustration Oracle & Opale

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