Every week someone tells Glow their candle is leaving black marks up the inside of the jar. Nine times out of ten, the wick has grown too long. A candle wick trimmer is the fix, and it takes five seconds before you strike a match.

Why a candle wick trimmer matters more than scissors

A long wick bends over as it burns. The flame licks the side of the glass instead of staying centred, and soot, the black flecks you see drifting up, forms. The National Candle Association explains that a clean flame burns in a "quiet teardrop shape." Soot is what you get when that shape breaks down.

Kitchen scissors leave a jagged, angled cut. A candle wick trimmer sits flat on the rim of the jar. It cuts straight across. That is why it beats anything else in the drawer.

Why does my candle leave black marks on the glass?

The wick has grown past its ideal length, so the flame flares and smokes. Trim it to about 5mm before every burn with a wick trimmer from the candle care range and the marks stop.

The right way to use a wick trimmer for candles

A wick trimmer for candles is built to reach into a deep jar without dropping ash into the wax. Trim before the first burn and before every burn after that, not just when you remember. A trimmed wick helps the wax melt evenly across the top. That gives a jar candle its full scent throw, how far the fragrance actually spreads through a room.

Twenty-five years of watching what comes back through our ambassador network taught us this. Almost every complaint about a "faulty" candle traces back to an untrimmed wick, not the wax or the fragrance oil.

• Trim to 5mm before lighting, every time
• Keep candles 8cm apart when burning more than one
• Let a new candle burn until the wax melts edge to edge

A candle care kit covers the rest

A full candle care kit adds a snuffer and a lighter to the trimmer. You are never blowing out a floral jar and scattering wax droplets across the sideboard. If your favourite is a soft floral candle, a jasmine candle is a good one to practise on. Its lighter wax shows soot marks fastest, so the habit sticks quickest.

Quick answers

How often should you trim a candle wick?

Before every single burn, not just occasionally. A wick left untrimmed for two or three burns grows long enough to flare, smoke and shorten the candle's life.

Is candle soot bad for you?

Soot is unburned carbon from an uneven flame, in any candle, any wax. Keeping the wick trimmed and the room ventilated keeps the flame burning clean, which is the standard safety advice.

None of this needs a special trip to the shops. A trimmer lives in most Glow accessories orders already, tucked in beside the candle. Add one next time you top up your favourite jar.

Related reading

• Essential Care Tips for Your High Quality Scented Jar Candles: the fuller care routine this trimming habit fits into.
• What To Do With The Last Bit Of Wax In A Candle Jar: what changes once the wax pool gets low.
• What Makes A Candle Sustainable, And How To Check: how a full, even burn also cuts waste.