Why is my candle smoking black? 5 common reasons

Seeing black smoke coming from a candle can be worrying. Many people immediately think of a quality defect, whereas in most cases, the black smoke is related to the use of the candle, and not to the candle itself .

Here are the 6 main causes , scientifically known, and how to remedy them.

1. The strand is too long

This is the most common cause of black smoke.
A lock of hair that is too long results in:

• a flame that was too high
• incomplete combustion
• the formation of soot (unburned carbon particles)

👉 Ideal length : approximately 5 mm before each ignition.

📌 Verifiable fact: a stable flame should measure approximately 2 to 3 cm . Beyond that, combustion becomes unstable.

Solution
Always trim the wick before lighting your candle, using a wick trimmer or clean scissors.

2. The candle is exposed to a draft.

An air current disrupts the flow of oxygen to the flame, causing:

• a flickering flame
• incomplete combustion
• black smoke

Common sources:

• windows half-open
• kitchen hood
• ventilation
• repeated passing nearby

Solution
Always place your candle in a quiet and stable location, away from air currents.

3. The wick or wax is not suitable

Not all wicks are suitable for all waxes.
An incorrectly sized drill bit can:

• burn too fast
• create an excess of carbon
• produce soot

Well-formulated handcrafted candles use:

• untreated cotton or wood wicks
• precise calibration according to the diameter of the container
• a suitable wax (soy, rapeseed, olive…)

📌 Established fact: an oversized wick produces more carbon than it can burn → black smoke.

4. The first combustion was poorly executed.

The first combustion determines the "memory" of the wax.
If the candle is extinguished too soon:

• the wax melts unevenly
• The wick is not getting enough power.
• The flame becomes unstable → smoke

📌 Physical principle: the wax must melt to the edge to ensure even combustion.

6. The overall quality of the candle

Low-end industrial candles sometimes use:

• highly refined paraffin waxes
• chemically treated strands
• perfumes not heat-stabilized

These factors increase the risk of soot.

Well-made, handcrafted candles prioritize:

• vegetable waxes
• untreated strands
• perfumes tested in actual combustion

How to avoid black smoke? (summary)

✔ Trim the wick before each lighting
✔ Avoid drafts
✔ Respect the combustion time
✔ Choose a candle that is appropriate for the size of the room
✔ Favoring controlled artisanal manufacturing