The term "non-toxic candle" gets used loosely. It has no legal definition, no regulator enforcing it, and plenty of brands applying it to products that do not really deserve it. So what actually determines how clean a candle is? Four things: the wax, the wick, the fragrance and its load, and how you burn it. Each one matters. None of them alone is enough.

The wax: soy and plant waxes vs paraffin

Paraffin is a petroleum by-product. When it burns, it releases small amounts of volatile organic compounds including toluene and benzene. The quantities from a single candle in a ventilated room are low enough that most studies have not linked casual candle use to measurable health harm. Still, if you are burning candles regularly in a smaller space, it adds up. Paraffin also tends to produce more soot, which blackens walls and jar rims over time.

Soy wax, made from hydrogenated soybean oil, burns cooler and cleaner. It produces significantly less soot and no petrochemical emissions. The same is true of other plant-based waxes: rapeseed, coconut, and blended plant waxes all behave similarly. They are not perfect combustion, nothing is, but they are a meaningful step in the right direction.

This is why our soy candles use a natural soy wax base throughout. No paraffin, no blending in cheaper petroleum wax to cut costs. We are also vegan and cruelty-free, so beeswax is not something we use either.

The wick: cotton is standard, but it is worth checking

Lead-cored wicks were banned in the US in 2003 and have been out of common use in the UK for longer. But metal-cored wicks do still exist. Some manufacturers use zinc or tin cores to stiffen the wick, which helps it stay upright in certain wax types. These are generally considered safe at low levels, though the picture is less clear than with pure cotton.

A cotton wick, possibly with a paper core for structure, is what you want. It burns cleanly, curls naturally as it goes, and does not introduce any metal into the combustion. You can usually tell at a glance: a cotton wick looks soft and fibrous, a metal-cored wick has a stiffer spine you can feel if you pinch it before lighting.

Wick sizing matters too. A wick that is too large for the vessel will overheat the wax, produce excess soot, and burn hotter than it should. A well-made candle uses a wick sized for its specific diameter, wax type, and fragrance load. This is not just about performance; it is a safety and air-quality consideration.

All of our candles use natural cotton wicks. No metal cores, no exceptions.

The fragrance: this is where it gets complicated

Fragrance is where most of the nuance lives, and also where the most misleading claims appear. The argument you will often see is that essential oils are natural and therefore safe, while synthetic fragrance oils are chemical and therefore suspect. It is a tidy story. It is also wrong.

Many essential oils contain potent natural compounds that can be irritating or sensitising when inhaled in concentration. Linalool, limonene, eugenol, and cinnamaldehyde are all found in common essential oils, all flagged by IFRA (the International Fragrance Association) as compounds requiring use limits. The fact that they come from a plant does not change how they behave in a room at high concentrations. Neat essential oils poured into a candle at heavy loads can actually be more problematic than a well-formulated synthetic fragrance.

IFRA compliance is the standard worth looking for. IFRA sets industry limits on individual fragrance ingredients based on end-use category, burn rate, and exposure route. A fragrance oil that is IFRA-compliant for candles has been formulated to stay within those limits. That applies whether the ingredients are natural, synthetic, or both. Fragrance blends are often a mix, which is fine. The formulation and load matter far more than the natural/synthetic label.

Fragrance load matters too. Candles typically carry fragrance at between 6 and 12 per cent of the wax weight. Above that, unbound fragrance can pool on the surface, flare during lighting, or release uncombustion compounds. Responsible makers test their throw at realistic loads rather than simply chasing the strongest cold-throw in the jar.

We use IFRA-compliant fragrance oils across our range. Some contain natural isolates, some are blended, all sit within safe use limits for candles. We do not use high-concentration essential oils in our candles, and we do not overclaim on "100% natural fragrance" as a proxy for safety.

The container and how you burn it

The vessel matters more than people think. Glass is the standard for a reason: it is non-reactive, handles heat without off-gassing, and does not affect the chemistry of what is burning. Cheaper candles sometimes use thin or recycled glass that can crack under thermal stress. That is a safety issue, not just an aesthetic one.

Scented candles in tins are common and generally fine, though aluminium can get hot to the touch and the surface underneath should always be heat-safe. Avoid candles in decorative ceramic or concrete vessels unless you can confirm the glaze is non-reactive at high temperatures.

Beyond the vessel, burn habits make a real difference to air quality. A candle that is technically well-made can still fill a room with soot and volatile compounds if it is burned badly.

• Trim the wick to roughly 5mm before each burn. A long wick mushrooms and soots.
• Allow the wax to pool to the edge on the first burn. This prevents tunnelling and means the wick stays properly positioned.
• Burn in a ventilated room, not a completely sealed space. Fresh air in, stale air out.
• Do not burn for more than four hours at a stretch. Extended burns overheat the wax and can cause the wick to wander.
• Keep the flame away from draughts. A flickering candle burns inconsistently and throws more soot.

Our 30cl single-wick candles are designed for a burn time of around 35 to 45 hours. The 60cl three-wick is the larger format, intended for bigger rooms and longer evenings. Both are hand-poured in Glasgow, in glass vessels sized for the wax and wick combination we use.

Common questions

Are soy candles non-toxic?

Soy candles are a cleaner choice than paraffin, producing less soot and no petrochemical emissions. But "non-toxic" depends on the whole candle, including the wick, the fragrance, and the load. Soy wax is a good starting point, not a guarantee on its own.

Do candles release chemicals when burned?

All candles release some compounds during combustion, including carbon dioxide, water vapour, and trace volatile organics. The type and quantity vary significantly by wax, fragrance, and wick. Soy candles with IFRA-compliant fragrances and cotton wicks produce far fewer of concern than paraffin candles with synthetic fragrance at high loads. Good ventilation, a trimmed wick, and sensible burn times reduce exposure further.

Are essential oil candles safer than synthetic fragrance candles?

Not automatically. Essential oils are not inherently safer than synthetic fragrance oils, and at high concentrations some are more sensitising. What matters is IFRA compliance, fragrance load, and formulation, not whether the scent ingredients come from a plant or a lab.

What makes clean home fragrance different from regular fragrance?

There is no regulated definition of "clean" in home fragrance. As a useful shorthand, look for: plant-based wax, cotton wicks, IFRA-compliant fragrance at sensible loads, no phthalates listed in the ingredients, and honest burn testing. Transparency about what is in a product matters more than the marketing label on the outside.

If you want to go further, our approach to making covers how we source, test, and hand-pour here in Glasgow. And if candles are new to you, the full soy candle range is a good place to start looking.