Common mistakes when making candles
The four most common problems in candle making — frosting, tunnelling, mismanaged flashpoint and the difference between hot throw and cold throw — have specific causes and specific fixes that depend on the type of wax, the wick and the pouring process.
Frosting: a whitish, rough layer that appears on the surface of soy wax candles after cooling. It's a natural feature of plant wax, not a manufacturing defect. Soy wax has a crystalline structure that, when it solidifies slowly, tends to reorganise on the surface into visible patterns.
Frosting: Why It Appears and How to Reduce It
Frosting is the problem that causes the most confusion among people starting out with soy candles, mainly because it shows up after the candle already looks finished. The candle comes out of the mould or container looking good, and hours or days later the surface develops that opaque, rough layer that looks like a defect.
It isn't. Frosting is soy wax expressing its natural structure. Soy wax solidifies with a tendency to crystallise that other waxes don't have in the same way. The more natural the soy wax, the more pronounced the frosting — and the more you manipulate the cooling process to speed it up or slow it down, the more variable the result.
The variables that most influence the intensity of frosting are the pouring temperature, the temperature of the container, and the cooling speed. A pouring temperature that's too high produces slower cooling and more pronounced frosting. A cold container in a cold room speeds up surface cooling but can pull the wax away from the walls. The balance depends on the specific type of wax — the supplier's specifications are the right starting point, not a generic temperature.
The maker who tries to eliminate frosting completely on a 100% natural soy wax usually ends up frustrated, because you can't remove it entirely without changing the type of wax. Blended soy waxes — soy mixed with paraffin or coconut wax — show less frosting because the crystalline structure of the soy is interrupted by the other material. If a frosting-free look is a requirement, the right solution is to choose a wax suited to that result, not to keep adjusting the process indefinitely with a wax that will always produce it.
For anyone who wants to reduce it without changing wax: pouring at a lower temperature within the supplier's recommended range, warming the container slightly before pouring, and protecting the candle from draughts during cooling all reduce the intensity of frosting, though they don't eliminate it.
Tunnelling: The First Burn Decides Everything
Tunnelling is the problem that most affects a candle's lifespan and the one you can most directly prevent without changing materials.
Tunnelling is the burn pattern where the flame creates a vertical tunnel down through the centre of the candle without consuming the wax at the edges. The result is a candle that looks intact on the outside but has an ever-deepening central hole, with a significant amount of wax that never burns.
The main cause is the first burn. In a melted-wax candle, the first burn sets the memory of the wax pool: the pool of liquid wax that forms around the flame during that first session defines the diameter the candle will try to burn to in every later session. If the first burn is interrupted before the pool reaches the edges of the container, all later burns will follow that reduced pattern, leaving a wall of unburnt wax around the tunnel.
Prevention is direct: the first time you light a new candle, let it burn until the wax pool reaches or comes close to the edges of the container. The time needed depends on the diameter of the container and the type of wax — for an 8 cm diameter container it can be between two and four hours. Putting it out before that happens produces tunnelling in 90% of cases.
If tunnelling has already happened, there are techniques to try to correct it — warming the surface with hot air to level the wax, or wrapping the container in aluminium foil so the heat concentrates towards the edges — but none guarantees full recovery of the candle. Prevention on the first burn is always more effective than later correction.
The second factor that contributes to tunnelling is wick choice. A wick that's too thin for the diameter of the container produces a small flame that doesn't generate enough heat to melt the wax to the edges, even if the first burn is long. The right wick size for each container diameter is the variable to check before the first burn, not after the tunnelling appears.
Flashpoint and Fragrance Temperature
Flashpoint is the least visible problem during the making process but one of the ones that most affects the final result of the candle, both in terms of safety and scent quality.
The flashpoint of a fragrance is the temperature at which that substance releases enough vapour to ignite momentarily if an ignition source is applied. In candle making, the relevant flashpoint is that of the fragrance added to the melted wax.
The practical implication is this: if the fragrance is added to the wax while the wax is above the flashpoint of that fragrance, some of the most volatile aromatic components evaporate at the moment of mixing, before the candle solidifies. The result is a candle with less scent intensity than expected, or in extreme cases a visible reaction — smoke, spitting, or a burnt smell during mixing that tells you the fragrance is degrading.
The most common mistake here isn't being unaware of the concept — it's not checking the specific flashpoint of the fragrance you're using. Each fragrance has its own flashpoint, and generic instructions to 'add at X degrees' aren't reliable if you change fragrance without checking. The fragrance supplier should state the flashpoint. If they don't, it's information to ask for before producing.
On safety: working with fragrances near or above their flashpoint doesn't necessarily create an immediate fire risk under normal production conditions, but it does increase the risk if there are ignition sources nearby. The standard recommendation is to add the fragrance once the wax has cooled below the flashpoint of that specific fragrance, verified on the product's technical sheet.
Hot Throw and Cold Throw: Two Different Variables
The difference between hot throw and cold throw is one of the things that most confuses people starting to work with fragrances in candles.
Cold throw is the scent intensity a candle releases when it's unlit and at room temperature — what you notice when you bring your nose close without lighting it. Hot throw is the scent intensity while it burns, produced by the evaporation of the fragrance in the hot wax pool.
A candle can have an intense cold throw and a weak hot throw, or the other way round. Cold throw depends mainly on the amount of fragrance added and the affinity of that fragrance with the type of wax. Hot throw depends on the temperature of the wax pool, the wick size (which determines how much wax melts per hour), and the volatility of the fragrance's components at that temperature.
The most common mistake is adjusting the amount of fragrance to improve the cold throw without understanding that the hot throw can still be weak if the wick size doesn't generate enough heat. In that case, more fragrance doesn't solve the problem — it changes the symptom without touching the cause.
The variables to adjust for a better hot throw are the wick size (a thicker wick generates more heat and evaporates more fragrance per hour), the type of fragrance (some aromatic compounds evaporate at lower temperatures and work better in lower-heat candles) and the type of wax (soy wax has a lower pool temperature than paraffin, which can mean fragrances with high flashpoints have a weaker hot throw in soy than in paraffin).
Operational Scenario
A maker who had spent six months making soy candles to sell at local markets received three returns in one month with the same comment: the candle doesn't smell when burning. The cold throw in the photos was what had driven her sales — the candle smelled good on the stand — but the hot throw didn't match.
Reviewing the process, she identified two variables she had changed at the same time three months earlier: she had switched to a wider container (from 7 to 10 cm in diameter) and reduced the amount of fragrance by 20% to manage costs. The change in diameter required a thicker wick — which she hadn't adjusted. The result: a wick too thin for the container, a wax pool at a lower-than-optimal temperature, and a fragrance that didn't evaporate with enough intensity.
The fix was to recalibrate the wick for the new diameter and return the fragrance ratio to the previous level. The hot throw was back to the right level in the next batch.
The lesson: when you change the diameter of the container, the wick always needs recalibrating. Changing the container without adjusting the wick changes every combustion variable and can affect the hot throw, the tunnelling and the candle's lifespan all at the same time.
FAQ
Is frosting on soy candles a manufacturing defect? No. Frosting is a natural feature of soy wax — a consequence of its crystalline structure as it solidifies. It appears especially in high-purity soy waxes with no blends. You reduce its intensity by adjusting the pouring temperature and the cooling environment, but it doesn't disappear completely with 100% natural soy wax. If a frosting-free look is a requirement, the solution is a blended wax (soy with coconut or paraffin) rather than endless process adjustments.
What happens if you don't respect a candle's first burn? If you put it out before the wax pool reaches the edges of the container, the candle tends to develop tunnelling on later burns: a consumed central area and walls of unmelted wax. The first burn sets the pool memory. For medium and large containers, that can mean keeping the candle lit for between two and four hours in the first session.
How do I know if I'm adding the fragrance at the right temperature? By checking the flashpoint of your specific fragrance on the supplier's technical sheet. The temperature at which you add the fragrance should be below that flashpoint. There's no universal number valid for every fragrance — each one has its own. If the fragrance smokes, bubbles or smells burnt as you mix it, the wax was too hot.
Why does my candle smell good unlit but barely smell when burning? Cold throw and hot throw are different variables. An intense cold throw doesn't guarantee an equivalent hot throw. The factors that most affect hot throw are the wick size (which determines the pool temperature), the temperature of that pool, and the volatility of the fragrance at that temperature. If the hot throw is weak, the first adjustment to check is the wick size for the container diameter — before increasing the amount of fragrance.
How much fragrance should I add to soy wax? The standard sector amount sits in a range that depends on the type of wax and the fragrance, and wax suppliers usually state the maximum recommended fragrance load for their product. Exceeding it doesn't necessarily produce more hot throw — excess fragrance may not fully incorporate into the wax and can cause safety or surface-finish problems.
For more on how to choose the right wax for each type of candle and its impact on these problems, the guide to types of candle wax covers the differences between soy, paraffin and blends from the maker's angle. Candeliss materials, including soy wax and wicks in different sizes, are at candeliss.com/tienda.