How Do Candles Work?

Good question!

A lot of this is common sense and may seem straight forward but anyone who has tried their hand at candle making will attest that it’s not always as straight forward as it seems! Grasping the minute mechanisms of how a candle functions will only help with successful candle making.

A scented container candle comprises of wax, wick, container and fragrance - in its simplest form.

Candles work in a fairly inter-dependent manner once the initial ignition of the wick occurs. If left undisturbed, a candle will in most cases burn continuously until there is no wax left and the wick is consumed.

In order to function a candle requires a source of heat (flame from a match, say). This flame is used to ignite the wick to get the party started. Most wicks are supplied with a coating of paraffin wax, which is perfect for combustion. The ignited wick provides the means to melt the wax. The wax is a source of fuel for the flame. The burning wick melts the wax, vaporising it. As the vaporised fuel combines with oxygen in the air it provides a constant flame. The flame needs to provide enough heat in order to melt the wax (fuel) keeping the candle burning in this manner. If a wick is doing its job correctly then it will melt the wax on the surface turning the solid fuel into a liquid where the wick, using capillary action (drawing-in) draws the fuel upwards towards the flame where it vaporises - fuelling the candles flame. Capillary action is often called wicking - hence why wicks are called wicks! This series of events should continue until there is no fuel (wax) left or the wick is fully consumed (extinguishing the flame) or something else happens to disturb the cycle (a gust of wind for instance). 

With continued use, a candle will use up its fuel source and the candle itself will become shorter as the wax fuel is consumed.

Wax is a pretty useful material beyond its use as a fuel - it doesn’t mind carrying stuff like fragrance oil and dye.

Wicks

As you might have read in our previous post, in the 18th century a self-trimming wick was developed which helped to regulate flame size. Braided wicks curl when burning with any excess piece of wick (not emitting vaporised fuel) consuming oxygen and being incinerated by the flame. These wicks will still require trimming manually between uses (ca. 5mm does the trick!). This is an important development as wicks which are self-regulating not only keep the wick itself neater, but it also regulates flame size maintaining a more consistent burning temperature and as such, a regulated rate of fuel consumption. If the rate of fuel consumption is regulated, the burn rate of the candle is consistent meaning a slower, steadier burning candle (in theory), but only if the wax and wicks are suitably matched.

Excessively smoking candles are usually the result of flame disruption, by a draft or too long a long wick. By keeping wicks nice and trimmed and out of draft-prone areas, your candle should not smoke as much. But of course, like anything that burns, smoke is a given! Smoke and soot are produced in every candle as the burning of organic compounds produces carbon due to incomplete combustion. A candle will produce more soot if the wick length is not correct and/or the flame is disturbed, say by a draft, wick mushroom* or any foreign debris in the wax. 

We advise that a candle should be allowed to burn for around 2 hours after the initial burn, itself usually requiring between 3-4 hours. Ideally a candle shouldn’t be left to burn for longer than 4 hours as, if left to burn for too long, its burn behaviour eventually deteriorates as the rate of evaporation, capillary action and the increasing volume of molten wax overwhelms and disrupts the process. Not to mention the container can become excessively hot which isn’t too safe.

Much the same as waxes, there are many different wicks one can use. We use an unbleached and sustainably sourced cotton and linen fibre for all of our candles. The wicks we use have a single coating of Paraffin wax to help with combustion and to reinforce the structure of the wick.

Other wicks may comprise other natural fibres, different paper stocks and some also have metal cores or structures. We opted for ones without metal cores or structuring. Our wicks have a small steel tab on the end, which secures to the container – this not only helps fix the wick in place but also ensures the wick braids are held together. The wicks we use are lead free.

There are other wick types available such as wooden wicks, but we dislike these both aesthetically, functionally and ecologically.

*Pause – wick mushrooms?

Mushrooming is a term for an abundance of matter on the end of the wick. This doesn’t happen to all wicks as it is dependent on several factors. If you witness this, you will see that the end of the wick where the abundance collects sits in the centre of the flame and rarely protruding out the flame – this is important to observe as will be discussed.

In short, no candle is 100% efficient and as such candles left to burn for extended periods of time may not consume the fuel (molten wax) at a steady pace. External conditions such as room temperature and air circulation may also affect the physical burning performance of a candle and of course this is a variable that will be different each time you use your candle. Candle mushrooming may not occur at all throughout the entire life of your candle or they may occur irregularly depending on the conditions.

All of these factors can produce a build-up of carbon and can amass on the end of the wick - where oxygen is usually drawn to regulate wick length. The abundance can interfere with the self-trimming mechanism so more wick material stays put, gathering up in the centre of the flame where it would usually protrude, drawing oxygen and eventually incinerating. As mentioned, to function properly the part of the wick that is no longer consuming fuel requires jutting out of the flame where it consumes more oxygen and eventually is incinerated by the flame itself. As the candle mechanism is inter-dependant and surprisingly fragile (each part needs to play its role well), any interference with the flame will produce additional smoke and flickering - candle ‘mushrooms’ will therefore exacerbate this behaviour.

Additionally, a wick that is too large for the container and wax composition (fragrance concentration should also be taken into consideration) may also display inefficient burning performance leading to the above.

Candle making is really an art of balance - too small a wick (or the wrong wick for the wax type and fragrance) and the candle doesn’t burn well; too large a wick and it also doesn’t burn well. Of course, there are wick sizes that are more suited to the variables in question and perform better than others but generally speaking it really is more ‘best-fit’ rather than an exact science. Pretty annoying really!

Pairing candle containers, wax types, wicks and fragrance oils is all part of the development process. At HEROWN we match the wax, wick, fragrance and container size so as to optimise the burn performance as best as possible. Hopefully any mushrooms that do sprout from your HEROWN candle wick are small enough to deal with, we have tried our best to match all variables so as to produce the highest quality, most efficient and sustainable candle product

What about scent?

A scented candle comprises the functional components: container, wax, wick and then the accessory products. The only accessory product in HEROWN candles is fragrance, although some candles out there feature other accessory products such as ‘crystals’ or other added objects.

To keep it brief, fragrances vaporise into the air. The mechanisms required for effective candle performance are excellent ways to enable this vaporisation.

For HEROWN candles, the fragrance itself is formulated specifically for use in candles.

Fragrances used for candles need to function differently to fragrances used on the skin. The fragrance itself may consist of numerous materials: tens or over one hundred. The individual aromatic raw materials comprising the fragrance are sourced from natural and/or manufactured origins. At HEROWN we use a balance of both for an ecologically sounder product and, in our opinion, better end results! Nature gives us some gorgeous raw materials but clever people in big efficient fragrance companies also create beautiful raw materials. Some aromatic materials work better in candle applications than others but there is no advantage to using only natural or manufactured materials and neither source of aromatic materials are safer than the other.

Not all aromatic raw materials like being subjected to heat or being carried by wax and as such not all aromatic materials are used in candle formulations. That goes for both natural origin and manufactured materials. Some fragrance materials are dense and viscous and as such present complications for the mechanism – wicks can become clogged if an aromatic material is too thick or sticky for example. 

Anything else worth noting?

Yes, let us just drop in our two cents on too often overlooked aspects of candle making which do have an impact on the final product…

Containers:

There are two main types of candle – pillar and container. Pillar candles are generally firmer and allow for the candle to burn freely down the centre, creating a wall of wax (basically a wax container for the molten wax).

Container candles hold the wax in a vessel. Some may be found in tin or other container types, but we opted for good old glass. But it’s not just a question of any old glass; the way in which heat circulates and acts on the glass walls is important. The glass must be able to withstand the temperature fluctuations a candle subjects it to – hot, cold, hot, cold etc. The glass must have tolerance and quality glass candle containers are manufactured to withstand all of these fluctuations.

The containers we use at HEROWN are heavyweight, thick-walled (which concentrates the heat on the inner side of the glass helping to melt the wax) and are wide-mouthed, which helps with diffusion of aroma, but does mean there may be some residual wax after each optimal burning session. This isn’t a worry, as any residual wax will eventually melt with use.

With that said, a candle container will become hot when lit and caution must be taken if touching the candle whilst lit or immediately after burning. Consider the surface you are burning your candle on too. Hot glass can mark and damage some surfaces.

Temperature:

Arguably, the most important factor for making any candle is - drum roll please - temperature! The best wax, wick, fragrance, additive and the fanciest of container means nothing if you don’t get your temperatures right during the making of the candle. If the temperatures aren’t right, it will have an adverse effect on the overall performance of your candle.

There are a surprising number of important temperatures to consider when making candles – it is not just a case of melting wax, throwing the components together all at once and expecting a good result. Room temperature, wax melting temperature, subdividing temperature, fragrance inclusion temperature, container temperature, pouring temperature, ambient temperature whilst solidifying, re-pouring temperature, storage and shipping temperatures. This can be a tricky obstacle as it is pretty difficult to control temperature accurately and consistently.

In our opinion, temperature control is the most frustrating element to making any candle. They don’t really tell you that before you start though!