A Better Hot Throw
Hot Throw Theory
Cold throw sells candles, hot throw creates return customers.
Obviously, the “scented” part of scented candles plays a crucial role in successfully running a candle operation.
Or maybe you’re just making candles for friends and family.
Either way, every candle maker should understand how scent throw works in candles and how to increase it. That’s what this article is for.
Candles have two smells types:
Cold throw. The candle smell before burning. This is what you’d pick up and smell in a store, for example.
Hot throw. The aroma in the air while a candle burns. Good hot throw means the candle has a powerful smell.
Many people in the community debate how scent throw works.
Some believe in the power of the melt pool, others swear by the strength of the wick.
As with most arguments, the truth ends up being somewhere near the middle.
Then there’s the vast selection of fragrance oils, essential oils, wax types, and candle designs that seemingly exist only to complicate the matter.
The age old question, “why doesn’t my candle have any scent?” isn’t easy to answer. It usually prompts more investigation.
Questions that need answers before the diagnosis is ready.
While this guide aims to clear things up, it may also make matters worse.
Beginner candle makers beware! Ignorance is bliss, but knowledge is power.
This article covers the leading ideas behind scent throw in candles. How it works, what makes it tick, and how each part of the candle making and fragrance industry plays a minor role in the production of your scented symphony.
High performing candles operate in a completely balanced system.
Remember that every candle is a small combustion machine responsible for balancing fuel, fire, and oxygen.
But what about scent?
You Don't Need A Wick
Discussing scent throw is interesting because a wick isn’t necessary to smell a candle.
Wax melts and tarts are insanely popular right now and they typically perform as well as a candle for filling rooms with fragrance.
An electric heat source, typically a bulb of some kind, heats a ceramic plate with wax cubes on it until it completely melts.
Warmers rely on a critical factor of creating strong heat throw: the melt pool.
Melt pools are a liquid blend of fragrance oil and wax.
The blend travels through the wick in a candle as fuel for the flame. Warmers create a pool until it evaporates into the air.
At first glance, it may seem the wick part of a candle isn’t serving much of a purpose.
After all, why intentionally burn through the melt pool if it’s responsible for generating hot throw?
Candles Are A System
Because candles and melts are a system.
Melt pools work in tandem with temperature and air currents to lift fragrance in the air.
They are almost useless without these characteristics.
Melt pools generate the greatest hot throw when they’re at the right temperature. Larger melt pools release more than smaller.
The flame on a wick regulates the melt pool temperature in a traditional candle whereas the electric heat source in a warmer handles raising temperature for wax melts.
Finding the sweet spot for a melt pool means the aromatic compounds will lift into the air.
They aren’t going anywhere without proper air currents, but they’re ready to ship.
Unless the heat is too high.
Fragrance is fickle. Lighter, more volatile compounds in fragrance can vaporize more easily.
If the flame is too hot, a majority of those notes can burn off before they ever have a chance to compliment the air.
Conversely, when temperature is too low, the melt pool isn’t hot enough to release compounds at all.
Wicking
This is the frustrating part of sizing wicks – they not only have to balance the combustion process safely, they also need to regulate the temperature of the melt pool to release fragrance without trapping it or burning it off.
Wicks also manage the “throw” part of “hot throw”.
The flame at the top of the wick draws fuel up from the melt pool to give off carbon dioxide, water, and heat.
Heat stirs the air currents in the vicinity to literally move air and vapor around where it sits, including melt pool fragrance attempting lift off.
If the candle is located in an area with good air circulation, any compounds it manages to throw into those airways can travel throughout a room or more with the natural airflow of a building.
Sometimes great candles won’t smell from afar if they’re placed in a very stagnant location, no matter how well thrown the fragrance is.
The strength of a wick depends on the wax blend holding the fragrance.
Heavier wax, like soy, requires more oomph to throw well. Lighter waxes throw with ease, like paraffin.
Wick design matters too, which is why there are so many varieties on the market.
Most commercially available wicks are primed with another wax to enable more efficient fuel transfer.
Some wicks perform better than others in certain waxes, but almost always have a temperature rating.
Manufacturers like Atkins and Pierce list “ROC” (Rate of Consumption) on their wicking charts. Higher ROC typically means the wick burns hotter, which is necessary in higher melt point wax blends because it require more thermal energy to create a melt pool.
More Fragrance Isn't The Answer
Beginners often believe you can add more fragrance oil to craft a greater hot throw.
It seems believable, given that fragrance oil is the source of smell, but remember that fragrance oil doesn’t deliver aroma – the candle does.
Candles are a complete system where almost every factor impacts at least one other.
Fragrance oil significantly changes the burning characteristics in candles. Candles that were safe to burn before adding fragrance oil might require an entirely different wick after adding fragrance.
It could be a larger size to accommodate the new blend properties, or it may even require a different wick series.
Additional fragrance can alter the burn temperature of the flame.
In some cases, more oil actually increases the temperature of the candle so much the main compounds of a fragrance burn away leaving the stench of jet fuel in its wake.
Yuck.
So it’s critical to distinguish that fragrance oil is the “fuel”, but the candle is the “delivery system” for fragrance.
In this case, adding more fuel impacts the delivery system. This is why iterative testing is imperative to successful candle making.
Optimal hot throw comes from a proper balance of fragrance load, melt pool temperature, container design, flame temperature, and air currents in the room.
Some strong candles have a fairly minimal fragrance load.
The key is a well-designed delivery system to efficiently throw every molecule of fragrance in the candle.
Warmers don’t have wicks. Instead, they heavily rely on the ambient room to carry fragrance around. The warmers can stir the immediate air temperature up a bit, but aren’t primarily responsible for this like a candle flame is.
Wax melts can also get away with higher fragrance loads too since they are at less risk of burn-off than a candle.
Unfortunately, many wax warmers have binary temperature settings – on or off.
Variable temperature settings allow more discrete adjustments to the melt pool temperature for optimizing throw, and hot bulbs can deteriorate fragrance molecules before they can throw, especially if the melt pool is subject to high heat for too long of periods.
Curing Is Important Too
Hot throw is output by a complicated system of wicking, wax, fragrance, and temperatures.
Curing your candles plays a role too because it impacts the fragrance delivery system.
A lot of candle makers judge the success of their candle on hot throw alone, but ignore safety standards in sizing their wicks.
Curing allows the candle to “cool” beyond where the naked eye can see. Some wax takes two weeks to substantially harden.
The hardness of the wax affects how quickly a melt pool can form.
Soy candles in their first 24 – 48 hours are softer and melt easier.
This impacts the delicate balance: flame temperature, melt pool temperature, fuel rate, and fragrance dispersion in the candle blend.
Why does this matter?
The hot throw you receive before a candle completely cures is no indication your system will stay balanced after the fact.
If you’re jumping into burning too quickly and you don’t smell anything, this doesn’t mean the candle won’t work.
It means you aren’t testing the final version of that candle once curing completes.
Conversely, if you smell everything you want make sure you also test beyond the curing period to make sure the system doesn’t change too much to impact your results.
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