Should You Care About Flash Point?
If you’ve ever looked at a bottle of fragrance oil from a supplier there’s a good chance the flash point is listed on the side.
Not every supplier labels the flash point so directly, but some of them do.
The purpose of this article is to break down whether or not this temperature is something you need to factor into your candle making or not, but it’s better if we start with a definition first.
What Is A Flash Point?
Many fluids give off vapors, which is the point in time when the liquid starts turning into a gas.
If you’ve ever boiled water, you’ve seen this behavior: vapor comes off the surface of the water and evaporates.
Vapors play a role in fragrance oil too!
Generally speaking, the warmer a fluid is the more it wants to “release” vapors to the atmosphere, but cooler liquids hold their vapors much better.
The flash point is the temperature where a fluid (any fluid) gives off enough vapor that an open flame could ignite it quickly. Not a full on continuous fire, but a brief flash of light.
The only thing that can ignite the vapor is a true ignition source, not just heat.
For example, submerging a fluid that is heated to it’s flash point temperature in a super hot wax (as is the case with adding fragrance oil to wax) won’t ignite the oil, but lighting a match (an open flame) over it will.
How does this impact candle making?
Two Schools of Thought
The first group believes flash points impact your scent throw:
“Adding fragrance oil to wax heated above the fragrance oil’s flash point will degrade the fragrance, damaging the lighter notes and resulting in a weaker hot throw.”
The second group believes the opposite:
“You can add fragrance oil to wax at any temperature, regardless of the flash point and it won’t degrade your fragrance oil or negatively impact your scent throw.”
We’ll start by figuring out what causes fragrance oil to degrade.
How Does Fragrance Degrade?
Two primary culprits: light and heat.
Light, or more specifically, the rays of energy hidden from our eyes, can damage bonds in fragrance.
Store them in darker areas to prevent this, but the total damage from light on fragrance is typically far less than what heat causes.
Sure, if you left a bottle of FO outside in an Arizona summer it would make an impact.
Leaving it in your workshop underneath lights? Likely not going to disrupt your operation in any way.
Heat is another story.
Perfumers are quick to warn against the dangers of subjecting fragrance to heat, but when does temperature become a problem with oils?
Fragrance oil loses scent through evaporation of notes.
Although each oil is a collection of complicated compounds, every note in a fragrance has some level of volatility.
Remember the fragrance pyramid?
Top notes evaporate much faster than base notes because they’re more volatile. Once they evaporate, they’re gone.
Heat accelerates the evaporation process, meaning if you raise the temperature of fragrance oil it will evaporate faster than if you left it at room temperature.
The critical temperature associated with volatility is called the boiling point.
When fluids reach their boiling point, they evaporate. In a fragrance, the individual components (top, middle, and base notes) have different boiling points.
Higher volatility means lower boiling point. Lower volatility means higher boiling point.
In a highly simplified explanation, fragrance won’t lose scent (degrade) until any of the notes reach their boiling point.
Again, this is simplified tremendously, but the spirit of explaining it this way helps set the stage for how flash point impacts degradation.
Does the Flash Point Temperature Degrade Fragrance Oil?
Fragrance only degrades if notes evaporate or burn off because the compounds reach their boiling points.
Once fragrance reaches the flash point, it’s capable of having the surface quickly ignite, but isn’t outright evaporating itself into the atmosphere.
Ignition has to come from an open flame, not just something hot, and the fire won’t remain for more than a few seconds (if it even lasts that long).
If the surface of a fragrance ignites, some of the scent will literally burn off since it provides fuel for a short-lived flame.
Simply warming a fragrance oil to the flash point doesn’t create mass-evaporation of the notes.
If the fragrance is raised to the boiling point, then mass-evaporation would occur and a lot of scent would leave the fluid.
But this use case only applies to the fragrance oil by itself.
In candle making, fragrance oil is added to hot wax which creates a mixture. This means the effective properties of the blend aren’t those of wax OR of fragrance oil – the properties are a mixture of both.
| Item | Flash Point | Boiling Point |
| Fragrance Oil | 115°F – 200°F+ (46°C – 93°C+) |
>200°F (>93°C) |
| Wax | 392°F – 464°F (200°C – 240°C) |
650°F – 720°F (343°C – 382°C) |
| Fragrance Oil + Wax | 365°F – 438°F (185°C – 226°C) |
605°F – 668°F (318°C – 353°C) |
And since wax typically takes up about 90% of blends, the properties will sway closer to the wax than fragrance oil.
Now, these are rough estimates. To really find out what happens under the hood you need two things that are hard to come by:
- Full chemical makeup of the fragrance oil and wax
- Deep understanding of organic chemistry
Which means there’s definitely going to be question marks since obtaining the second point is actually easier than the first!
The point remains: you can safely add fragrance oil to hot wax, even if the temperature of the wax is higher than the fragrance oil’s flash point. Why?
- Flash point only matters when ignition occurs
- Degradation happens when evaporation starts, which occurs at the boiling point (much higher than the FP temperature)
- The relevant properties for making candles are the mixture properties
Conclusion
Flash point isn’t relevant for making candles and should be ignored entirely when considering what temperature to add fragrance to wax.
The primary reason suppliers include it on their bottles is related to shipping (read more about that here).
In short, airlines won’t move substances with certain chemical properties for safety reasons.
Unless part of your process involves lighting a match over the surface of the fragrance, you won’t lose any scent from those temperatures.
Some advice percolates the internet suggesting you should add your fragrance far below 185°F (85°C) to avoid scent loss (keeping it below the FP).
Doing this can be a safety hazard because stirring effectively to blend the FO and wax is harder at lower temperatures.
Make sure to stir for at least two minutes, regardless of when you add fragrance, to avoid poorly blended candles.
When fragrance isn’t mixed, it “pools” inside the candle, leaving pockets of FO with potential to catch fire during use.
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