Flash points are often misunderstood, even among the most experienced candle makers. In the simplest terms possible, a fragrance oil’s flash point refers to the temperature at which vapor from the oil may ignite when exposed to an open flame. That sounds scary, but it probably doesn’t mean what you think. If you’ve ever felt confused about flash points, you’re definitely not alone.
What exactly is a flash point?
Oddly enough, it really depends on who you ask. One of the reasons candle makers get confused about flash points is that some authorities on the topic don’t even understand flash points themselves and unintentionally spread misinformation because they don’t want anyone to get hurt. Erring on the side of caution is understandable, but it just ends up creating more confusion.
As we said above, a flash point is the temperature at which a fragrance oil may combust or ignite when exposed to an open flame or spark. Most fragrance oils we sell have a flash point between 141° and 200° F (or higher). If you consider that the flame of a lit candle exceeds temperatures 1000° F, you might be wondering why a fragrance oil with a flash point well below that temperature won’t burst into flame when you light your candle.
Here’s why: In order for a flammable liquid (such as a fragrance oil) to actually combust at its flashpoint, there needs to be a large volume of fragrance oil and the oil must be in an enclosed vessel when vapor emitted from the heated oil comes into contact with a flame, spark or other source of ignition. A candle with a normal fragrance load (say, 10% fragrance oil-to-wax ratio) doesn’t even come close to falling under this definition.
This doesn’t mean fragrance oils aren’t flammable, because they are. You could hypothetically find yourself at risk of igniting your fragrance oil at home, but the normal process of making candles would never put you in such a situation.
For example, if you were to heat a pot full of pure fragrance oil (no wax, just oil) to the temperature listed as the fragrance oil’s flash point and then light a match at the surface of the oil where it has begun to vaporize due to the heat, the vapor would potentially ignite and put you in danger of being burned. Fortunately, this is not a situation you would ever find yourself in while making candles safely.
Will my fragrance burn off if I heat it beyond its flash point?
Nope. A flash point is not the temperature at which your fragrance oil will “burn off” or begin to dissipate. In fact, “flash point” is actually a legal term (more on that later) and has nothing to do with the performance of your candle’s fragrance. The reason so many people get flash points wrong may come down to the fact that the word “vapor” is used in the definition of flash point. There is a common misconception that fragrance oils added to hot wax will vaporize and therefore not smell as strong.
Adding fragrance oil to wax that is hotter than the fragrance oil’s flash point won’t affect how strong your candle smells. However, there are other mistakes that may lead to weak-smelling candles. For example, heating and cooling a pot of fragranced wax over and over again can begin to affect how strong your candles smell in the end. For the best outcome, it’s recommended to heat small batches of fragranced wax and pour your candles right away.
So why do flash points matter?
One of the most important things to understand about this topic is that a flash point is a legal term used to identify which substances can be safely transported on an airplane. As we’ve learned, it actually has nothing to do with fragrance performance.
A flash point is legally defined as “the minimum temperature at which a liquid gives off vapor within a test vessel in sufficient concentration to form an ignitable mixture with air near the surface of the liquid” under 49 CFR § 173.120 of the Code of Federal Regulations.
The key word in this definition is “ignitable,” meaning that the vapor has the potential to catch fire, but in order to do so, there would also need to be a source of ignition such as a spark or flame. It’s pretty unlikely for a flammable liquid to be exposed to a source of ignition while being transported via air, but out of an abundance of caution, the law does not allow liquids with a low flash point to be delivered by air.
If you’re still wondering what all this has to do with making candles, it really comes down to ordering fragrance oils online. Under the law, flammable liquids (including fragrance oils) with a flash point at or below 141° F cannot be transported by air due to their potential to ignite under the very specific circumstances we discussed above. That’s really all you need to know about flash points as a candle maker.
What about gel candles?
We don’t currently sell supplies for making gel candles, but if you use gel wax to make candles, it’s important to be aware of additional safety precautions. Gel wax has different properties than coconut wax, soy wax, paraffin or beeswax. As such, gel wax manufacturers recommend that you only use fragrance oils with a flash point of 170° F or higher when making scented gel candles. See the manufacturer’s full safety recommendations here.
Because no one wants their scented candle to explode or burst into flame, it’s easy to understand why so many candlemakers are worried about flash points. Having a full understanding of flash points will keep you safe, but it will also help take your candle making game to the next level.