The Science & In-World Reason for Azula’s Blue Flames
It’s not temperature that yields blue flames, but oxygen, cleanliness of the fuel, and complete combustion.
In this essay, I explain why fire has its typical colors (red, orange, yellow) and why blue is, in actuality, the true color of fire (it really is and you will see why). Afterward, I propose an “in-world” theory for why a firebender’s flames can be blue.
This is a technical heavy article, but if you stick with it, you will have both a detailed understanding of what gives fire its color and a theory for why Avatar’s most iconic villain can generate blue flames.
Introduction
I’m sure you’ve wondered the following: why are Azula’s flames blue? It’s true that Bryke stated they gave Azula blue flames for cinematic reasons (to differentiate her from Zuko in the hypothetical final battle), but this answer is not sufficient for Avatar’s worldbuilding. Since the franchise has not provided an explanation for blue flames in the eighteen years since Azula’s prodigious firebending first appeared, we must develop our own reason that builds upon, and builds out, Avatar’s lore.
I’m also sure you’ve heard the following: Azula’s flames are blue because they are hotter. Makes sense, right? Blue stars are blue (versus red or white) because they are much, much hotter compared to our “cooler” yellow sun. Just look at the following picture. It demonstrates that as stars get hotter, their visible light shifts toward blue and indigo.
The star in the middle is a “white” star since it contains equal parts all other colors. Our Sun is actually a white star. The reason it appears red, orange, and yellow is because the atmosphere filters out the cyan-through-indigo spectrum of light. It is worth noting the temperature difference between a white and a blue star: a white star is 10,000 degrees Fahrenheit on its surface while a blue star is over 30,000 degrees. Does this mean Azula is shooting blue star, nuclear fireballs out of her hands???
No.
Think about the Sun again. It is a white star. Its surface temperature is around 10,000 degrees Fahrenheit. Now think about the picture at the head of this article: a gas stovetop burning with blue flames. Blue, like a blue star. The temperature of that stovetop’s blue flames is around 3600 degrees Fahrenheit, yet the surface of our not-blue Sun is 10,000 degrees.
Why?
Because blue fire is not blue due to its temperature.
It’s blue because that’s the actual color of fire.
The Colors of Fire
When referring to “fire” in the case of Avatar, we're referring to the glowing plasma that results from the combustion of carbonaceous, hydrogenated materials (e.g. wood) with air (oxygen).
Yes, Avatar is a fantasy world with an unexplained, magical elemental control system, but when Uncle Iroh talks about a firebender’s energy coming from “the breath”, this implies air, which implies oxygen and, therefore, normal air-breathing fire rather than burning metals, like fireworks, which is a different phenomenon.
When wood, coal, alcohol, lighter fluid, etc. burn, they release a variety of chemical products, called “species”, such as Carbon-Carbon and Carbon-Hydrogen, that get “excited” by the chemical reactions of the combustion process. This “excitation” means the electrons surrounding those chemicals have too much energy, which they want to release. These electrons release this energy by forcing their host species to combine with Oxygen to form Carbon Dioxide and Water, thereby completing the combustion process. When these excited electrons release their energy, they do so in the form of heat and visible light. This visible light lies mostly in the “blue” spectrum.
The picture below depicts the visible light given off by these chemical species during the combustion of butane, which is used in lighter fluid. The Carbon-Hydrogen specie is responsible for the deep blue color, whereas Carbon-Carbon provides the more translucent cyan shades.
The next picture depicts the entire visible light spectrum, with the same 425-to-525 nanometer wavelength range highlighted.
BUT FIRE IS RED, ORANGE AND YELLOW.
It can be those colors, and almost always is, and here is why:
Fire takes on reds, orange, and yellows due to soot, debris, and other incompletely-combusted particles heating up in the otherwise blue flames and emitting those wavelengths of light due to the phenomenon of “incandescence”. When a flame is any color other than blue, it is the glowing, incandescent materials that dominate. This is why the bottom portions of candlewicks tend to be blue, because the combustion down there is clean and soot free.
Remember that incandescence is an object glowing red, then orange, then yellow, then white with increasing temperature. It does not result in blue until an object approaches obscene temperatures, such as those found in the hottest and brightest of stars.
Blue flames result when a fire has enough or excess oxygen, and the fuel it is burning is free of impurities. Those chemical species I mentioned earlier burn completely when there is excess oxygen available, resulting in water, carbon dioxide, heat, and blue light. When there is plenty of oxygen, those blue-glowing chemical species dominate a flame’s color because there is no soot, debris, or incomplete combustion to cause red, orange, and yellow colors. Even though blue flames are hot enough for incandescence, the blue light released by those species dominates.
The picture below depicts a Bunsen Burner showing different flame conditions. The flame on the far left (1) is burned with excess fuel whereas the flame on the far right is burned with excess oxygen. Note the differences in color. The excess fuel on the left is not burned, creating ash, soot, and incomplete combustion products. These substances are heated up and glow red-orange-yellow, whereas, in the oxygen-rich flame, all fuel is combusted, resulting in blue fire.
However, a blue flame can be turned red, orange, and yellow if enough “dirt” enters its fuel to create soot and incomplete combustion products. Wood, for instance, holds many of these substances.
This is why gas stovetops burn blue while a chunk of wood is full of reds, oranges, and yellows. The methane (natural gas) and propane of your gas stove are nearly all carbon-hydrogen molecules in gaseous form, and contain no dirt, metals, sulfur, nitrogen, or other contaminates that would change the color of their flames. Additionally, since wood and coal are solid, it is much easier for microscopic bits of unburned fuel to be thrown up into the flames and add to the volume of incandescent debris.
Another example is setting alcohol on fire. Yes, you can get whiskey or sake to burn, but it must be heated to just below boiling (don’t try this at home). Alcohol burns a pale blue because it is free of noncombustible debris.
A blue flame indicates highly efficient, oxygen-rich combustion, not temperature. You can have a “cold” blue flame just as easily as a “hot” yellow flame, or a hot blue flame and a cold yellow flame. It depends on the amount of soot and debris.
For an Avatar-related note on incandescence, in Season 2 of Avatar, Azula’s blue flames were drawn with a lot of “brightness” to them. This would be an example of incandescence, where the temperature is high enough to overpower the blue glow of combustion. Oxyacetylene torches can burn at over 6000 degrees Fahrenheit, resulting in shining, blue-tinted light, but only at the very tip where these ultra-hot flames are concentrated. The blue flames that result from burning oxygen with acetylene, which are among the hottest flames attainable, generally look like this:
Look familiar?
To summarize, a normal air-breathing fire actually gives off blue light, but soot and contaminates transform its blue colors into the familiar reds, oranges, and yellows we typically associate with fire (as does the Fire Nation with its numerous shades of red), whereas fire burned efficiently, with no soot or contaminates in its fuel, produces blue flames, or the natural color of fire.
Fire burned efficiently. Free of contaminates. The natural color of fire. Sounds familiar...
Sounds like her.
The In-World Reason for Azula’s Blue Flames
To this day, the Avatar franchise has not provided a reason for Azula’s blue flames. Since the Avatar world was created with an impressive level of detail that allows a myriad of ways to relate the show to the real-world (see: The East Asian Origins of the Fire Nation and its Villains), then it stands to reason that Azula’s blue flames should be just as nuanced and meaningful.
At the same time, Azula’s ability to conjure blue flames should also tell us something about firebending in general. For instance, Uncle Iroh’s lesson on lightning taught us how firebenders direct chi through their bodies, and in the Avatar and the Fire Lord, we saw Sozin draw the energy out of magma, and thereby cool it, as if he was redirecting lightning through his body.
We have not seen anything similar for Azula’s blue flames.
Finally, since Azula’s blue flames are a unique character trait, her ability to produce them should tell us something about her. Note that Toph’s metalbending taught us about both Toph’s character and the philosophy of earthbending. This is what blue firebending should do for both Azula and firebending itself.
Unfortunately, Avatar’s bending was not created by Brandon Sanderson, so we barely have an understanding of how it works on a technical level.
However, we do know that firebenders direct chi through their bodies, according to Uncle Iroh. Instead of merely controlling an external element, they actually produce something with their chi. Presumably, they are using their chi to produce heat and that heat is expressed as flames.
We also know that firebenders require a “drive” to produce their flames, but why this drive is needed, or what it does, we do not know. All we know is that firebenders control the flow of energy in their bodies and in objects around them, that their chi can take the form of fire and lightning, and that they need a “drive” to make their firebending work. Despite these uncertainties, chi appears to be at the center of firebending in a way that it is not for the other bending forms.
Fortunately, we have a character in Avatar, and an entire episode, dedicated to teaching us about chi and how it flows through the body.
According to Guru Pathik, the chakras can obstruct the flow of chi through a person’s body.
Guru Pathik describes the chakras as “pools of spiraling energy” that flow into one another via small creeks, but because life is messy, things can fall into these pools and clog the creeks connecting them. These clogs can either reduce the flow or stop it altogether.
Guru Pathik’s explanation of chakras might explain why firebenders need a “drive” to produce their flames. Since most peoples’ chakras are probably clogged to some degree, this “drive” is needed to “force” their chi through the clogs. The clogs don’t go away, but their drive “squeezes” the chi through the gaps, allowing it to flow through their bodies. If a firebender loses their “drive” and doesn’t have the ability to spiritually open their chakras, their chi won’t flow and their firebending won’t work, like what happened with Zuko.
Guru Pathik did not say that opening and closing the chakras is a one-time event. Presumably, if one knows how to identify their closed chakras and how to open them, they could do so at will, as is the case with the Avatar State. Along these lines, a firebender could also learn to open their chakras at will.
Uncle Iroh said that lightning requires “peace of mind”, that it is firebending fueled without emotion or aggression. This could imply it requires your chakras to be open rather than a personality trait in the bender. Iroh certainly doesn’t act precise and deadly.
Since blue fire is the natural color of fire, burned without impurities, where all the energy (fuel) goes into producing heat and flames, this implies that a firebender producing red, orange, and yellow colors has impurities in their flames. Since a firebender’s flames are an expression of their chi, this means their chi is what is impure, not the flames themselves.
Guru Pathik said that if the chakras are open, the chi flows freely and the pools stay clear. If the chakras are clogged, the pools become dirty. If a firebender uses their drive to force their chi through the dirty pools, their chi becomes dirty as well. When this dirty chi turns into flames, it shows the reds, oranges, and yellows of sooty, dirty, “impure” fire.
On the other hand, if a firebender’s chakras are clean, their chi is clean, like butane or alcohol, and the flames are expressed as blue.
Guru Pathik did not say that opening and closing the chakras was a matter of being devoid of any problems in one’s life, but knowing how to open them. It’s a skill that is learned.
A skill.
Aang had to learn the skill of opening his chakras. Other firebenders could also learn that skill.
Azula is referred to as a prodigy. She is also shown to work hard in developing her innate talents. All inherently talented athletes who become “great” work hard to hone their innate abilities.
Bending in Avatar is portrayed as being both a skill and a talent, it has to be taught and practiced. Azula practices, a lot, and she is hard on herself about it. She is taught by presumably the best teachers in the world and she has the innate talent to improve her skills.
The reason for Azula’s blue firebending is this: she has learned the skill of opening her chakras when firebending. Her flames are blue because her chi is clean when she firebender, it has not been driven through clogged chakras, yielding the color of pure fire.
What clogs her chakras that requires her to open them? We don’t know. Lots of things can, according to Guru Pathik, and Azula certainly isn’t without problems.
How does she open them? Presumably she learned how to “let go” of certain things like Aang had to. We know what allowed Aang to let go was his pressing need to be the Avatar. Perhaps what allows Azula to “let go” is her pressing need to be a competent, fearsome princess.
Why can Azula do this but nobody else seemingly, such as Iroh? Who knows, but then again, why is Katara so inherently good? Why Toph is both blind and amazing rather than blind and mediocre?
This could be where the prodigy element comes into play. Also keep in mind that Azula is in the opening credits as an example of a firebender, alongside Pakku, Roku’s earthbending master, and an unnamed air nomad, all of whom are adults. This must mean there was something about Azula as a firebender, in the minds of the creators, that placed her on the level of middle-aged bending masters.
What about the other colors, the ones we saw the dragons produce in The Firebending Masters? Those could relate to the way chi interacts with the chakras too. In the case of blue fire, it is a firebender’s chi being free of impurities, the true color of fire. Perhaps the other colors, such as purple and green, are the result of only certain chakras being clogged while others are open.
A potential flaw of this theory is that avatars have not been shown bending blue flames while in the Avatar State, despite their chakras apparently being open. This is one example of the type of technical details we are missing about bending, as well as the functioning of the chakras themselves. Perhaps avatars’ flames should be blue while in the Avatar State, but the creators didn’t think this detail through. However, there might be an explanation for this.
Perhaps when the chakras are open, the messiness of life can still “fall in” and dirty the water, but not clog them. In this situation, the influx of dirt is faster than the inflow-outflow of clean water, turning the water murky. This could make sense: it doesn’t take much soot and unburned fuel to turn a blue flame red-orange-yellow. Turn your gas stove on or off improperly and you’ll see orange-yellow flames briefly.
Avatars have been shown angry, conflicted, and emotional while in the Avatar State, similar to how Azula was angry, conflicted, and emotional during the finale, yet she could still bend blue flames. Perhaps the secret to maintaining blue flames is both keeping the chakras open and keeping the pools of chi clear while they are open, sort of like if you pour a bucket of mud into a small creek, the creek will turn muddy until the flow has cleared the mud away. The creek is not clogged, the water has just turned muddy temporarily. Perhaps these avatars have not figured out how to keep their chi “clean” whereas Azula has.
Summary
I hope this article has informed you on the science of fire’s colors and why blue is, in fact, fire’s true color. I also hope it’s given you a satisfying in-world reason for why Azula’s flames are blue instead of being a cinematic ploy to differentiate her from Zuko.
By explaining Azula’s blue flames this way, you utilize the established lore of Avatar, expand our knowledge of the character who can produce them, and make firebending just a bit more relevant to the real world by teaching a lesson about the colors of fire.
... Or would you rather it remains a cinematic ploy?
It’s not temperature that creates blue flames, but oxygen, cleanliness of the fuel, and complete combustion.
In this essay, I explain why fire has its typical colors (red, orange, yellow) and why blue is, in actuality, the true color of fire (it really is and you will see why). Afterward, I propose an “in-world” theory for why a firebender’s flames can be blue.
This is a technical heavy article, but if you stick with it, you will have both a detailed understanding of what gives fire its color and a theory for why Avatar’s most iconic villain can generate blue flames.














