Have you ever thought about paper and how quickly it seems to burn? I mean, we just take it for granted that it burns quickly, but have you ever thought about how or why?
In this article, we are going to be exploring the physics of paper, looking in particular at the way in which paper burns, its igniting temperature, and its combustion temperature. We will also be exploring the same questions in regards to cardboard, paper’s thicker cousin if you will.
So, if you have some burning questions about paper (pun totally intended) that you cannot wait to answer, we might just have the answers you are looking for.
What is the burning temperature of paper?
It is a popular belief that paper burns at around 451 degrees Fahrenheit. At least that is what is commonly reported (and perhaps heavily influenced by Ray Bradbury and his book about burning books). However, isn’t this a little strange to you?
Surely paper burns at a much lower heat than this? I mean, it literally is the definition of paper-thin and it can be burnt with the end of a cigarette.
Something else of importance that we want to note is the fact that this is quite a varied answer, as it will also depend on the type of paper you are burning.
I mean, most of the time, fire will remain the same, no matter what has ignited the fire (be it matches, a lighter, or firewood), but the type of paper may vary.
For example, you may get different results based on the materials the paper is made from, the thickness of it, whether it is colored, and how wet or dry it is.
Because of these reasons, the figure reported of 451 degrees Fahrenheit is actually an average temperature. The actual figure can vary from between 424 degrees Fahrenheit and 475 degrees Fahrenheit. For our metic readers, this is around 218 degrees Celsius and 246 degrees celsius.
You should also consider the fact that the definition of burning may be varied, too. It could mean one of three things. For example, asking at what temperature paper burns could be referring to the temperature at which a naked flame can set a piece of paper on fire.
It may actually refer to the temperature it needs to be for the piece of paper to just burst into flames spontaneously (wow that would need to be a hot room).
Lastly, it may even refer to the temperature that is given off from the piece of paper when it is burning (i.e the what that it gives off).
Of course, this is without considering the changes that the area around the fire and flames can have on the temperature. For example, any atmospheric pressure drops can really impact the temperature at which paper burns.
That being said, this may not actually be too much of a concern unless you are within a lab where you can physically control the pressure of the atmosphere (or, y’know, at the top of Mount Everest or the bottom of the sea).
With all of this in mind, it is clear that the exact temperature that paper burns at could be varied. Needless to say, whatever that temperature is, it’s going to be hot, hot, hot!
What is the Ignition Temperature of paper?
So, remember in the previous section when we pointed out that the meaning of ‘burning’ could refer to a number of things. Well, this is one of them! The ignition temperature of something is the temperature at which a naked flame can light something on fire.
You may be thinking this is a trick question. After all, aren’t all flames hot? Surely any flame could ignite a piece of paper, whether that be a candle flame, a match, or something else entirely.
Well yes, you are mostly right. This is because most flames are hot enough to burn the paper. However, you should also consider that different parts of the flame are different in temperature.
The hottest part is the center of the flame which is often blue in color. If you put a piece of paper into this then it will almost certainly burn. Even on the slightly cooler outer part of the flame, your paper will likely burn.
However, if you hover it just above the flame, the results are less obvious. It will depend on the temperature, the distance from the flame, and the paper itself.
Now, it is worth pointing out that the temperatures of different types of flames are actually quite different. For example, for a regular candle, you can expect a naked flame to have a temperature of around 1670 degrees Fahrenheit. Super hot, right?
Well, just wait until you hear this...it jumps up to 3,488 for an alcohol flame, and a whopping 4074 for a flame from a Butane-containing lighter (like the ones that are used for cigarettes)!
So, as you can see, the igniting temperature is very varied!
What is the Combustion Temperature of paper?
So, as we mentioned at the beginning of the novel, Ray Bradbury’s novel 451 Fahrenheit has led people to believe that this is the temperature at which books can spontaneously burst into flames.
This has been widely accepted, but it has now come to light that scientists think this figure is actually a little low. In fact, it is more likely to be around 481 degrees Fahrenheit, a good 30 or so degrees higher. Sure, a minor amount, but interesting all the same.
Does that mean you can start throwing books into an oven or room heated at 481 degrees Fahrenheit and watch them spontaneously combust?
No, it doesn’t, because at least for a little while, the paper will just absorb the heat and act as an insulator. Besides, you may need more oxygen to actually set it alight.
That being said, it will eventually catch alight, and when it does it will burn very quickly, and in just a minute it will turn entirely to ash.
Therefore, as you can see, the combustion temperature of a book is 481 degrees Fahrenheit (or higher if possible). Although the conditions need to be exactly right for it.
As a side note to this point, it is worth noting that this may also depend on what the paper is made from. The majority of paper is made from wood pulp, and it is the wood pulp paper that burns at 481 degrees.
However, you should consider that, if the paper is made from another material such as Rayon or Cotton, then it may burn at a higher temperature (up to 1022 degrees Fahrenheit).
That being said, it is unlikely that your paper will be made from this, so you can just stick with 481 as your figure!
How hot is the Hottest Part of paper fire?
So, finally, we need to consider the temperature that is emitted by the flame of a paper fire. Remember when we talked about the different definitions of burning earlier? Well, this is one of them!
Now, regardless of how the paper was set alight, whether by igniting on a naked flame or combusting because of the heat around it, it will also give off a unique temperature. Fire is hot and in this section, we will establish just how hot it can be.
Of course, this is not easy to measure, and unless you are in a lab setting with all the essential safety gear, you should never attempt to figure this out at home.
However, we are pleased to report that other researchers have found that the hottest part of the fire given off by burning paper can reach around 1600 degrees Fahrenheit.
This is based on the assumption that nothing else is being done in the environment in which it is burning to increase that temperature further, of course. This is merely an estimate, but in any case, it is mighty hot!
What is the Ignition Temperature Of Cardboard?
One other consideration to make is in relation to cardboard. Cardboard is much thicker than paper, and whilst it is similar, it is likely to behave differently in relation to fire.
What we mean is that the temperature needed to ignite something as thick as the cardboard will likely be much higher than paper. The combustion temperature will also be higher.
This thought process is of course correct, and we can confirm that in general, it is thought that cardboard needs 300 degrees Fahrenheit more than paper to be set alight. This means it needs around 800 degrees, making it slightly more difficult (but still definitely likely) to set on fire.
What is the Flashpoint?
Flashpoint simply refers to the ignition temperature and combustion temperature. In cardboard, this is the same, and it is 800 degrees Fahrenheit. As you might have guessed, this is varied when it comes to paper but will be around 300 degrees lower.
So, to answer the original questions regarding the temperature at which paper ignites, combusts, and burns, the answer is not quite as straightforward as you may be wishing. As our research has found, many variables must be considered.
In terms of combustion, the exact temperature needed for a piece of paper to spontaneously set alight is varied. Certainly, it will be a little higher than novelist Ray Bradbury’s combustion claims of 451, but not by a lot. 481 degrees is the accepted amount.
In terms of ignition, the paper will likely burn on any flame since all flames will be over this 451 degrees Fahrenheit mark. That said, it may depend on the type of paper, the flame, and where on the flame the paper is placed.
The temperature given off by a paper fire is also varied, but it is thought that it can give off around 1600 degrees Fahrenheit, which is hotter than we can even imagine!
Suffice to say, any fire experiments should be left to the professionals, and regardless of what flame you are near, keep paper far away or else you could accidentally set the whole place on fire, and yourself and others, at that!