Is Soap Flammable? Will it Burn? It Depends…


It’s probably fair to say that nobody takes a shower while wondering if the soap is going to burst into flame and, fortunately, there would be plenty of water around to extinguish the blaze if it did. But many still wonder if soap catches fire easily or at all?

Soap is not flammable. It will melt if it gets hot enough, but it will not easily catch fire, as the flashpoint of most soap is around 1000 degrees Fahrenheit (537 degrees Celsius).

Lets take a look at what soap is actually made of and in what circumstances it can catch fire. Keep reading.

Also read: Is Hydrogen Peroxide Flammable? Examined

Can Soap Catch Fire? (Flashpoint)

is soap flammable

Yes, soap can, in theory, catch fire. However, under most circumstances, it will not catch fire when heated. 

Instead, it will melt. 

This is because it consists mainly of long hydrocarbon chains. 

This means that there are a lot of carbon-to-carbon bonds throughout the chain and it requires a lot of energy to break these bonds before the carbon can bond. 

The carbon to hydrogen bonds require even more energy to break, which is a good thing as if they broke easily – hydrogen itself is very flammable.

So, soap tends to melt which is a reflection of the bonds weakening in the hydrocarbon chains instead of catching fire.

Soap will catch fire if it gets hot enough and the individual chemicals within the soap reach their “flash point”. 

Typically, the flashpoint for most soap is going to be in the 500-600 degrees Celsius range, which’s roughly 900 – 1100 degrees Fahrenheit. 

That’s so hot that if you find yourself witnessing soap catching fire, you have much bigger problems than burned soap. 

Is Liquid Soap Flammable?

There are many different liquid soaps out there and it would be impossible to be categoric about every single one and its flammability. 

However, as you can see from this material safety data sheet – liquid soap can be flammable. This particular liquid soap will catch fire (flashpoint) between 115 and 135 degrees Fahrenheit (46 – 57 Celsius).

That makes it much more flammable than ordinary soap.

Though somewhat reassuringly it’s worth noting that this product won’t sustain a flame. 

It will catch fire at this temperature, but the fire should auto-extinguish without any input from you – so don’t rush to keep a fire extinguisher next to the liquid soap.

Is Liquid Hand Soap Flammable?

Liquid hand soap can be flammable but is not always. It will depend on the type and brand. 

In fact, this safety sheet for a particular brand of liquid hand soap says it’s not even combustible under ordinary circumstances. 

What Happens If You Burn Soap?

When soap burns it will cause black, sooty smoke as it breaks down. This is because soap is a hydrocarbon compound and when it burns it will give off carbon monoxide (CO) or carbon dioxide (CO2) and water (H2O) as its main byproducts.

If the soap is only partially consumed, you would expect it to be discolored and possibly to smell bad. 

However, if the soap does not burn but simply melts and reforms, it will probably not be much different from how it started. 

Can You Burn Soap Like A Candle?

can you light soap like a candle

No, you cannot burn soap like a candle. Though some bar soaps look similar to candle wax, they are not the same and they behave differently when burned.

Unlike wax, soap simply has no wicking effect when it burns and while, if hot enough, you can burn soap away completely – it won’t burn with a wick gradually over time, it would simply auto-extinguish the flame. 

Is Dish Soap Flammable?

No, dish soap is not flammable by itself.

Though, in theory, it is possible for dish soap to trap flammable gas bubbles, so you might want to ensure you have wiped out any grease traps thoroughly before putting them back into use. 

Take a look at this:

Is Dove Soap Flammable?

No, according to Dove’s own safety sheet, Dove Soap is not at all flammable. 

What Is Soap Made Out Of?

In order to understand whether or not soap burns easily is to look at what soap is made out of. 

Soap is made by hydrolyzing fat (usually a sodium or potassium fatty acid) in a chemical reaction which is known as saponification

Thus, it’s made up of long chains of hydrocarbons with one end of the chain having a carboxylate group on it. 

When soap is added to water, the sodium or potassium ions of the carboxylate group separate from the chain and float free, which leaves the group with a negatively charged ion in water.

That was pretty sciency…

Essentially, soap is the salt of a fatty acid. 

How Does Soap Clean?

Soap is essentially a surfactant and something of an emulsifier (mixing agent). 

It works by surrounding other oil molecules and thus making them much simpler to remove by sluicing with water. 

This just means that soap will reduce surface tension and grab onto dirt and oil, which will allow it to be more easily washed off with water.

Is Lye Flammable?

If you decide to make soap at home, then you will almost certainly be using lye as an ingredient. 

(Lye usually refers to Sodium Hydroxide (NaOH))

Lye is very flammable as it can release a hydrogen molecule when heated. The hydrogen (H) released is quite flammable.

Lye is also particularly caustic (corrosive) and can burn your eyes, skin and even your lungs and respiratory system. 

So, it’s a good to take precautions when working with lye and not to keep it near open flames or your own body. 

The oils that you mix with the lye may also be more flammable than the end product that is your soap – so, more care is needed storing the raw materials for soap than the finished soap. 

Conclusion

Soap is not flammable. It can catch fire, but it has a high flash point and tends to resist burning in favor of melting thanks to the chemical structure of the molecules within it. Liquid soap may or may not be flammable, but it cannot usually sustain a flame, so there’s very little to worry about when it comes to it catching fire. 

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Chase

I have been a Firefighter in Northern California since 2012 and a Paramedic since 2008. My site is dedicated to helping answer questions people have about the fire service. I am passionate about helping to share what I have learned and assisting those who are pursuing a career as a firefighter. Thanks for coming to my site!

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