cooking oil

Can cooking oil evaporate? We found out the hard way

You’ve probably boiled water hundreds or even thousands of times and one thing you’ve noticed is that at a certain temperature, water boils. Bubbles begin to rise and pop out of existence. It follows by with this visible mist right before our eyes.

But when you cook oil, you don’t get to see it like that. No matter what temperature you set your stove to or how long you’ve left it on the burner, it doesn’t seem to fill the air with the misty texture of steam from water.

You can easily see water evaporate, but you can’t seem to replicate that with oil.

So the question begs, can cooking oil evaporate?

Cooking oil close up
Cooking oil close up

Generally speaking, yes and no. The chemistry behind the difference between cooking oil and water lies in the molecular weight of the compounds that make up oil. Typical cooking oil molecules are heavy compared to water. It’s for this very reason when heated to a certain degree, the heat will break apart its molecular structure, cause it to decompose, and become black smoke. However, oils do evaporate when left alone, but it can take months to even years.

Let’s talk about how oil would evaporate in normal conditions.

How long does it take for cooking oil to evaporate?

To better understand how and when oil evaporates, we must first understand 2 categories of oils. One is named volatile oils and the other is called fixed oils.

Volatile oils come from mainly plants and their leaves, roots, petals, and bark. These are considered essential oils. These oils will often evaporate fully and completely.

This can usually take several days and even weeks to occur. The evaporation process usually results in very little to no residue left.

These types of oils are mainly used in perfumes.

As for fixed oils, these are usually considered our cooking oils. Fixed oils contain a much higher concentration of fatty acid and glycerin. The major source of these oils comes from seeds and when it evaporates, it does so leaving behind a sticky residue.

The process of evaporation for fixed oils can take months to even years.

Does oil evaporate at room temperature?

The short answer is yes. But it’s a little more complicated than that. Oil can evaporate at room temperature, but only until the concentration of gaseou oil and liquid oil is in equilibrium.

What causes oil to evaporate?

Generally speaking, the main reason why oil, or any other liquids for that matter, evaporates is due to kinetic energy.

I think this video gives an amazing explanation about how evaporation, in general, works.

Think about molecules. It’s always moving even within oil. Now, the degree of evaporation is mainly a result of the distribution of speeds that a molecule inside a substance like oil has.

Molecules that move really fast has a more likely chance of leaving the liquid phase as gas.

One thing that plays a big role into the rate of evaporation is the weight. Oils, compared to plain water (H2O), are made up of large molecules. There are tons of carbon chains linked together to make oil.

What is the boiling and smoking temperature of cooking oil?

The exact boiling point of oil really depends on the purity of the oil itself. Typically speaking, palm cooking oil, which is considered 100% fat, is estimated to boil up to as high as 300°C (572°F).

However, well before oil boils, it firsts goes through the smoking phase. The smoke point is a measure that’s almost exclusive to oils and this may sometimes cause your food to have that burnt flavor.

Cooking OilsSmoking Points
Olive oil190°C (375°F)
Canola oil205°C (401°F)
Sunflower oil225°C (437°F)
Peanut oil250°C (437°F)
Corn oil230°C (446°F)
Palm oil235°C (455°F)
Soybean oil257°C (495°F)
A small list of common cooking oils and their smoking points

What happens when oil evaporates?

It could take a really long time for oil to evaporate. But in regards to cooking oil, when it evaporates it leaves behind a varnish or residue. This residue ends up staining almost anything it touches.

You can actually see these varnish stains left over on the pots and pans in your own home. The varnish in pots and pans don’t happen by normal evaporation. These were accelerated by heat. But the basic idea is still there.

Does frying oil evaporate?

Again, let’s go back to the idea of kinetic energy. Now, kinetic energy is proportional to its temperature. Higher temperatures will cause molecules within the oil to move faster and potentially allow it to break free from the hoard.

So the answer is yes, frying oil does cause the oil to evaporate to a certain degree. However, exclusive to oil and fat is the smoking point.

During cooking, the oil will smoke long before it actually evaporates. This is when instead of simmering over a hot flame, the oil will let out some serious smoke after reaching a certain temperature.

Be wary, the oils can reach a certain temperature in which they go into something called a flashpoint. At this point, you need to know that it can produce ignitable gas. Don’t let it get to this point.

Related Further Reading:

Luckily for me, my oil had only gotten to the point of smoking and that’s when I cautiously turned off the stove and kept an eye on it until it settled down.