Does Coffee Evaporate or Just the Water?

crazy by Editorial Staff | Posted on February 3rd, 2023

Ever wondered what happens to your cup of joe when you leave it sitting out for too long? Does the coffee evaporate, or does just the water disappear?

This blog post will explore the complex question of whether coffee evaporates or just the water. Before delving into this topic, it is important to understand the basics of evaporation. Evaporation is essentially the transformation of a liquid into a gas.

Cup of coffee in a man's hand

It occurs when the molecules in the liquid gain enough energy to break away from each other and become vapor. Coffee, as well as water are both miscible liquids, meaning that they are capable of forming homogenous mixtures with each other.

As such, it is difficult to answer this question definitively. However, we can better understand the dynamics of coffee and water evaporation by looking at the scientific evidence.

What is Evaporation?

Evaporation is the process of a liquid turning into a gas. It is one of the most fundamental processes on Earth, and it occurs when molecules in a liquid absorb heat energy and disperse into the air as vapor.

This process is important for maintaining a stable water cycle and cooling us down when we sweat. Coffee does not evaporate as other liquids do, but it contains water that can evaporate. This is why roasting coffee produces rings of evaporated moisture around the beans.

The water in coffee evaporates at around 100 C but can also evaporate at any temperature from 0 to 100 centigrade, depending on the pressure. The evaporation front of coffee is unique because it requires water to escape from the outside layer of the bean first before it can reach the core.

Understanding this process can help us maximize the rate of evaporation of water from our coffee, ensuring that we get a delicious cup every time.

Does Coffee Evaporate?

Coffee does not evaporate, as it is not a liquid like water. However, the water contained in coffee does evaporate. This is because water has a lower boiling point than coffee’s other substances. When heated, the water molecules are activated and escape the surface of the cup, leaving behind the caffeine and other substances.

The evaporation rate is affected by several factors, such as temperature and pressure. Higher temperatures and lower pressures will increase the rate of evaporation. Additionally, the amount of surface area exposed to air also affects the evaporation rate. The more surface area exposed, the faster the water will evaporate from coffee.

Why Does Coffee Not Evaporate?

Coffee does not evaporate because it is mostly made up of compounds that are not volatile, meaning they are not easily converted into gas or vapor. The main components of coffee that do not evaporate are the oils, proteins, and carbohydrates that give it its flavor, aroma, and body.

Furthermore, caffeine is a relatively non-volatile substance, meaning it does not readily convert into a gas or vapor. When water evaporates from hot coffee, the other beverage components do not follow suit.

This is why when you leave a cup of coffee out for too long, it can become stale and flat-tasting; the flavor-carrying components stay in the cup while the water evaporates.

Isolated, metal thermos cup with tea or coffee on the table. The hot liquid evaporates.

What Happens When Water Evaporates from Coffee?

When water evaporates from coffee, the liquid gradually becomes a gas and leaves your cup. This process of evaporation forces water from a liquid into a gas, which can take some time, depending on the humidity in the room.

At the beginning of the roast, coffee is made of tiny granules of ground-up coffee beans suspended in water. During the evaporation process, these granules migrate to the outside layer of the bean, where they are exposed to heat and air, allowing for further evaporation.

As the water evaporates, it takes some of the essential compounds and flavors from the beans, leaving a more concentrated flavor profile. While this process can be beneficial for making some types of coffee, it can also lead to an overly strong cup that is too bitter or acidic if left to go too far.

Therefore, understanding the evaporation rate and how to maximize or minimize it is key to getting the perfect cup every time.

Factors Affecting the Rate of Evaporation of Water from Coffee

The water evaporation rate from coffee is highly dependent on external factors.

Temperature is one of the most significant factors, with higher temperatures leading to greater evaporation rates. In addition, the humidity of the air can play a role, as dry air will absorb more water molecules than humid air, leading to higher evaporation rates.

The coffee molecules’ size and shape can also contribute to the evaporation rate, with smaller particles evaporating more quickly than larger ones.

Finally, intermolecular forces can affect the rate of evaporation from coffee, with stronger forces causing molecules to be held in place more securely and thus leading to slower rates of evaporation.

All these factors can impact the rate at which water evaporates from coffee and should be considered when trying to maximize this process.

How to Maximize the Rate of Evaporation of Water from Coffee

One of the most effective ways to maximize the water evaporation rate from coffee is to take the lid off. This allows the water to escape from the outside layer of the bean first and also helps to reduce the amount of fat that can inhibit evaporation.

Fat is an insulator, so it can contribute to heat retention by coffee and make it more difficult for water to escape. Another way to maximize the evaporation rate is to increase the temperature of your coffee. Since water evaporates at around 100°C, raising the temperature will speed up the process.

Finally, stirring your coffee can help create more surface area for water molecules to escape from, thus increasing their chances of evaporating.


In conclusion, coffee does not evaporate, but its water content does. Water molecules move faster when heated, which makes evaporation happen faster. The soluble substances in coffee beans must be dissolved in water to release all their organoleptic properties.

Factors such as the size of the droplet, temperature, and relative humidity of the environment can affect the rate of evaporation of water from coffee. To maximize the rate of evaporation, one can increase the surface area of droplets, increase the temperature and reduce the relative humidity.


Editorial Staff

The editorial staff at Crazy Coffee Crave is a team of coffee enthusiasts & Baristas who enjoy the one thing we all think about as soon as we get up in the morning. Trusted by thousands of readers worldwide.