Why Does Coffee Get Cold?

crazy by Editorial Staff | Posted on March 31st, 2023

As a coffee lover, have you ever wondered why your favorite beverage gets cold quickly? In this post, we’ll explore that question.


Importance of temperature in coffee

Studies show that temperature is a critical factor in coffee brewing. Some ways in which temperature affects coffee include:

coffee

Extraction

The temperature of water used for brewing coffee determines how much flavor is extracted from the beans. Water that is too cold may not extract enough flavor, while water that is too hot may extract too much, resulting in a bitter, over-extracted brew. 

According to the U.S National Coffee Association (NCA), the optimal temperature for coffee extraction is considered to be between 195°F and 205°F (90°C to 96°C). If the temperature of the water used for brewing fluctuates, it can result in uneven extraction and a variation in the taste of the coffee.

Roast level

The temperature of the water used for brewing can also affect the perceived flavor of the coffee. Darker roasts may taste less bitter when brewed with slightly cooler water, while lighter roasts may require hotter water to extract the optimal flavor.

Brewing method

Different brewing methods may require different water temperatures. For example, pour-over methods typically require hotter water to maintain the ideal brewing temperature throughout the brewing process.

In comparison, immersion methods like the french press may require slightly cooler water to avoid over-extraction.

How heat transfer in coffee works

Heat transfer is exchanging thermal energy between objects or systems, resulting in a temperature change. Five modes of heat transfer relate to coffee:

Conduction

Heat transfer in coffee through conduction occurs when the coffee comes into contact with a surface that is cooler than it is.

When hot coffee is poured into a ceramic mug, the heat is transferred to the mug through conduction. As the heat is transferred, the temperature of the coffee begins to decrease. 

Similarly, if you touch a hot cup of coffee, the heat is transferred from the cup to your hand through conduction.

Convection

Heat transfer through convection occurs when a fluid, such as air or water, circulates the coffee and carries away the heat. When you blow on a cup of hot coffee, the air movement carries away some of the heat from the surface of the coffee, which can help to cool it down faster. 

Radiation

Heat transfer through radiation occurs when heat energy is emitted through electromagnetic waves. The heat from a hot cup of coffee can be radiated out into the surrounding environment, which can cause the coffee to cool down faster. 

Evaporation

Evaporation occurs when water molecules in the coffee become vapor and escape into the air. This process takes heat energy from the coffee and cools it down. 

In a hot environment with low humidity, evaporation happens more quickly and can lead to faster cooling. This is why leaving a cup of hot coffee out in the open air can cause it to cool down more rapidly than if it was covered or in a sealed container.

Insulation

Insulation works by reducing the rate of heat loss from the coffee to the surrounding environment. This is achieved using materials with low thermal conductivity, such as foam insulation, which creates a barrier between the coffee and the external environment.

Factors that affect the cooling rate of coffee

Altitude

At higher altitudes, the boiling point of water decreases due to the lower air pressure, which means that coffee brewed at high altitudes will be cooler than coffee brewed at sea level, even if it was brewed at the same temperature. 

The lower air pressure can cause coffee to lose heat faster, which means the coffee will cool down faster at higher altitudes.

Type of brewing method 

For example, drip coffee brewed with a paper filter tends to cool down more slowly than coffee brewed with a metal filter or a French press, as the paper filter helps retain some heat. 

Similarly, espresso-based drinks tend to cool down more quickly than drip coffee due to their smaller volume and higher surface area exposed to the air. 

Volume of coffee

The volume of coffee in your cup can affect how quickly it cools down. A larger volume of coffee will cool down more slowly than a smaller volume because there is more heat to dissipate.

Additionally, it’s important to note that the shape of your cup can also impact the cooling rate. A cup with a wide opening will cool down faster than a cup with a narrow opening because more surface area is exposed to the air.

Tips on keeping coffee hot

If you notice your coffee gets cold quickly and want to stay hot for extended periods, here are some tips that will help.

Preheat your mug

Preheating your mug or thermos is a simple yet effective tip for keeping your coffee hot longer. 

When you pour hot coffee into a cold container, it can cause the temperature to drop quickly. Preheating your mug with hot water before filling it with coffee can help maintain its temperature. 

Use a cozy

A coffee cozy or sleeve can be a simple and effective way to keep your coffee hot for extended periods. These sleeves are usually made of insulating material and are designed to fit snugly around your coffee mug, helping to trap the heat inside. They are available in different materials, including silicone, neoprene, and felt. 

Additionally, some coffee shops offer reusable sleeves you can purchase and bring each time you buy a cup of coffee. Using a coffee cozy can also protect your hands from the heat of the mug.

Consider using a portable coffee warmer

Portable coffee warmer can be a convenient option for keeping your coffee hot, especially if you are on the go or at your desk. 

These small devices are designed to sit on your desk or tabletop and plug into a power source. They have a heating element that warms up the base of your coffee mug, helping to keep your coffee hot.

Some portable coffee warmers also have temperature controls to adjust the heat level. 

Types of coffee mugs and insulation

Ceramic mugs

Ceramic coffee mugs are popular among coffee drinkers due to their style and insulation properties. They are typically thick-walled, which helps to retain heat and keep your coffee hot for longer periods.

However, not all mugs are created equal in terms of insulation. Some are thinner or have a smaller capacity, impacting their ability to maintain temperature. 

Vacuum-insulated stainless steel mugs 

Vacuum-insulated coffee mugs are designed to provide maximum temperature retention, making them an ideal choice.

These mugs usually come with a lid that helps to prevent spills and retain heat. Some mugs also have additional features, such as a non-slip bottom or a handle for easy carrying. 

However, these mugs can be heavier and bulkier than other coffee mugs, which may not be as convenient for some coffee drinkers. 

Silicone coffee mugs

The vacuum between the inner and outer walls of the mug reduces heat transfer. The mugs are a lightweight and convenient option for coffee drinkers who are on the go. 

In terms of insulation, these mugs are typically single-walled, which means they are not as effective at retaining heat as vacuum-insulated mugs. 

They are also microwave-safe, making reheating your coffee easy if it cools down.

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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.