Can Coffee Get Hotter In A Thermos?

Have you ever made coffee in your thermos, and an hour later, you take a sip and burn your tongue? Most people have. While you struggle through the day with a raw tongue, one may wonder if coffee can get hotter in a thermos or if a thermos is just good at regulating the temperature of the coffee inside.

A thermos is a good insulator for keeping hot drinks hot and cold drinks cold, but it cannot increase the temperature of your coffee and make it hotter. A thermos cannot increase the temperature of your coffee, and the temperature will slowly decrease as a thermos is not a perfect insulator.

We all enjoy a hot cup of coffee from a thermos in the cold weather. Sometimes when we pour that first cup of coffee, it seems much hotter than when we first filled the thermos. Is this phenomenon a reality, or is it simply perception that causes us to feel that the coffee has increased in temperature in the thermos?

How A Thermos Works To Keep Coffee Hot

The thermos design enables it to regulate the temperature of the coffee inside it, but coffee will not get hotter in a thermos because there is no heating element in a thermos. A thermos is a unique container that keeps your coffee hot or cold for a couple of hours, and depending on the type of thermos you have, the time related to your coffee remaining hot will increase.

Hot mediums become cold by transferring heat to the surrounding objects, and cold mediums become hot by absorbing heat from the surrounding things. The design of a thermos is to keep hot coffee inside and retain as much heat as possible, ensuring the coffee stays hot over a certain period.

By pouring hot coffee into your thermos, you are now entering into an area in which the design of a thermos is to store the rich aromas of freshly brewed coffee that is ready to drink on demand throughout the day without having to go through the hassle of brewing another cup of coffee.

Its flawless design ensures the coffee remains hot and tastes fresh during the day. To visualize how the science behind a thermos works, watch this video below.

How Long Does Coffee Stay Hot In A Thermos?

When purchasing a thermos, the goal is always to keep your coffee hot for a long time. It is essential to look at build quality as a determining factor to how durable and reliable it will be no matter the time, temperature, and environment you use it in.

The thermos you buy will directly affect the time it takes for the coffee inside to start to cool down. It is essential to understand a thermos that uses higher quality materials will be able to retain heat for longer compared to a thermos made of less expensive materials like plastic.

The average time that coffee can stay hot in a thermos range is between 5-24 hours. A thermos made of stainless steel and vacuum insulated can keep your coffee warm for up to 24 hours due to the stainless-steel body’s ability to retain heat better than materials like plastic or glass.

Most thermoses fall under this 24-hour window mainly due to build quality and the materials used to make these thermoses. When considering how long coffee can stay hot in a thermos that falls into a category where materials such as plastic and glass are primary, the average time you must keep in mind will range between 5-12 hours, respectively.

How Do You Keep Coffee Warm In A Thermos?

Enjoying a warm cup of coffee is one of the most satisfying experiences anyone can have at any given time of day. With a thermos, when used correctly, you can keep coffee warm for longer without having to heat the water before enjoying a cup of coffee.

Using your thermos is vital in ensuring that the once boiling water will remain warm for extended periods. As soon as coffee is made and poured into your thermos, ensure the lid is on and sealed properly to prevent heat from escaping.

A thermos is designed for one reason only: you only have to brew coffee once and enjoy it while it’s still hot hours later. If the lid of your thermos is not airtight, the heat will escape, and your thermos will not be able to keep your coffee warm for long.

Keeping the lid on your thermos when you are not pouring coffee will ensure heat retention in the coffee. It is essential to know that when the lid is not on the thermos while you are enjoying a cup of coffee, the heat from your freshly brewed coffee will escape and cause the coffee to become cold and unenjoyable.

How Do You Make Coffee In A Thermos?

There are many ways to make a good cup of coffee, but as you know, the possibilities are endless. Making coffee in a thermos can be tricky and somewhat challenging if you don’t know-how. Everyone has their own idea of a good-tasting cup of coffee.

Firstly, while your coffee is brewing on the side, you have time to pre-heat your thermos. So, ensure you take the remainder of the boiled water still in the kettle and pour it into your thermos. The warm water will heat the thermos and create a space for the freshly brewed coffee to be kept warmer for longer.

As soon as your coffee is brewed and ready to be poured into your thermos, make sure you empty the thermos of the hot water and start pouring your coffee into your thermos. Note that the thermos will lose heat as soon as the hot water is poured out due to the lid not being on and sealed tight, so be sure not to linger on this step.

We all know that not everyone enjoys freshly brewed ground coffee. But fear not; your thermos accommodates instant coffee as well. First, heat your thermos with some warm water. The moment it is pre-heated, be sure to empty the thermos of the warm water, add your instant coffee and milk if you like, close the lid to create an airtight seal, and your coffee is ready to go.


The design of a thermos is to make sure you have a hot and enjoyable cup of coffee any time of the day. By looking at how to utilize a thermos to brew coffee and keep it warm for up to 24 hours, it is safe to say that this is a magnificent design.

The design elements of a thermos are not to generate heat on their own and, therefore, keeps your coffee hot for extended periods but cannot increase the temperature of the coffee.


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