Can You Put a Stainless Steel Thermos in the Freezer?

Can You Put a Stainless Steel Thermos in The Freezer

The stainless-steel thermoses are familiar products, very suitable for office workers, students or families with young children. The thermos is excellent at heat retention, compact and easy to use. However, if not used and stored properly, the thermos is also very susceptible to damage, reduce its function, but more seriously, adversely affect health. Let’s find out how to use a thermos safely. Should you put a stainless-steel thermos in the freezer or refrigerator?

Can you put a stainless-steel thermos in the freezer?

A thermos is a product capable of keeping both cold and hot water for a long time. The bottle is designed to be quite compact with a 3-layer structure: the inner layer, the vacuum layer and the outer shell. In particular, the inner layer and the vacuum layer will directly affect the ability to retain heat as well as the quality of the drink.

You should not put the stainless-steel thermos in the freezer. If being frozen, the liquid inside the bottle will expand when it is cold, then deform the bottle, affect the inner layer and the vacuum layer. As a result, the thermos reduces or loses the heat retention efficiency, and it will no longer insulate properly.

To prolong the product life, the stainless-steel thermos should not be kept in freezer.


Contigo AUTOSEAL West Loop Vacuum-Insulated Stainless Steel Travel Mug
Contigo AUTOSEAL West Loop Vacuum-Insulated Stainless Steel Travel Mug



Is the thermos safe?

In terms of physics, the thermos can cause explosions, sudden bursts due to increased pressure when containing too hot water. Sudden temperature changes also have a negative effect on the thermos. However, you can rest assured because now the bottle has been improved with many modern features, minimizing problems when using.

In terms of chemistry, there are questions like: Is storing water in a thermos harmful to health? Does the bottle contain toxic substances dissolved in water that are harmful to users? This is a concern of many people, especially when there has been a recent incident of poor quality thermos.

To avoid buying the poor quality thermos, you need to choose the reputable brands. Also, pay attention to the information about the product to choose the best one.

Stanley Classic Vacuum Food Jar
Stanley Classic Vacuum Food Jar

Can you keep food hot in a thermos?

Thermos bottles for food are specialized for storing different dishes, so the design is usually lower but wider than a normal one. The bottle mouth is often wide, and the lid is attached with a spoon convenient for preserving food for people at work or at school.

It is safe to keep food hot in a thermos. However, the thermos can only keep food hot or cold when it has some sauce or liquid. It can keep food hot for many hours. Besides, you can use a thermos to store beverages that need to be kept hot like coffee, tea or cold like milk, pure juice.

Zojirushi Ms. Bento Stainless-Steel Vacuum Lunch Jar
Zojirushi Ms. Bento Stainless-Steel Vacuum Lunch Jar

How to use a stainless-steel thermos safely

Clean the thermos before use

Before using for the first time, clean it (including the body and lid) with dishwashing liquid or hot water, or vinegar to deodorize the bottle. Thus, when using a thermos, it will not affect the taste and quality of the water used, then let it dry and install the accessories in the original position.

Before each use, you should rinse the bottle with hot or cold water for about 2 minutes to heat or cold the bottle for the best heat preservation effect.

Use the thermos with the heat preservation function correctly

Thermoses usually have a 2 or 3 layer structure. You need to check whether the structure of the bottle is dedicated to keeping cold only or can store both hot and cold drinks, to ensure the effectiveness of keeping heat.

Do not overfill the water

Do not fill the thermos with too much or too little water, the ideal water level is about 2cm below the neck of the bottle.

If it is too full, water will splash out when the cap is screwed on, resulting in burns. If the water is too little, the heat retention efficiency will be reduced.

Close the lid carefully

After adding water, tighten the lid of the jar clockwise to prevent water leakage.

Pay attention to the temperature

With hot-cold thermos flasks, some products have a limit of heat resistance below boiling point, at about 70 – 80 degrees Celsius. Therefore, care should be taken to avoid storing water that is too hot, which may cause damage to the flask or react with the bottle surface material to produce harmful substances.

Be careful when converting hot to cold or vice versa

During use, if you want to switch from keeping hot to keeping cold drinks or vice versa, first put cold or warm water into the jar and wait 2-5 minutes and then pour it out.

If you plan to switch to cold water, rinse the jar with cold water for about 2 minutes to chill. If you are switching to keep hot, rinse the jar with hot water for about 2 minutes to warm up. Then you can be assured of the effectiveness of keeping the bottle hot or cold.

Finally, after putting the drink in the bottle, it is necessary to check that if the lid is tightly closed to avoid water leakage when moving.

Choose the reliable brands

To use it safely, you should choose a thermos from reputable brands. According to the experience of many users, you should buy products with thick insulation and shiny metal housing.

The plastic lid that is made from Primary plastic will not cause an unpleasant smell when it is hot.

Further reading:  Best Mini Fridges for College

Tips to properly store the stainless-steel thermos

Avoid strong impact

You should avoid strong impact on the bottle. Too strong a force will cause the two metal layers to touch each other, reducing the space between them, leading to a decrease in the insulation of the thermos.

Do not let the temperature change suddenly 

You should leave a “breathing interval” between hot and cold for the thermos. If you are storing cold water and want to switch to hot water and vice versa, you need to leave the thermos with a gap of about 3-5 minutes. The sudden change in temperature will cause the material in the bottle to expand and contract suddenly, reducing the bottle life.

The thermos needs a breathing interval between hot and cold
The thermos needs a breathing interval between hot and cold

Regular cleaning

You need to clean it regularly to avoid mold and bacteria accumulation. Never use strong detergents, corrosive solutions (bleach, acetone, etc.) to clean the thermos.

When storing ordinary filtered water, just clean the bottle with dish-washing liquid and left to dry naturally. After storing other drinks that retain odors and keep other residues, you need to clean the bottle more thoroughly so as not to mold, breed bacteria that may affect the next use.

Do not put it in the fridge or freezer

Do not place the thermos in the freezer or refrigerator, because the liquid in the bottle will expand when it is cold and deform the bottle, reducing or losing the heat retention efficiency of the thermos.

THERMOS Stainless King Vacuum-Insulated Food Jar
THERMOS Stainless King Vacuum-Insulated Food Jar

Do not put it in the microwave

Microwave ovens can explode if you put metal objects inside. So, if you want to warm up a drink, pour the water into a ceramic or heat-resistant glass (make sure it is microwaveable) and then put the glass in the microwave.

What thermos keeps water hot the longest?

Stanley Classic

It is a bit heavier than some of the similar ones on the market, but there are many reasons why Stanley has been used for generations. The handle on the side makes it easy to carry and pour, even when you are wearing gloves.

The lid functions like a cup, so if the drink is too hot to drink directly from the thermos, you can pour it over the lid to cool it down faster.

Stanley trademark has been a leading candidate for a thermos since its release in 1913. There have been updated design since then. The Stanley classic vacuum insulated thermos can keep liquids hot or cold for over 24 hours.

Contigo Byron Thermal Travel Mug

The best low profile coffee thermos can work well on the hiking trail. Unlike standard travel coffee mugs, the Contigo Travel Mug is designed with a SnapSeal lid that seals leaks and keeps coffee hot for longer.

Contigo comes in 16, 20, and 24 ounce options. And it also gives you the option of a handle, a handle, or no. The high-quality stainless steel body is BPA-free and insulated well enough to keep liquids warm for 7 hours and cold for 18 hours. 

Zojirushi SM-TA48BA

Because it’s built to exacting specifications, the beauty is in every detail with the SM-TA48 Stainless Cup. The double-layer design is coated on the inside with a non-stick coating for easy cleaning and protection against corrosion.

The cleverly designed and easy lid is a favorite for users, opening with a two-step release that locks tightly for easy sipping. There’s also a safety lock to ensure that your hot drinks are always where they’re supposed to be.

Hydro Flask Standard Mouth Bottle

Standard Mouth Bottles are available in different size and with the same TempShield insulation construction as the Hydro Flask Food Containers. However, you will not have the built-in cup that some other thermos does.

Whether it’s cold water or hot coffee, Standard Mouth Bottle does its job of keeping heat well. We believe this is one of the better thermos options for those who want to take it with them when hiking or day trips. This Hydro Flask standard mouth bottle can keep beverages cold up to 24 hours and maintain hot water up to 12 hours.

THERMOS Stainless King

Thermos Stainless King is designed to act as a holder for hot or cold liquids. Vacuum insulation helps keep liquids hot or cold for 24 hours.

The Thermos King’s lid functions as a cup. To make pouring easier and maintain liquid temperature longer, Thermos has integrated a spout and a smart screw that allows you to pour liquids without removing the stopper. This thermos is a good option as it is easy to use, BPA free and dishwasher safe.

MAXSO 2 pack soup thermos for kids

The Maxso thermos is the perfect companion for lunches with soups. The size and function of each can help you confidently stash these anywhere in your backpack or lunch box. They are vacuum insulated to keep food hot for up to 12 hours and cold for up to 24 hours.

The top lid acts as a bowl for eating, and the air-tight lid helps keep the food inside the thermos. With an updated design, the collapsible spoon fits snugly with the tight-fitting lid. The containers have a non-slip bottom and an easy-to-open air pressure system that even your kids can get used to.

Takeya Insulated Water Bottle for Kids

If your child needs a new thermos for school, the Takeya Insulated Water Bottle is an extremely handy design. This durable bottle comes in both 14 and 16-ounce versions. So, it is small enough for kids to easily hold and carry.

It is useful for keeping liquids cold for hours and your child won’t have to worry about opening and closing the lid since it has a built-in straw. The straw makes it easy for children to drink without tilting.

Plus, this bottle comes with a sturdy attachment point that can easily clip onto a backpack. The only downside to this type of insulated pitcher is that it’s only for cold drinks. You can not use it for hot liquids.


To be safe, the stainless steel thermos should not be kept in the freezer. In addition, you should also apply the tips when using and storing the thermos.

Thermoses from reputable brands, as suggested above, are worth buying. They are perfect choices for keeping drinks and food.

Jenny Brown
Hi, I’m Jenny. On my blog, you will find helpful advice about using and organizing the kitchen appliances. You will also receive the recommendations on choosing a compact refrigerator or freezer that best fits your demands. Besides, frozen meals from the freezer bring many incredible benefits because they ensure freshness, deliciousness, and full nutrients. Many helpful tips from experts on frozen meals will also be found.