How to Choose a Thermos

When you were a kid, a thermos was an essential part of your lunch box and often contained soup or hot chocolate. Now that you're older and have replaced a day at elementary school with a day in the mountains, a thermos should still be a carrier of comfort foods and drinks as an essential part of your hiking BACKPACK.

Modern thermoses are lightweight but still do an incredible job of retaining a liquid's temperature, whether it's hot or cold. You can use thermoses in the summer to keep water, lemonade, iced tea, or any other beverage cold, giving you a refreshing break from the heat.

More often though, you'll see thermoses used to keep a wide range of liquids hot. Whether it's soup, tea, or coffee, having a warm drink while hiking or snowshoeing in the wintry weather can make your outdoor experience that much more enjoyable.


Most thermoses you'll see today are made of stainless steel, making them easy to clean and giving them solid durability. While other beverage holders made of durable plastics could probably take a hit better than stainless steel, which can dent, they don't have the insulating properties of stainless steel thermoses. Steel also does not retain tastes and odors.

The earliest thermoses were built with glass linings, which, although they worked well to maintain a liquid's temperature, weren't a great piece of OUTDOOR GEAR and came with the added risk of shattering. The vacuum-packed barrier was known to implode when the thermos was given a strong bump, which not only affected the durability of the thermos, but also the safety of its user.

A stainless steel design also keeps any chemicals from leaching into your liquid, unlike some plastics that have been known to emit harmful chemicals like Bisphenol A (BPA).


So we know that thermoses keep cold beverages cold and hot beverages hot, but how does that work? Thanks to a 1913 invention that proved steel can insulate as well as glass as long as it was constructed properly, we were given the double-wall construction method. Now, 100 years later, we still use double-wall construction that does a fantastic job of keeping liquids at their proper temperature.

The system works by using two layers of steel to create a vacuum that helps eliminate the two major methods of heat loss: conduction and convection. This gives these thermoses excellent temperature retention by keeping out whatever the ambient temperature is, and holding in the liquid's temperature.

Backpacking and Hiking

Thermoses are excellent for backpacking and hiking, because at the end of a long day, there are few things better than unloading your CAMPING GEAR and enjoying hot soup, chili, or a beverage. Some thermoses can retain the temperature of liquid for as long as 24 hours, making them ideal for overnight trips or full-day excursions. Many stainless steel thermoses are sleek in design and can be easily packed, keeping weight and bulk to a minimum.

Thermoses are easy to clean—always a plus for any camping or hiking gear—and come in different sizes and capacities, ranging from half a liter to a liter, or about 16 to 33 ounces.

Keep in mind, though, that the outside appearance of a thermos may be deceiving. Because of the double-wall construction, capacity will likely be less than it appears from the outside. Be sure to check the thermos's capacity, and choose one that’s suitable for your needs.

Whether it's to keep a lemonade treat cold for the end of a hike or to keep a coffee pick-me-up warm midhike, thermoses are ideal for adding that extra luxury on any outdoor adventure.