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Nerdy Science in the Kitchen

The Best Thermos Flask



With so many tumbler choices, you can't go wrong with the original thermos.
With so many tumbler choices, you can’t go wrong with the original thermos. The Thermos Stainless King at Amazon.

I remember being a kid and the best days were when my mom sent me off to school with Spaghetti O’s in my lunch box. They were in either a small red or blue thermos that resided in the wooden corner cupboard. I was definitely the cool kid in the school cafeteria with my plastic thermos and hot lunch.

Want the short version? I like the Thermos Stainless King at Amazon.

But I had never really thought about it; how do cold things stay cold and hot things stay hot?

The magic ‘thing’ that creates this strange occurrence is the vacuum, which refers to a space which is absent of air (no there is not a little vacuum cleaner running around in there). Remember in high school science class the terms convection and conduction? Heat transfers through air. Therefore, the absence of air prevents heat transfer. And for cold things, no there isn’t a little refrigerator in there. In the same manner, absence of air prevents the hot outside world touching the cold stuff you put into the thermos. Hot soup and cold drinks, all because of a space void of air. So simple, why didn’t I think of it?

Things to consider

Apart from price, there are a few things to think about when in the market for a thermos. In terms of material, most are made from glass, metal or plastic. Glass is easy to clean and retains its temperature well, but obviously is fragile. Plastic is the least effective in preserving heat. Metal is the most durable variety, and stainless steel is ideal as it will not corrode. Considering material, the stainless steel thermos is definitely the preferred variety.

The perfect thermos for you is out there! Check out my top picks.
The perfect thermos for you is out there! Check out my top picks.

Consider what you need it for and its volume. Do you like to make yourself a pot of coffee and sip on it all day? Maybe it’s for drinking on a cold cocktail at the beach. Thermoses come in all shapes and sizes, so consider the length of time and the amount of liquid you will be using it for.

Heat transfers the most at the top of the thermos, so the cap is an important consideration. Corks, valves and screw caps are the main varieties. Corks can leak and valves can deteriorate. The most functional type of cap is a screw cap.

Let’s look at some of the best options available out there.

Yeti Rambler is a 20 oz. Stainless Steel Tumbler

YETI Rambler 20 oz Stainless Steel Vacuum Insulated Tumbler with Lid (Stainless Steel)

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A thermos for drinking hot or cold drinks out of? No doubt about it, go no further than the Yeti. The Yeti Rambler is a 20 oz. stainless steel tumbler. This thermos is perfect for drinking on the beach. It keeps cocktails cold for hours. Couldn’t finish that last drink? It will still have ice in it in the morning (not that you would have a cocktail before noon…).

They come in a variety of colors, so you will not mix them up if drinking with friends. The ‘MagSlider’ that you sip from keeps the drink from splashing out. The only problem is that it retains heat so efficiently, that it takes a while for your coffee to get to a proper sipping level. The Yeti is a little pricey, but worth it if temperature retention is really what you are looking for.

Thermos Stainless King

Thermos Stainless King 40 Ounce Beverage Bottle, Stainless Steel

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For keeping food hot (or cold), a great option is by the founder itself, Thermos. The Thermos Stainless King offers a 16-ounce food jar. Bringing hot food to work? This product keeps food warm for up to 8 hours. Considering your lunch break is much sooner, no problem. Its design is extremely durable and great for hiking and traveling with no threat of cracks or leaks. Other sizes of this product are also available.

Thermos Work Series 40-ounce

Thermos Work Series 40 Ounce Beverage Bottle, Gunmetal Gray

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If you are in the market for a container to bring your pot of coffee, again, Thermos is the answer. (Looking for more coffee thermos options? Look no further). The Thermos Work Series 40-ounce product is a great durable product. There are several similar products by generic brands, but beware they may not have real stainless steel metal inside them. This product has a stainless steel interior and stainless steel cup which will not corrode. The rugged design makes this thing a tank, and the handle on the side make it a perfect product if you work outside.

Hydro Flask Sports Bottle

Hydro Flask Water Bottle - Stainless Steel & Vacuum Insulated - Wide Mouth with Leak Proof Flex Cap - 18 oz, Pacific

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Are you an athlete? Then you absolutely must have the Hydro Flask sports bottle. This product uses its TempShield technology, which keeps drinks hot up to 6 hours and cold for up to 24 hours.

You drink out of the Standard Mouth which is BPA free. The great thing about this product is its shape and design. It fits perfectly into a standard bicycle bottle rack and the coating is slip-free; perfect for sweaty hands. This product also comes in a large variety of fun colors.

The thermos – such a common household item yet underestimated in its design and function. Whether you want to have hot soup for lunch or a cold margarita at the pool, there certainly is a perfect thermos out there for your daily needs.

Looking for the perfect thermos for keeping food hot? Look no further.

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Image credit via Flickr Creative Commons: eiko and D. Coetzee

Kitchen Professor author
About the Author: David McLemore

David learned to cook at an early age after his mother told him that he couldn't live on pizza forever, Dave uses his modest kitchen skills to recreate sorely-missed recipes from home and to occasionally make new favorite ones from places he is visiting.

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