Vacuum insulated tumblers and water bottles are nothing short of modern miracles. Without any batteries, plugs, or refrigeration elements, they're able to keep hot drinks hot and cold drinks cold for hours, or even up to a day. You can pour hot coffee in one, and grab the outside without burning your fingers. Or fill one with ice cold water without worrying about condensation ruining your table.
But where did they come from, and how do they actually work?
The first ever vacuum flask was actually invented in 1892, by a Scottish scientist named Sir James Dewar. While performing an experiment on the element palladium, he required a container that would keep the metal at a specific temperature, and so he put a glass flask inside of another, larger glass container, and evacuated the air from the space in between, creating a partial vacuum.
Unfortunately, after enduring a long and bitter patent dispute against Alfred Nobel over a different matter, Dewar refused to patent his new invention, despite its commercial and scientific potential. In 1904, Dewar's own glassblower, Reinhold Burger, along with his business partner Albert Aschenbrenner, patented a metal version of the vacuum flask meant for home use, trademarked the name Thermos, and successfully fought off a later lawsuit from Dewar, who was never able to lay commercial claim to his invention.
How It Works
When you pour hot coffee into a cup, the outside of the cup heats up through a process called conduction. The molecules in the coffee have a lot of energy, which means they're moving very quickly, which we experience as heat. When those fast-moving molecules interact with the molecules making up the cup, they transfer some of that energy, causing the cup to get warmer.
Now say you put that cup inside a slightly larger cup, mimicking the design of a vacuum flask, but without removing the air molecules between the two layers. The heat of the inner layer would still eventually make its way to the outer layer by heating up the air molecules in the gap between the cups, which would in turn heat up the outside of the vessel.
But by removing the air molecules between two layers (i.e. creating a vacuum), there's no longer any pathway for the heat from the inner vessel to influence the heat of the outer vessel, since there are no air molecules to transfer any energy. On the flipside, the temperature of the air outside won't be able to influence the temperature inside the vessel, which is how your drink maintains its temperature.
In practice, obviously, Thermoses and other similar vessels don't have perfect vacuum environments, and the two layers still make contact with each other at the top of the vessel, and occasionally at other points inside for reinforcement, allowing for a small amount of heat transfer. But the effect is still good enough to keep beverages and foods hot or cold for most of a day.
Vacuum Insulated Products We Like
Vacuum insulated drinkware comes in every conceivable shape, size, and color, but these are some of our favorite products.
Thermos may not have invented the vacuum flask, but it's still been making them longer than anyone else. Their vacuum flasks come in all shapes and sizes, but we're particular fans of the brand's food jars. This one incorporates a folding spoon into the lid, and can keep soup hot for seven hours.
HydroFlask specializes in colorful, vacuum insulated drinkware for every occasion, but we're partial to the brand's clever wine bottle. Designed to hold the same amount of liquid as a bottle of wine, it's a great way to keep a bottle of white wine cold for a picnic, and really comes in handy in places where glass bottles aren't permitted. Naturally, the brand also makes vacuum insulated wine glasses to go with it as well.
While it's marketed for outdoor use, Miir's Camp Cup is essentially a lightweight (not to mention great looking) coffee mug that you could use at home or in the office. With its wide opening, it won't keep coffee as hot as a sealed travel mug, but it should give you plenty of time to finish your morning cup before it gets cold.
The brand makes a ton of other vacuum insulated gear that we love as well, so be sure to check out their whole storefront.
YETI obviously makes a ton of vacuum insulated drinkware, but one of our favorites is actually the most advanced koozie you've ever seen. It's perfectly sized for 12 ounce cans and longneck bottles, and will keep your drink cold for several hours.
Designed to hold 64 ounces of beer, the Stanley vacuum insulated tumbler can keep beverages cold for up to 24 hours thanks to its vacuum insulation and foam-insulated lid, which is a great touch. It's perfect for tailgating, and in our opinion, looks best in Stanley's iconic Hammertone Green.
A travel mug might be the first drinking vessel you touch every day, and a vacuum insulated one is great for sipping in the car on your way to work, without worrying about burning your fingers. Contigo's Autoseal West Loop will keep coffee hot for up to seven hours (or cold for up to 18), can be opened and closed with one hand, and features a lid that you can throw straight into the dishwasher.
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