Daily Archives: April 7, 2012


We all know what a thermos is. It’s one of those things our mothers make us carry to school if we pack our own lunches – not to smother us but just to make sure we’re taken care of (her most precious child should not drink tepid milk or some other such thing). They’re like a thermal sweater for your beverage.

But if they’re the classic glass-lined kind, they’re a little fragile. I remember a few instances in elementary and junior high when my lunch box fell open and my thermos fell out – and the glass lining inside broke (possibly leading to sermons from my mother). That sure sucked.

Well, yeah. Vaccums suck. That’s what a thermos uses: a vacuum. Because you know what the best thermal insulator is? Nothing.

You need enough nothing to do the job, naturally. If you have no nothing between one surface and another, they can pass on their molecular vibrations to each other, and the heat normalizes. You need a space between them with nothing in it – no molecules. A vacuum. Then there’s nothing to communicate the vibrations. So heat doesn’t pass through.

Sound doesn’t, either – in space, no one can hear you scream (I’m sure we all know that the laser and other space sounds from most sci-fi movies are pure BS; the one movie I can think of that is true to the science is 2001: A Space Odyssey). Come to think of it, it would be nice if my downstairs neighbours were to surround their living (partying) space with a layer of vacuum – turn their apartment into a thermos. Their noise level kind of sucks.

You may be thinking, “Why isn’t he capitalizing thermos? It’s a brand name.” Well, yes, there is a Thermos brand, and they are the ones who applied the name thermos to vacuum bottles. Their website proclaims that they are the “Genuine Thermos Brand.” But the word thermos has passed into common usage for vacuum bottles. It is no longer protected as a trademark in Canada and the US (I’m less sure about Britain). Need further proof? The word thermos is in the Scrabble dictionary. You know that proper nouns are not allowed in Scrabble! (Which is why Zen is unplayable – it’s the name of a sect of Buddhism. Don’t get me started on all the places that one is used senselessly.)

Doesn’t it suck that Thermos don’t get the trademark protection on their brand name? Heck, even Aspirin is still protected in Canada (not in the US). This is why Caterpillar and Zamboni are so particular about how their brand names are used – they really don’t want what happened to thermos to happen to them. But there are a couple of things you should know about thermos that might affect how you feel about the matter.

First, and this might not surprise you, thermos is a word taken whole-cloth from Greek. The word θερμός thermos is Greek for “hot” (or “warm”). (Yes, thermoses can also keep things cold. In fact, as you will see shortly, that’s what they were invented for. All they do is greatly reduce the rate at which what they contain normalizes its temperature to the ambient temperature – they are not perfect because the inside of the vacuum bottle has to be attached to the outside and has to have an opening that can be unsealed to allow the contents ingress and egress.)

Sure, Caterpillar is a normal word and Zamboni a pre-existing family name. The trademarked use applies only to the product in question. But there’s more to know about thermos.

One thing to know is that another name for a thermos is a Dewar flask. Now, doesn’t that sound like a container of Scotch? But it’s not named after Dewar’s Scotch. It’s named after Sir James Dewar, the inventor of the vacuum bottle. He invented it because he was studying the optical properties of cooled liquids, and it made the liquids much easier to study for longer periods of time.

Dewar was one of the greats of 19th– and 20th-century English chemistry. He also co-invented cordite. He did much important work on the liquefaction of gases, including oxygen and hydrogen, but (due at least in part to a shortage of helium – the same thing that, decades later, led to the explosion of the Hindenburg, which had been forced to use hydrogen because the US wouldn’t sell helium to Nazi Germany) he was pipped at the post for the first to liquefy helium – and the guy who beat him, Heike Kamerlingh Onnes, later won the Nobel, a prize Dewar was nominated for several times but never won. Sucks, eh?

Dewar had the idea for the vacuum flask in 1892, and put it into use successfully. But he did not patent it. A German firm saw the commercial value in it, patented it in 1904, and gave it the name Thermos in 1907. Dewar sued for a share of the profits – but lost because he hadn’t patented it. Now, that sucks.

It’s also why you needn’t feel too bad about using thermos as a common noun. Sure, Thermos (the company) made the invention commercially available, leading to energy savings world-wide in keeping beverages hot and cold and reducing substantially the amount of tepid beverage consumed. But come on. Hardly right sporting, is it, to take someone else’s invention and patent it just because you can and then not give them a share of the proceeds. If they were to leave their invention in their unlocked garage, you would be arrested if you took it, even if you did something good with it.

Now, thermos is a nice name for it, that’s true. The therm is so soft and warm; it has good associations from other therm words, and it has that nice, light, cool dental fricative, a warm /m/ at the end, and in between a steady liquid, the syllabic /r/. And thermos is one easy word that has no other meanings.

But if you want to scotch that use, you can call it a Dewar flask. I’m not sure they’d let you take that to school, though.