Wednesday, September 2, 2009

Thermos testing: Latte, home

At some point in the near future I plan on seriously investigating how viable portable coffee is. The kind you can make anywhere. There's a number of ways to do this these days. All of them require a source of hot water. Enter the Thermos.

The fact that the Thermos even exists, to me, seems to defy logic. What keeps the heat from leaking out (or in, for that matter) is there is the vacuum in between the outer wall and the inner wall. A freakin' VACUUM. How doesn't it just collapse in on itself? How hard does it have to hit something for the whole thing to implode? All these and more idiotic questions were probably answered some time in the late 19th century when Sir James DeWar invented the vacuum flask.

Vacuum flask. That's what they are called. Thermos is just one brand of them, but it has been adopted as the generic term for all vacuum flasks, in the tradition of rollerblades (Rollerblade is a brand of in-line skates), the lilo (an inflatable mattress), the walkman, and kleenexes, or "kleenices" to use the correct pluralisation. It turns out these are called genericised trademarks: trademarks that have lost their legal protection after becoming the generic name for a product or service. Wikipedia has an impressive list of them. Did you know that kerosene, cellophane, dry ice, escalator, and even HEROIN used to be trademarked? Wow. Imagine the legal complications if that was still around.

"One count of possession of a controlled substance with intent to sell. One count of bootlegging."

"Have you ever bought or rented a drug that wasn't quite right? It may have been a pirate copy, and illegal and inferior hit for which you paid good money."

"You wouldn't steal a handbag. You wouldn't steal a TV. Pirating Heroin™ is stealing. Stealing is against the law."

Anyway, back to the consumer vacuum flask. The contents can still reach equilibrium with the inner wall they are in contact with, so the wall material is made thin to minimise heat loss (or gain). Yet somehow it still doesn't implode. Also, heat can be lost through the opening, so the lid just has to be as insulated as possible. Would it be fair to say that because heat rises, storing the flask upside down would minimise heat loss even further? That will be the subject of another test. Today's test is simple. How well does a vacuum flask work?

If I want to be able to make coffee on a tram or in an elevator or something, I need to know my water is still going to be hot enough hours after I've left home. I swished some boiled water around in there, twice, to heat up the inner wall as much as possible, then poured in the very recently-boiled water, put the stopper on, and started the timer. Just for comparison I also set up a porcelain mug, and a paper cup with a plastic lid.

I'm glad I enlisted my nerdiest-looking thermometer for the job. So you don't have to squint, here's the results of the results:
  • The vacuum flask, not surprisingly at all, was the winner. After 20 minutes, the water was 96ºC. After 40 minutes, it was still 93ºC. After an hour, 92ºC. Take into account that I affected the outcome by measuring it. Three times. Also take into account that the water will be closer to 100ºC if I boil it on the stove instead of with one of those new-fangled electric kettlemajigs.
  • The mug was down to 54ºC after 20 minutes, while the paper cup was sailing along at 66ºC. Neither of them were much use after 40 minutes. But if you're letting your cuppa sit around for that long, you either forgot about it, or weren't really ready for one, or were willing to carry it around for a long time.
  • I remember in high school we did a similar test involving styrofoam cups vs paper cups vs mugs and found that styrofoam was a much better insulator. But I still don't like them, and I didn't have any around at the time so they didn't make the test.
  • This is about as far as I'm going with the temperature testing. While I am vaguely interested in how much a windy day affects the drinkable temperature window of a hot beverage, I'm not about to go sticking no temperature probe into no cappuccino. Taking photos of coffee in public is bad enough.

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