Saturday, May 28, 2011

Stainless Steel Thermos

I bring Limeade to work with me every day, mostly because I like to drink a hot beverage during the day, and coffee on a regular basis is a bit hard on my stomach.  I have bought and broken two conventional thermos bottles in a row because they are usually a glass inner bottle.  These are fragile, especially when they are filled with liquid.  There is nothing quite as disheartening as dropping a bottle in the parking lot, and when you pick it up, you hear a sound like rocks rolling around.

Unfortunately, I was not having much luck finding a stainless steel thermos bottle in local stores.  I am sure that it was there--but not at any store that I could find.  So I ordered this one online: the Thermos Stainless King.  It is indeed stainless steel inside and out.  It is probably less effective at keeping beverages hot or cold than the kind with the glass bottle (because metal conducts heat more effectively than glass), but so what?  Short of running over with a car, it is not going to break.  It was $23.37, and I suspect that one of my grandkids will use it some day.

UPDATE: For those that are curious, one of the comments explains in detail why stainless steel isn't a dramatic loss in insulation relative to glass because of the way that Thermos bottles work: essentially, they rely on a vacuum between the inner and outer layers, and only where the inner and outer layers meet is there much thermal conductivity.  Just a reminder, anytime you buy something from Amazon.com using one of my links to a product, it puts a few cents in my pocket.

3 comments:

Guffaw in AZ said...

I've had and used one for over 30 years...and it still works!
And very well insulated.
gfa

Mauser said...

Thermos stainless stuff is great. I spent $14 on a stainless Can Cosy (Which I haven't seen anywhere since) that keeps a can of Coke cold for a good three hours (if it lasts that long).

PhaseMargin said...

The thermal conductivity of glass is about 1.0 W/mC, while that of stainless is about 16 so yes, the stainless is less efficient. But when you compare stainless to something like regular carbon steel in the low 40s, aluminum at 250, or copper at 400 it isn't half bad.

The differences aren't too bad when you consider the construction of the bottle, too. The area between the walls is insulated, so the bulk of the heat has to flow out through a relatively narrow and thin opening, meaning that the thermal resistance is relatively high due to the configuration. You could probably make a high-carbon steel thermos work reasonably well, but stainless is better for having a lower reactivity with the various acids in foods.

I've had one of those stainless steel thermos bottles for at least 20 years now. I love it for bringing hot homemade soup to work. I highly recommend the zero points Weight Watchers veggie soup even if you're not on a diet, it's a regular feature of my lunch.