UPDATED WITH PART TWO — ZOJIRUSHI
Vacuum bottles die. You drop or dent one, next thing you know your coffee is lukewarm when you need it hitting your tongue like a Baja sunrise. The other day I went through our bottle stash, tested our smaller thermoses, and not one of them worked (due to getting beat up and damaged over months and years). Figured that made for a possible review of some new acquisitions. Rather than search far and wide for bottles, I donned my everyman shopper hat and simply bought two of the easiest to find at my favorite etailers. My shopathon had simple criteria. The vacuum bottles needed a cup-cap, good reputation, and be around half a liter in capacity.
Testing these things is easy. Just pre-heat equally, fill, and measure temps a few times over a long enough span to see some differences. While both bottles held heat enough to remain pleasantly hot over your basic 4 to 7 hour ski tour, I was surprised to find the Stanley falling behind by several degrees after 4 hours, and coming in about 7 degrees behind after 10 hours. Strange because the larger the thermos bottle the less surface area per unit volume, and it’s thus potentially more efficient. The difference could be because the Stanley has a larger-longer neck under the cap (that area is relatively uninsulated in both units), or it lacks good reflective coatings on the internals to prevent radiant heat loss.
The Stanley weighs 410 grams, 14.42 ounces, and the Thermos brand bottle weights 332 grams, 11.6 ounces while holding just 2 fluid ounces 50 ml) less tea. To me the case is clear, I’ll favor the Thermos brand bottle: a few ounces less weight and a few degrees warmer tea. (I measured capacity with a measuring cup; published specifications may be slightly different.)
Shopping for vacuum bottles is tricky. Every factory in China must be making them — with quality all over the map. More, many of them appear to be sold under different brand marks. I could be wrong, but I’m thinking by purchasing the branded Thermos option you get better odds of it lasting and holding heat. I got mine on Amazon (same item as link to right), please comment on other sources, models and brands if you’ve found something that works well.
Other thoughts: The Stanley appears to be less prone to damage (reason for some of the added weight). Both might have warranties that would be useful if they stop working correctly, you never know till you try.
Part 2: Zojirushi
Thanks to our terrific WildSnow commenters, I got my attention directed to the Zojirushi vacuum bottles. So I ordered up the the 500 ml and the 350 ml little guy off Amazon (see links below). The 500 is noticeably lighter than the Thermos brand of same volume (apparently there are two models/weights of the 500, I got the lighter one). Metrics: Zojirushi 500 ml masses at 278 gr (9.8 ounces), that’s nearly two ounces less than the Thermos brand bottle of the same volume. Surprising. Zoji is also shorter, with virtually the same diameter (differences in vacuum spaces and such probably allow smaller dimensions.) I’m not sure I’m convinced on the Zojurushi mechanical pour stopper-cap. It’s kinda’ techie cool, but probably not the thing you want on an expedition when small gear failures create big consequences. For day ski-tours, however, the mechanical cap is convenient and holds in heat as opposed to removing a screw plug-cap. Note the Zoji bottle does not have internal cap threads, so you can’t swap on another stopper.