I have been using a Chinese tea thermos for a couple of years, and I highly recommend them for good tea on the go. This type of tea thermos is quite common in China, carried around by workers as they go about their day, green tea readily at hand and replenished as necessary. I have also seen a few people with them in the United States. I personally would not use a plastic one, but the plastic ones are easier to find. The double-walled construction allows for holding the thermos comfortably, and insulates the tea from the cooler surrounding air. It has a metal filter that snaps into the interior and a screw-on lid. The devices are very easy to clean. The metal insert will get discolored from extended contact with tea, but it can be cleaned with vinegar.
The brewing of tea using this device is radically different from most other methods. One teaspoon of green tea is put into the thermos, the filter is put into place, water is added and then the tea is drunk directly from the thermos. Unlike in most other methods, the leaves remain in the tea as it is consumed, always considerably longer than a normal steep in a gaiwan or teapot. Throughout the day hot water is added each time more tea is desired. Obviously the primary difference in this brewing method is that the leaves steep for much, much longer than with other methods. I have found that the tea has a stronger taste, but does not get bitter.
In a glass tea thermos the tea should be somewhat delicate in taste, but also consistent and durable enough to hold up to long steeping times and multiple brewings. Chinese green, yellow and white teas are all suitable to this method, with varying degrees of success among individual teas. I have also had good results with lightly-oxidized Chinese and Taiwanese oolongs. It is important to brew the initial infusion with slightly lower temperature water, generally around 180 degrees, unless you like your tea very astringent in flavor, but I’ve found that in the subsequent infusions I can generally get away with hotter water because the leaves are already wet so they don’t get scorched.
Overall I like the thermos more than I expected to and get quite a bit of use out of it. It’s easily transported to and from home and work with or without tea in it. And one side benefit is that it displays the steeping of the leaves to great visual effect. It has made it possible to see clearly how differently shaped the leaves of the three Chinese green teas that I use most often in it look as they infuse.
Guest post provided by Cinnabar of Gongfu Girl. by