It is a going bit of advice in the tea world that if you are brewing a green tea (especially a delicate one) in a gaiwan to leave the lid off. The reasoning behind it is the heat from the steam will scorch the tea, similar to the effect of using water that is too hot. The real question is whether the affect of having slightly steamed tea is enough to affect the taste, and for that matter if the affect is negative or positive.
For today's testing I am using MeiMei Fine Tea Sichuan Mao Feng from last year, I was hoping to use this year's tea, but all my green's are stuck in postal limbo at the moment. For the brewing gear I am using my porcelain dragon gaiwan and a vintage porcelain cup. First session will be leaving the lid off except when using it to pour, next the lid will be left on during steeping but off between steeps, and lastly the lid will stay on for the whole session. The gaiwan and cups will not be pre-heated, which is standard for how I do tea in a gaiwan (unless it is clay.)
First up, the lidless brewing adventure! One thing I can certainly say for brewing in this fashion (other than I had to get my stubborn to cooperate and not leave the lid on) is you can really see the leaves dance, green tea is some of the prettiest to watch steep so it is almost a shame to lid it. The main difference between taste is sweetness. I find leaving the lid off the entire time (except while pouring) means that the tea's natural sweetness shines over the more savory notes. I also found that the flavor did not fade as quickly, so I could squeeze one more steep than usual out of it.
Next up I brew with the lid on, but take it off between steeps so the leaves don't get steamed like a pile of broccoli. And speaking of broccoli, leaving the lid on when the tea is steeping brings the vegetal notes, taking the sweetness and turning it savory. If you are a drinker of tea who dislikes the bittergreen aspect of some greens, this method might not be for you since I do pick up notes of kale and dandelion greens, I find it immensely tasty, but I know some people prefer their greens on the sweeter side.
For the last section of this test it was all lid all the time, the first steep being like the first steep of the previous section, more vegetal than without the lid but with a bit of subtle sweetness still. From the second steep onward the taste is just intense! Not only is the savory jacked up, so is the sweetness, it is savory and vegetal at the start with a touch of bittergreen at the middle and the finish is almost syrupy sweet. Also the color of the liquid is a lot darker, definitely a 'green' tea which was entertaining. The only real downside I could find to leaving the lid on at all times was the tea called it quits sooner, barely having any taste by the third steeping, with the most of the taste and body being in the first two. Which is fine if you are not having a lot of time for gongfu or just wanting a quick intense session.
So unless you are a person who really hates heavy vegetal notes or any bitterness at all I can see no real downside, however this is just one tea in a sea of hundreds (品茶图鉴 lists 136 Green Teas and that is not counting the random experiments farmers come up with) so the results can be vastly different from tea to tea, even harvest to harvest. Next week I am planning to compare green tea brewing in porcelain compared to a clay teapot, celebrating spring just a little bit more!