When I ordered hot tea at a restaurant at lunch with one of my coworkers, the server brought a mug with “warm” water in it, several packs of honey, and a few lemon wedges. There was no tea bag. Right away I put honey in the water and squeezed the juice out of a couple of lemon wedges, and sipped. The water was not hot enough for decent black tea at that point. If I had waited for a tea bag, the water would have gotten too cold for making black tea.
As most tea lovers know, boiling hot water is necessary to brew black tea. You warm up the tea pot and tea cups to keep the tea as warm as possible.
But for Japanese green tea, depending on the grade of tea leaves and the kind of tea, lukewarm water can make better tea than hot water. The better the grade of tea, the lower the temperature of the water should be.
Sencha is consumed most commonly at home. The water temperature for regular grade Sencha should be around 90°C (194°F), and for the premium grade, the temperature 70°C (158°F).
Gyokuro, on the other hand, has a more delicate, mild taste. Delicate tea leaves need TLC – Don’t use water as hot as for Sencha. The regular grade would taste the best if the temperature is around 60°C (140°F). For the premium grade, the water temperature should be as low as 50°C (122°F).
I do not get Gyokuro tea leaves that often. But when I get even premium grade Sencha, I pour boiling hot water in a tea pot, and wait for a while until it cools down. When my palm feels the water has cooled sufficiently, I add the tea leaves to the pot. At lower temperature the tea tastes less bitter, and you can enjoy the delicate tastes of good quality tea.