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How to Brew Green Tea - The Top Ten Reasons Your Tea Didn't Turn Out Good
You brewed it too hot. If you brew it too hot, it will become bitter. This is probably the most common of all mistakes and one which has the most influence over the taste. Depending of the variety of green tea it should be brewed around 175 degrees F (79 C) give or take 5 degrees. This can vary on the variety so be sure to check that carefully.
You started off with old green tea. Green tea, when properly packaged, has a shelf life of about 6 months. Once opened you have about 2 months to use it. That's for properly packaged (vacuum packed or nitrogen packaged) tea. If your green tea wasn't packaged properly and is exposed to any amount of air, it probably was never good to begin with.
Your green tea was from a later harvest. It's no big secret - the best green tea comes from the first harvest in late April, early May. First harvest green tea is available throughout the year however if it's properly stored under cold storage and released as needed.
You brewed it too long. This depends on the variety, but generally speaking, no more than 2 minutes. Many sencha’s will taste best at even one minute or less.
You used too much tea. This is where you have more room for adjustment. Again, it depends on the variety but for normal sencha about one teaspoon to 8-10 ounces (230-300 ml) of water. Again, it will vary from tea to tea.
You didn't use enough tea. For gyokuro, you won't get good results unless you use double the amount used for sencha.
You didn't use good water. You need good water. Bottled mineral water usually makes good green tea, city tap water seldom does.
You tried to use a tea ball or paper filter. Green tea is compact. Once you brew it really expands and needs plenty of space to open up.
You tried to use a 2 liter English Teapot. If you really know what you are doing it is possible to use a Western teapot to brew green tea. You would be way better off using one designed for green tea, however.
You started of with low quality tea. Even in Japan the quality levels of green tea vary considerably. Just because it's from Japan doesn't necessarily mean it's good.