Select the Tea

• You can use a cast-iron teapot for any tea leaves you prefer -- black tea, oolong, rooibos or herbal. But given the Japanese heritage of the tetsubin, most folks brew either green tea, particularly sencha, the traditional green tea bought from China to Japan, or the lighter oolongs. A little goes a long way -- measure about 1 teaspoon for every 8 ounces of hot water, which you can do while you bring the water to just under a boil.

Prep the Water and Cast-Iron Pot

• For sencha and other green teas, you want to bring the water to 175 to 185 degrees F, which you can measure with a cooking thermometer, or eventually estimate by how vigorously your kettle is vibrating before it actually whistles. The water is best before it reaches the boiling point. But if you need to, you can let a boiled kettle rest and cool slightly; this water, though, will be slightly less oxygenated and thus a bit less optimal. Pour hot water in the teapot and swirl it around; then pour it out. This warms the teapot, which can actually keep your brewed tea itself warm for an hour. Add the leaves to the built-in strainer basket or the pot itself.

Time the Brewing

• Green tea is one of the fastest teas to brew -- you only need 90 to 120 seconds, depending on your taste. Avoiding letting the leaves sit in the hot water, which creates an undesirable stewed flavor.

Decant the Tea

• You can remove the strainer basket with tongs and enjoy your perfect tea. With any luck, your tetsubin came with matching, cast-iron cups, which enhance the tasting experience. If you don’t have a built-in strainer basket, pour the tea through a cup-style strainer or into a separate warmed vessel. You can brew green tea leaves up to five additional times, if they are not allowed to sit in hot water between infusions.