This brewing technique involves brewing the tea in hot water, then cooling it quickly by pouring the hot tea into a glass filled with pieces of ice.
Particularly in the case of Sencha, you can enjoy the refreshing and astringent taste that Sencha is well-known for, because this hot brewing technique extracts Catechin and Caffeine that are not extracted by brewing with ice or cold water. This way is also suitable when you wish to enjoy the healthful benefits of Catechin and Caffeine, such as when you would like to concentrate or have energy. This way is suitable for Gyokuro and Sencha Konacha.

• Place 7 to 8g (1.5 tablespoons) of Gyokuro or Sencha Konacha tea leaves into the Kyusu (teapot).
• Pour 200ml (7.04fl oz) of 176F (80C) temperature of water into the Kyusu.
• Wait for 2 to 3 minutes. You'll want to brew the tea quite strongly because later the thawed ice will weaken the flavor.
• Pour tea from the Kyusu into each glass filled with pieces of ice to cool the tea quickly. Pour alternately little by little, so that the quantity and taste of the tea is equal in each glass.

This brewing process is easy to do and creates tea which is easy to store and preserves well. You can enjoy the smooth and mellow taste of both Gyokuro and Sencha without any bitter notes because Caffeine is not extracted in cold water.
This way is suitable for Gyokuro and Sencha Konacha.

• Place 7 to 10g (1.5 to 2 tablespoons) of Gyokuro or Sencha Konacha tea leaves into the teapot (or large size Kyusu).
• Pour 500 to 1000ml (17.6 to 35.2fl oz) of cool water into the teapot (or large size Kyusu) and store in the refrigerator for 3 to 6 hours.
• In order to equalize the taste of the tea, shake the Kyusu horizontally before pouring the tea into each glass.

When you brew tea in this way, it is convenient to use a teapot for iced tea like the picture that is designed to brew iced tea. And Dobin and Large Kyusu are also convenient for iced tea brewed by cool water. They are available at Hibiki-an's Teapots / Cups category.
(You can visit the Iced Tea Pot page by clicking here; Iced Teapot, Teapot CLEAR - Filter Top, MIZUTAMA Dobin, TOBIKANNA Large Kyusu, T - Free)