Traditionally the tetsubin design was made for brewing sencha, a quintessential Japanese green tea produced throughout the year.
Sencha is the most popular tea in Japan. Much different than matcha, it is a leaf tea, plucked and processed throughout the harvest seasons. The first and second flush sencha are considered the best, sweeter in taste and stronger in flavor than each subsequent flush.
Unlike China or India, the specific tea estate or region is not named in the selling of sencha. Almost always, sencha tea is blended with the signature touch of each artisan, creating a signature brand for the tea company or shop. No matter the grade, all sencha is high in vitamin C.
Most Japanese tea is not made for export. It’s probably safe to say that what is exported is probably not their very best tea. Although I have had excellent sencha from Adagio Tea, I recommend their masters collection. It’s a good place to start.