Mumyoi is the red color soil which is produced in the gold mine of Sado, small island of Japan.
Originally Mumyoi is used for Chinese Medicine for curing food poison or stopping blood.
People in Sado started to produce tea pot using Mumyoi about 100years ago as the products become stronger and tea taste will improve.
Ryuso Kairagi is only made by Iwasaki Masao.
The unique things of his artwork is not only appearance, using his tea ware, flavor and taste of tea become much more stronger.
Especially fermented tea like iron Buddha Tea or Black tea.