Edokiriko – Stripe Sake Glass Teapot The deep black color is

The deep black color is achieved using a traditional “Tetsu-yū” (iron glaze) technique

It is also said that the essential oil components of fir have a deodorizing effect

and again when you use it

but this one uses persimmon tannin paper with blended color powders for a more vibrant hue

Edokiriko – Stripe Sake Glass Teapot The deep black color isWhen a tree is cut perpendicular to its growth rings, the resulting surface displays a straight grain called "masame" in Japanese. Masame, a premium material, can only be obtained from the center of a log. This glass imitates that straight grain pattern, incorporating it into its design as evenly spaced stripes.