When I saw this teapot on the internet, I was simply enchanted. I was thinking of the right adjectives to properly describe this teapot - burnt, soiled, rusted or even buried. I am sure you may have a different description of this teapot.
This is a Japanese bizen teapot. This kind of pottery is characterized by the unique use of wood fired kilns where the ashes are 'allowed' to fly within the kiln when such pottery are being fired. The ashes, in turn might scorch, burn or even get embedded on the surface of these pottery, thus creating the unique look of bizen pottery.
This is my second bizen ware purchase. My earlier purchase (see last pix) was a bizen tea brewing set (link). You will notice that the bizen tea set had pronounced scorched marks but there were less ash being incorporated on the surface of the tea set during the firing process.
My bizen teapot can hold about 160ml of tea. It is similar in size to my purion teapot and a couple of my Chinese clay teapots. It would be interesting to see how this teapot compares, in terms of brewing, with my other teapots. Stay tuned for the royal teapot rumble coming this summer !