I am making the distinction, because this last trip to Korea and the tea bowl festival really accented the differences between the preferred shape of a tea bowl between cultures.
The one type of bowl here that probably illustrates the point best, but of which I don’t have a good example, are the Ido chawan. We make these forms in Karatsu, but don’t refer to them as Ido Chawan. Rather, we call them Karatsu Ido, or Ido Gata Chawan. The original Ido Chawan are from Korea, and contrary to the idea that the ideal shape is like Kizaemon (below), Ido come in many shapes and sizes. I’ve even seen on Ido bowl with a warikodai (foot carved into sections).
Anyway, if you look carefully at Ido forms, two things are often noticed: One, the lip is quite sharp on the inside edge, even though the outside of the edge is rounded, and two, the interior of the bowl is not rounded but rather pointed. These characteristics seem unrelated or even impractical for tea, after all, who wants a lip that is less durable, wouldn’t a round lip be more practical? Also, a cone shaped pointed interior is not suitable for whisking tea, is it? There is no room for the whisk to move, after all.
So why did tea masters choose these bowls as paragons of ‘teabowlness’? The answer is simple. They weren’t used for whisked tea. Most tea practice revolves around usucha, or whisked thin tea, but the tea that holds the highest position in tea ceremony as an indispensible part of Chaji, the full tea ceremony, is koicha, or thick tea. Thick tea is not whisked, it is kneaded and folded slowly into a thick paste with the whisk, and the coned interior of the bowl allows for this to happen much better than a flat or rounded interior. Then when drinking this thick paste, it is much better to have a sharp interior lip in order have a clean separation from the bowl when drinking. Koicha is usually a shared bowl, and will be shared by two or more people. After drinking, you must wipe the lip and pass it along to the next person. The sharper interior lip makes both drinking and wiping an easier less messy experience. So, these two characteristics end up being optimal for tea, in the proper context of Japanese koicha.
Even more interestingly, these two characteristics were not intentionally designed by the makers with koicha in mind. They are the direct result of the clay, process, and tools used to make the bowls, which were likely made quickly in large numbers.
In Karatsu, we use cows tongue ribs to shape the clay, because it is large particle material and not very plastic. In some cases, such as porcelain stone and sandstone, it is not even clay at all. The cows tongue allows shaping by compressing the clay body, rather than stretching, like a standard rib would do. I always thought that cows tongue ribs came from Korea, but I have never seen one there during my visits. There is, however, a tool that looks a little like a mini tugboat that functions much the same way as a cows tongue. When making bowls quickly with as little wasted movement as possible, the interior of the bowl naturally becomes conical rather than rounded, and pressing the lip between finger and cows tongue naturally produces the characteristic Ido lip shape, while preventing splitting of the lip by compressing the un-plastic clay body, and also eliminates the need to use a chamois on the lip to compress or clean up.
So, I seem to have gotten off on a bit of a tangent here, but back to the main goal of simply leaving you with some images of tea bowls: