Continuing the previous posting…
5 – Is the interior sloping inwards towards the bottom?
Avoid a chawan whose interior walls meet the bottom at a precise 90-degree angle. You don’t want there to be any corners of the chawan which cannot be reached by the whisk, otherwise the tea will contain undissolved clots of matcha. That’s not much fun for the person drinking it! Even a chawan that shows little evidence of curves on the outside will have an interior that slopes towards the bottom, if it is made with its true function in mind.
The best way to judge a chawan’s appropriateness for matcha preparation, of course, is to whisk some matcha in it. Obviously, you can’t do that when looking online! However, if you’re considering a bowl in person (particularly if it’s western-made), you have a little more leeway.
One member of the Yahoo group wakeiseijaku describes her habit of carrying a whisk (chasen) in her purse – I assume it’s stored inside a whisk case! – and evaluating any candidate bowls by “air-whisking” with it. This is preferable to handing over a wodge of money, getting the bowl home, and discovering that the diameter is just a little too narrow to manipulate the whisk, or the proportions just a little too confined…
Questions 4 and 5 belong to a larger, more general, and arguably vaguer consideration:
6 – Is the chawan well proportioned?
Traditional Japanese potters have settled on a range of chawan shapes for a reason: they work well. A well-shaped chawan is a pleasure to prepare tea in and to drink tea from. This doesn’t mean that you shouldn’t buy a bowl of an unusual shape, but you are always safe in selecting one of the traditional styles (e.g. the V-shaped Ido style, which was modelled on the Korean rice bowl of Rikyu’s time).
7 – Is the bowl a reasonable weight?
Bowls in Chadou shouldn’t be too heavy. I can’t even give you an ideal weight here – it’s something you “know” when handling a bowl. So this is a bit of a question mark. In general, Raku ware is lighter in weight than other pottery such as Kyoyaki, Bizen, Shigaraki, Hagi, Mino, and so forth. If the bowl strikes you as leaden when you weigh it in your hand, it’s too heavy.
Having said the above… many if not most of these concerns may not be relevant to you if you are a non-practitioner of tea ceremony.
And having given a sort of chapter-and-verse response, I’d like to add this:
I really feel that one of the best things we can do is to take chances with pottery, and to learn what works (or doesn’t) by working with it. By doing this, you’ll know experientially what to look for and what to avoid. Looked at this way, there are no “mistakes”, just learning opportunities.
If a bowl’s price is not high, and you really love the look of it, why not buy it and see whether it meets your needs? If you find you don’t care for it as a matcha bowl, you can always use it for other purposes (to hold sweets, nuts, etc.) – or simply enjoy displaying it.
Also, I’m a big believer in buying pottery that speaks to your spirit. If a piece strongly appeals to you, and you would feel badly if you let the opportunity pass, I think you should yield to passion and buy it.
In which case I’m saying yes, yes, yes!
Jaanus webpage on chawan, with cross-section of the chawan showing its parts and their Japanese names
Some great reference articles on e-yakimono.net:
A Guide to Styles
Keshiki – Ceramic Landscapes
Kodai – What’s the Fuss about the Foot
The Box – Don’t Throw It Away
Caring for Your Pottery
Tips on Displaying Your Pottery
Thoughts of a chawan collector