Clay kyusu has a long history in Japan for making green tea in. Indeed, when Yixing teapot began to take its place as the de facto teaware for connoisseurs, the overwhelming majority of tea in the market was green. Poems and literature have presented them as pairs since the 17th century.
Personally, I think many green teas don’t show their true face unless they are prepared with a properly seasoned Yixing pot. However, for people who prefer sharper tastes the porcelain is a great category of infusion wares.
For white teas, I mean true white teas, I prefer porcelain over Yixing, as they are soft as they are, any further rounding of the body seems a bit too much. I’d rather shorten the infusion by using more leaves and higher temp for some briskness. I drink white tea by the gulp, unlike I would fine greens.
In choosing the proper Yixing clay for the tea, I’d consider the taste profile of that particular tea rather then what category it belongs to. I’d also consider how I would drink the tea: small cup, medium cup, normal cup, or large cup? This also determine the decantation speed, the pot size, and thus the needed thickness and density and in turn affects the body and texture.
If we don’t regard the above factors and confine ourselves to smaller pots and normal spout speed and shorter infusion time, then for softer teas you use a higher density clay and sharper teas a lower one.
Another factor that most people overlook when judging a pot is the need for proper seasoning of most genuine pots. Thicker clays need more seasoning than thinner one. Clays blended in more silica need less than those purer ones. Softer teas are affected more obviously when prepared with an under-seasoned pot than sharper ones.
The way you pour water into the teapot and the shape/size of the teapot affect the infusion effects and seldom is the case of stuck green tea not having enough room for spreading, when you know what to do.
I agree with Hokusai that glass really is not an ideal infusion ware, unless it is really thick.
