I recently purchased my first Kyusu, and there is a glaze on the outside, but the inside is unglazed. I asked a lot of questions to the very helpful owner of artistic nippon. He informed me that unlike Chinese clay, glaze on the outside of Japanese clay should not affect the tea.
I own a Yixing pot as well and, from my understanding, it is bad for any type of glaze to be on the pot because this will limit the porousness of the pot. This is also the same line of reasoning I use when I age my puerh in a Yixing pot so that air can come and go through the pores. It makes sense to me that there shouldn't be a glaze on Yixing clay in order to promote the greatest amount of air flow. possible
Conversely, I don't understand why glaze is acceptable on Tokoname. I was told that the tea can still season the inside of the unglazed pot which makes sense to me, but doesn't an external glaze eliminate most of the porousness? If there is a glaze on the outside, then air can not flow in and out of the pot. Is porousness just a non-factor when brewing Senchas?
Why is glaze acceptable on Tokoname Clay, but not on Yixing/Nixing/Jianshui?
could you share a pic of the glazed kyusu?
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King_of_Peony
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Unless underfired (which is not uncommon in older pots), most yixing don't have pores that go through the walls: when they do one sees bleeding of tea gunk through it when brewing. I don't believe air passes through the clay in any considerable amount. So outside glaze wouldn't change much. In fact, there are some old pots (and new replicas) that are fully enameled on the outside, and there are also neiziwaihong pots coated in fine clay, which is sort of a glaze. I think main reason why glazing isn't big with yixing, is that the beauty of zisha, and what makes it really unique, is the fine texture of the clay. And the way it changes and shines when hot water is poured in it. This would be lost when glazed.King_of_Peony wrote: ↑Sat Jan 01, 2022 7:35 pmI own a Yixing pot as well and, from my understanding, it is bad for any type of glaze to be on the pot because this will limit the porousness of the pot. This is also the same line of reasoning I use when I age my puerh in a Yixing pot so that air can come and go through the pores. It makes sense to me that there shouldn't be a glaze on Yixing clay in order to promote the greatest amount of air flow. possible
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While I can’t speak extensively about the Chinese tea ware end of things, I do know that some types Yixing are really famed for their dual porosity (developed primarily during mud training portion of clay processing). I’m personally skeptical about the effect this outer layer of porosity has on the brewing tea inside, but it certainly helps develop really beautiful patinas on the outside of pots. So I’d imagine if you’re going through the trouble of processing clay like this, you’d be discouraged from covering up that potential with a glaze.
Japanese clay and tea ware is a bit different. Tokoname clay, like your reduction-fired shudei pot, is much less porous than Yixing and other types of Chinese clay. Additionally, it’s fired at a higher temperature, which usually makes the clay behave closer to glass or porcelain. This is why they’re generally preferred for gentle teas like green, perhaps controversially, they simply don’t swing the flavor too much in any direction. So glazing these types of high-fired, not particularly porous clays doesn’t change much. Not to get too into the weeds, but there are other types of Japanese clay that will be glazed for other reasons; some Shigaraki clays for example can be so porous, that if you didn’t glaze, liquid would weep through the pot.
Lastly, and I think this holds more explanatory power than how different things affect tea, is that there are just cultural artistic differences between China and Japan. You see much more porcelain and celadon from China than you do from Japan. Conversely, thicker glazed works like what’s found in Mino-yaki are more typical of Japan. This isn’t to say that they’re exclusive to one another, but I think this influences the tastes and trends of the makers from each area. At least that’s my opinion.
Japanese clay and tea ware is a bit different. Tokoname clay, like your reduction-fired shudei pot, is much less porous than Yixing and other types of Chinese clay. Additionally, it’s fired at a higher temperature, which usually makes the clay behave closer to glass or porcelain. This is why they’re generally preferred for gentle teas like green, perhaps controversially, they simply don’t swing the flavor too much in any direction. So glazing these types of high-fired, not particularly porous clays doesn’t change much. Not to get too into the weeds, but there are other types of Japanese clay that will be glazed for other reasons; some Shigaraki clays for example can be so porous, that if you didn’t glaze, liquid would weep through the pot.
Lastly, and I think this holds more explanatory power than how different things affect tea, is that there are just cultural artistic differences between China and Japan. You see much more porcelain and celadon from China than you do from Japan. Conversely, thicker glazed works like what’s found in Mino-yaki are more typical of Japan. This isn’t to say that they’re exclusive to one another, but I think this influences the tastes and trends of the makers from each area. At least that’s my opinion.
As mentioned there is glazed Yixing, though personally I don't tend to like the colors used on older Yixing. You'll also find fencai/similar decoration on some older Chaozhou pots, even some Japanese pots. I've never seen painted Nixing new or old, or Jianshui - what people tend to prize in Nixing is the variety of colors and fades created by the kiln itself, so painting over them would be pointless to most. Some more modern elaborate Nixing which I'm not such a big fan of also has really detailed carving, and the price is driven up due to the skill of the carver since the price of more plain pots isn't particularly high in relation to Yixing. Same goes for Jianshui, either with complex carving and/or colored inlay - though from what I've understood if you develop an eye and know what you are looking for you can also spot how often carving or adding additional clay to the outside in flowers or other little shapes is also used to cover up mistakes/sloppy craftsmanship or firing problems on the original construction of the pot.
There are some wonderful answers above that go into great detail.
I’ll contribute a kind of TL;DR comment to the subject:
1) Porousness is a poor indicator of a given clay’s effect on tea.
2) Double-porousness is a myth except in under-fired pots (& HQSN?) and is unlikely to do anything good* for tea. It probably started as a kind of marketing statement based upon a poor understanding of teapots and tea.
3) Tokoname clay is often as much or more porous than Yixing clays.
4) Cultural aesthetic differences are responsible for what materials are and are not glazed.
* Someone is certain to like clays like this for tea. Fair enough but there are people who like Tabasco sauce in their black coffee. These people are outliers.
I’ll contribute a kind of TL;DR comment to the subject:
1) Porousness is a poor indicator of a given clay’s effect on tea.
2) Double-porousness is a myth except in under-fired pots (& HQSN?) and is unlikely to do anything good* for tea. It probably started as a kind of marketing statement based upon a poor understanding of teapots and tea.
3) Tokoname clay is often as much or more porous than Yixing clays.
4) Cultural aesthetic differences are responsible for what materials are and are not glazed.
* Someone is certain to like clays like this for tea. Fair enough but there are people who like Tabasco sauce in their black coffee. These people are outliers.