Japanese Clays and Techniques

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pedant
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Discuss yakimono, Japanese clays, and ceramic techniques here!
Feel free to contribute images, definitions, text, or corrections; we'll periodically use them to update this post :mrgreen:


Clays

Note that many of these end in dei [泥], which means mud or clay. This is the same character for in Chinese.

Shudei (Red clay) [朱泥 or しゅでい]

Traditional earth color. This clay is the basis of Tokoname kyusu. Modern shudei often has iron oxide added to give a bright red color, while natural/traditional shudei (hon shudei [本朱泥]) has more of an orange tone.

wanted: comparison image of red doped shudei vs orange honshudei

Although the kanji for shu dei is the same as the characters for zhu ni in Chinese, the clays are not the same.

Shidei (Purple clay) [紫泥 or しでい]

In some works, purple color is achieved through the addition of manganese dioxide (MnO2).
In others, purple color is produced via reduction firing. For example, purple Banko-yaki is made from a clay that is yellow before firing.

In Chinese, the characters are the same as for zi ni, though the clays are different.

wanted: shidei image

Udei (Black clay) [烏泥 or うでい]

wanted: udei info and image

Hakudei (White clay) [白泥 or はくでい]

One of the traditional Tokoname clays.

Jozan II: Shudei & Hakudei clays
Jozan II: Shudei & Hakudei clays
Jozan II - Shudei vs Hakudei.jpg (213.93 KiB) Viewed 11023 times
Hakudei is shown on the right.



Techniques

Yakishime (Fired) [焼締め or やきしめ]

Refers to ceramics fired without glaze.

Rihi (Pear skin) [梨皮 or りひ]

A technique where grog (sand, porcelain chips, or similar) is kneaded into the clay to give a gritty texture reminiscent of pear skin.

Jozan IV: Rihi (pear skin) detail [Victoria]
Jozan IV: Rihi (pear skin) detail [Victoria]
Jozan-IV-Shudei-Rihi-(Victoria).jpg (52.62 KiB) Viewed 10962 times

Mogake (Seaweed) [藻掛け or 藻がけ]

Sometimes affixed with string, seaweed is draped over the piece. Minerals from the seaweed melt and form a glaze when fired, and a pale red pattern is left behind.

Mogake before firing (Artistic Nippon)
Mogake before firing (Artistic Nippon)
AN-mogake.jpg (16.89 KiB) Viewed 10847 times
Credit: Artistic Nippon

Mogake before firing (tokoname.or.jp)
Mogake before firing (tokoname.or.jp)
mogake Fugetsu tokoname.or.jp.jpg (62.2 KiB) Viewed 10451 times
Credit: Fugetsu / tokoname.or.jp

Hokujo: Mogake detail
Hokujo: Mogake detail
Hokujo-Mogake-Shiboridashi.jpg (123.28 KiB) Viewed 10926 times

Oxidation & Reduction Firing [酸化/還元 焼成]

Many clays are rich in transition metals which change colors depending on their oxidation state. For example, Iron(III) compounds are often reddish, while Iron(II) compounds are often brown-black-purple.

Here is a nice image from Hojo Tea showing how two different clays look before firing, after reduction firing, and after oxidation firing:

Oxidation vs Reduction Firing (Hojo Tea)
Oxidation vs Reduction Firing (Hojo Tea)
hojo-clay-firing-comparison.jpg (224.39 KiB) Viewed 10839 times

Because clay is only so permeable, the color change is usually limited to the surface. This effect is exploited in this reduction-fired piece:

Gyokudo: Reduction-fired engraving detail
Gyokudo: Reduction-fired engraving detail
Gyokudo-engraving-detail.jpg (76.45 KiB) Viewed 10837 times
(source)

The surface has been scraped away to reveal red clay beneath.

See also: Demystifying the Reduction Firing Process

Yohen (Kiln transformation) [窯変 or ようへん]

A technique where often heterogeneous conditions in the kiln result in a visual effect or transformation. It can be achieved in various ways but is usually dependent on special positioning in the kiln or partially covering the workpiece. For example, in a wood fired kiln, a more exposed part of a piece may "transform" if wood ash is allowed to fall on it and form a glaze.

wanted: some kind of mayake transformation image

A common type of yohen arises from a carbon monoxide (CO) gradient in the kiln's atmosphere, either from a draft or from partially covering the piece. Many clays are rich in transition metals which change colors depending on their oxidation state. For example, Iron(III) compounds are often reddish, while Iron(II) compounds are often brown-black-purple. Areas that are exposed to a more reducing atmosphere turn darker in color:

MURATA Yoshiki: Yohen kyusu
MURATA Yoshiki: Yohen kyusu
yoshiki-yohen.jpg (58.46 KiB) Viewed 10841 times
(original post)

Shizenyu (Natural ash glaze) [自然釉]
or Kaiyū (ash glaze) [灰釉]

Usually fired at >1100°C in a wood-fired kiln, ash from the fire is deposited onto the clay and melts to form a natural glaze. The effects are mostly random but are influenced by airflow and position in the kiln.

Hidasuki (Scarlet/fire cord) [緋襷 or ひだすき]

Bizen technique where ceramics are wrapped with rice straw before firing. A red pattern is left behind.

Hidasuki before firing (tokoname.or.jp)
Hidasuki before firing (tokoname.or.jp)
hidasuki Fugetsu tokoname.or.jp.jpg (49.88 KiB) Viewed 10451 times
Credit: Fugetsu / tokoname.or.jp


wanted: image after firing


Nanban (Foreign style, lit. southern barbarian) [南蛮 or なんばん]

Nanban literally means "southern barbarians" and originally refers to the people of South/Southeast China. It seems to also refer to trade with Europeans in the 16th and 17th centuries, so perhaps more generally, it refers to foreign influence.

Ceramics imported from South China, Vietnam, the Philippines, etc. during this time were referred to as nanban-yaki. Nonuniform in appearance, these ceramics were prized by Japanese tea masters of the era.

Over time, the definition of Nanban has become unclear, but generally, it means inspired by foreign pottery.
In Tokoname, Nanban refers to yakimono with a coarse surface.


Further reading:
https://ja.wikipedia.org/wiki/南蛮焼
https://en.wikipedia.org/wiki/Nanban_art
https://en.wikipedia.org/wiki/Nanban_trade

Hokujo: Nanban detail
Hokujo: Nanban detail
Hokujo-Nanban-Kyusu.jpg (86.61 KiB) Viewed 10937 times
(original post)



Resources:



To do:

mayake
Glazed: Shino glaze, Oribe glaze
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pedant
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Fri Jan 22, 2021 7:26 pm

reserved for later use
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pedant
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Fri Jan 22, 2021 7:26 pm

Idemitsu Museum: Jozan III p. 54
Idemitsu Museum: Jozan III p. 54
jozan3-scan-p54.jpg (214.41 KiB) Viewed 10828 times

from Yamada Jōzan III: "Living National Treasure", His Spirit and Ceramics, Idemitsu Museum of Arts (2012)

i thought this was kind of cool.

here's a poor translation:

白泥/はくでい
常滑急須の伝統の一つ。三代常山作品では珍しい。
Hakudei (White clay)
One of the traditions of Tokoname Kyusu. Rarely used by Jozan III.

梨皮/りひ
各色土に、砂磯を練り込んだ土。
Rihi (Pear skin)
Soil kneaded with sand shore in each colored soil.

烏泥/うでい
紫泥に更にマンガンを加えた暗褐色の土色。
Udei (Black clay, lit. crow clay)
Dark brown soil color with manganese added to purple mud.

紫泥/しでい
朱泥に二酸化マンガンを加えた暗紫色の土色。
Shidei (Purple clay)
Dark purple earth color with manganese dioxide added to vermilion.

朱泥/しゅでい
常滑急須の基本となる、伝統の土色。
Shudei (Vermilion clay)
The traditional earth color that is the basis of Tokoname Kyusu.

--

自然釉
三代常山の自然和は登窯で数回焼き重ねて作られている。
Natural glaze
The natural sum of Jozan III is made by baking several times in a kiln.

南蛮/なんばん
やや粗い土を低温で焼き、赤褐色と柔らかい質感を得る。
Nanban
Bake slightly coarse soil at low temperature to obtain a reddish brown and soft texture.

緋襷/ひだすき
窯変の一種で、備前焼の技法を取り入れた技法。
Hidasuki (Scarlet)
A type of kiln change that incorporates the technique of Bizen ware.

窯変/ようへん
籾殻で嫌し焼きをして、還元炎焼成による色の変化を作る。
Yohen (Kiln change)
Dislike baking with rice husks to make a color change by firing with a reducing flame.

藻掛け/藻がけ
海瀬を使い、その塩分で淡紅色を得る。常滑急須の伝統。
Mogake (Algae hanging)
Use Kaise and get a pink color with the salt content. Tokoname Kyusu tradition.
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LeoFox
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Fri Jan 22, 2021 9:40 pm

Wonderful post!
I wonder if you have seen this website that contains a lot of information:

https://chano-yu.com/types-of-japanese- ... porcelain/

https://chano-yu.com/famous-japanese-potters-and-marks/
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Victoria
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Sat Jan 23, 2021 2:26 pm

Clays by Regions and Six Ancient Kilns (will be updated to include specific clays and additional regions)

Clays by Regions
Aichi;
  • Tokoname-yaki, Tokoname, Aichi Perfecture
  • Seto-ware, Seto, Aichi Perfecture
Mie;
  • Iga-yaki, Mie Perfecture
  • Banko-yaki, Yokkaichi, Mie Prefecture
Additional (in progress);
  • Shigaraki, Shiga, Shiga Prefecture (adjacent to Mie)
  • Kyo-yaki & Kiyomizu-yaki, Kyoto, Kyoto Perfecture
  • Arita-ware (Imari-ware), Arita, Saga Prefecture
  • Bizen-yaki, Bizen province, Okayama Prefecture
  • Kutani, Kaga, Ishikawa Perfecture
&

Six Ancient Kilns:
__ Tokoname and Seto (both in Aichi Prefecture)
__ Echizen (Fukui Prefecture)
__ Tamba (Hyōgo Prefecture)
__ Bizen (Okayama Prefecture)
__ Shigaraki (Shiga Prefecture)
student t
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Sat Jan 30, 2021 2:43 am

This is very useful; thank you for starting it.

Rihi clays have always been a bit of a mystery for me.

Apart from the mentioned textural change to be more gritty like pear skin, as in the nice Emu pot picture, I also often see that the added element provides a striking color contrast --visible white or yellow dots.

So what has been a mystery for me is the substantial price premium often associated with rihi teapots. Is this just a spurious association (for instance, when making what will be a one-off high-quality teapot, the potter, among other things, chooses to use rihi clay)? Or is it more expensive/difficult to make a rihi teapot in itself? I think it is probably more the first explanation: rihi as a sort of quality signalling device. But it could be also that by mixing harder bits into the clay the firing breakage rate increases or something like that.
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Baisao
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Sat Jan 30, 2021 3:22 am

@student t, I have a pear skin kyusu by Emu. It was purchased second hand and for less than his regular shudei pots. The pear skin effect is stunning and photos can not do justice to it. In the case of Emu, the clay is obviously less wet than his regular shudei and shows fissures in places where the clay tore in forming the kyusu. Adding grog in the form of small bits of white stone should help with the firing, or that is my understanding. Amateur potters frequently add grog to make difficult clays more successful. I am surmising that the added bits in his pear skin kyusu also help with this very dry clay.

Like zhuni, it changes with light. Sometimes more red and other times less vividly red. I increased the warmth on the first photo to better match what it looks like in sunlight.
Attachments
Emu Yamada - pear skin
Emu Yamada - pear skin
3707C5A7-F19D-45AC-ADA9-2773CBEFE511.jpeg (318.14 KiB) Viewed 10584 times
Emu Yamada - pear skin 2
Emu Yamada - pear skin 2
3E998B07-639A-45D6-AA6E-EF80068A54E9.jpeg (726.64 KiB) Viewed 10584 times
Emu Yamada - pear skin 1
Emu Yamada - pear skin 1
FF9A1598-145B-4954-8E16-9EE054400716.jpeg (521.29 KiB) Viewed 10584 times
student t
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Sat Jan 30, 2021 4:11 am

Many thanks, Baisao--I didn't know that.

Stunning pot!!
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LeoFox
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Wed Feb 17, 2021 8:36 am

Nice resource for chops and potter history
https://japanese-ceramics.com/
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Victoria
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Wed Feb 17, 2021 3:05 pm

LeoFox wrote:
Wed Feb 17, 2021 8:36 am
Nice resource for chops and potter history
https://japanese-ceramics.com/
Great find, thanks for sharing!
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Bok
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Thu Feb 18, 2021 12:05 am

Victoria wrote:
Wed Feb 17, 2021 3:05 pm
LeoFox wrote:
Wed Feb 17, 2021 8:36 am
Nice resource for chops and potter history
https://japanese-ceramics.com/
Great find, thanks for sharing!
+1 Excellent indeed! Thanks @LeoFox
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Yoroko
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Tue Mar 02, 2021 9:04 am

@pedant
Here we go with a link concerning a Hon Shudei teapot.
https://hojotea.com/item_e/teapot02e.htm
Please scroll down to the end of the article. There you will find 2 pictures of real Hon Shudei teapots. The Hon Shudei is more orange than the Shudei mixed with iron particles. I've some more pictures of real Hon Shudei Kyusus: they are even more orange; but I can't find them right now. As far as I know more than 99% of all Tokoname Kyusus are made of mixed clays and most of the time with added iron; nice looking but the performance is in my opinion questionable.
faj
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Tue Mar 02, 2021 1:14 pm

Yoroko wrote:
Tue Mar 02, 2021 9:04 am
pedant
Here we go with a link concerning a Hon Shudei teapot.
https://hojotea.com/item_e/teapot02e.htm
I happened to be making sencha with this new friend when I read your message and took a quick shot. I do not know if it is "hon shudei", but it is from the same potter. Unfortunately, I was not able to capture the color right (you can probably notice the colors in my picture are too warm). In real life, it is less red, and less dark than the way my monitor renders the image. It is a very soft (low saturation, if you will) orange tending toward light brown.

Weirdly enough, Hojo has chosen pictures that make Gisui's pots look way more red than what I have seen from vendor pictures, even if the text highlights the "not red" aspect.

gisui.jpg
gisui.jpg (69.79 KiB) Viewed 9907 times

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Baisao
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Tue Mar 02, 2021 3:50 pm

Yoroko wrote:
Tue Mar 02, 2021 9:04 am
pedant
Here we go with a link concerning a Hon Shudei teapot.
https://hojotea.com/item_e/teapot02e.htm
Please scroll down to the end of the article. There you will find 2 pictures of real Hon Shudei teapots. The Hon Shudei is more orange than the Shudei mixed with iron particles. I've some more pictures of real Hon Shudei Kyusus: they are even more orange; but I can't find them right now. As far as I know more than 99% of all Tokoname Kyusus are made of mixed clays and most of the time with added iron; nice looking but the performance is in my opinion questionable.
If you look around the site you will find multiple photos of hon shudei. As for clay with added iron having “questionable” performance, I find that comment questionable. The performance differences are more imagined than factual when it comes to shudei vs hon shudei by the Yamadas. Perhaps it is different with other potters.
Last edited by Victoria on Tue Mar 02, 2021 4:21 pm, edited 1 time in total.
Reason: Mod edit: removed duplicate quote
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Bok
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Tue Mar 02, 2021 9:25 pm

Second that, I highly doubt anyone could notice but a very subtle difference of any at all. Sometimes I wonder about all these super tasters...
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