Clay & glaze

Clay colour · 泥色 · Yixing

vermilion clay · unglazed

The warm red-brown of an unglazed Chinese pot. With shidei it is one of the two clays that most Chinese pots in Japan are made from, and the one people picture when they picture a Chinese bonsai pot at all.

Yixing is where the pots were gathered and sold, not where they were made. The kilns stood some twenty kilometres away around Shuzan and Teizan — today Dingshu, in Yixing county, Jiangsu. They were climbing kilns, half-buried tunnels running up a slope; the long ones linked dozens of chambers and approached a hundred metres, several times the scale of the largest kiln at Bizen. At their height, dozens of them were in smoke at once.

Age is the thing people most want from the colour, and it is the thing the colour gives least. Early imported shudei is scarce. Production for the Japanese market got going in earnest from the middle of the Meiji period, and it was not until the Shōwa era that shudei arrived in quantity. So a shudei pot is, on the balance of numbers, a twentieth-century pot — but no test separating one import period from the next is documented, and we do not invent one.

How to tell

• Red-brown, warm rather than bright. A pot in the vivid, almost scarlet register is more likely kōdei.
• Bright speckles across the surface make it nashiji-shudei 梨皮朱泥, “pear-skin”: refractory grit or grog in the body, the surface burnished before firing so the specks read as points of light.
• Fine and dense, or coarse and open. The finely levigated early clay is called neri-shudei; the coarser later body ara-shudei.
• A square one is a rarity. Square shudei pots are recorded as rare at any size.

Often confused with

Clay colour · 泥色 · Yixing

crimson clay · unglazed

Shudei’s close relative: redder, smoother to the touch, and very much scarcer — the surviving number is of the order of a few hundredth of shudei’s.

As a raw material it was known early and used in more ways than one. Unlike the shudei body it agrees with every other clay — this is attributed to its shrinkage behaving itself — so it was blended into other bodies to raise their plasticity, and used as a colourant. That is the origin of the caution below: a good deal of what looks like kōdei is kōdei laid over something else.

How to tell

• A stronger red than shudei, and a smoother skin. Those two together are the test; either alone is not enough.
• Smooth, or with a fine pear-skin. The difference comes from how far the clay was levigated; some pots have grog deliberately mixed in to get the speckle.
• No mark is the normal case — and, unusually, not a strike against the pot. Fine unmarked kōdei is characteristic, and the reason recorded for it is that the clay was scarce enough that first-rank workmen used it only on their best.
• When there is a mark, the ones associated with the better pots are 為善最楽, 蔣世龍 and 蕭紹明.

Often confused with

Clay colour · 泥色 · Yixing

peach-blossom clay · unglazed

A Japanese name for a colour the Chinese literature does not have. Very few survive, effectively all of them are unmarked, and effectively all of them are early imports.

The name is younger than the pots. Tōkadei appears as a category around the early Shōwa years, when bonsai in Japan was at a peak of activity and its vocabulary was being worked out in detail. Collectors had pots that were more luminous than udei but clearly not shidei or shudei, and that lacked the speckle udei almost always carries — so a new name was made for them. It is worth saying plainly: this is a Japanese act of discrimination, not a Chinese kiln term.

How to tell

• No pear-skin speckle. This is the working distinction from udei: a pot that would otherwise read as udei, but lacks the speckle, is what got this name in the first place.
• Neither shudei nor shidei nor udei — the colour is defined by what it is not, which is why judgements differ.
• Coarse grain tends to be the older work, and goes with simpler, straighter forms. The finer-grained pots are where the better work is.
• Unmarked. Essentially all of them are, so an absent mark tells you nothing either way.

Often confused with

Clay colour · 泥色 · Yixing

persimmon clay · unglazed

The colour of a ripe persimmon, sitting roughly between shudei and the white clay. Another name coined in Japan, and the scarcest of the clays here.

Two of the four carry a mark from the same hand — 蕭紹明 Shōmei, once as the name alone and once in the form 紹明倣古, “Shōmei, after the antique”. For so small a group that is a concentration worth noticing.

How to tell

• Orange-tan rather than red — past shudei on the way to the white clay.
• The tone has range. That is worth holding onto as a warning against a narrow idea of what kakidei looks like.
• Speckle in the body gets the pot called nashiji-kakidei 梨皮柿泥 — the same observation as pear-skin shudei, applied here.
• All four recorded pots are large, between 32 and 43.5 cm, and all are early imports. Not one small example is documented.

Often confused with

Clay colour · 泥色 · Yixing

purple zisha clay · unglazed

The dark purple-brown body known in the West as zisha, and the most numerous clay among the Chinese pots that survive in Japan. If you own one Chinese pot, this is most likely what it is made of.

The clay is easy to work and forgiving to form. The 2006 account records that the seam found in the Ming period had not run out and that shidei was still being made then. That single fact governs how a shidei pot should be read: being shidei tells you nothing about age. Four centuries of production stand behind it.

The import history has a shape worth carrying in your head, because it has a hole in it. Large quantities came from the Meiji and Taishō periods, and again from the 1923 earthquake through to the war. Then imports stopped altogether after the Sino-Japanese war, resumed for a spell between the 1960s and 80s, and opened up again from the Heisei period as private kilns multiplied. Each phase has its own name in Japanese. What is not documented is a way to tell them apart from the pot itself — so we name the phases and decline to assign one.

Marks deserve the same caution. Yixing is unusual among old Chinese kilns in that the names of individual potters were recorded at all, and a handful of those names appear on pots. But a mark is not proof: “Chen Mingyuan” turns up most often on later copies, and pots marked “Mansheng” were designed by Chen Mansheng and actually made by Yang Pengnian. A name on the base is a lead, not a verdict.

How to tell

• Purple-brown, darkening with age and watering. A well-used shidei pot is a good deal darker than a new one.
• Enormous variety of form and size. Yixing was not an official kiln like Jingdezhen but a crowd of private ones, so shape, design and scale run wider here than in any other single material — and quality under the same mark varies.
• Painted shidei is a category of its own. E-shidei 絵紫泥 is decorated in slip over a white ground, which is why its colours look soft beside the hard enamels of porcelain.
• Early pots are often unmarked. Absence of a mark is not absence of quality.

Often confused with

Clay colour · 泥色 · Yixing

crow-black clay · unglazed

The clay colour placed at the top of the Chinese range — and, in spite of the name, not black. U is the crow; the clay is silver-brown.

There is no Chinese term behind this name. China has no clay called udei; the word is the Japanese bonsai world’s own, in use by the Meiji period with its origin already lost. What it points at is a Yixing stoneware that came out of the late-Ming and early-Qing fashion for steeped tea, alongside the shudei and shidei teapots made for the same literati taste.

The body is a kind of zisha clay, but not a single earth: it is a blend of several zisha clays, its colour shifting with where the raw material came from, how it was compounded and how it was fired. And the clay at the centre of that blend ran out in the Qing. It is no longer produced. That is the one hard dating fact on this page — the bulk of udei is placed at early to mid Qing, two to two and a half centuries before 2006 — and it is the exact opposite of shidei’s situation.

How to tell

• Silver-brown, not black. Around that base it runs towards red in some pots, towards purple in others, and towards a strong grey-white in others again. It can be hard to separate from shidei.
• A fine pear-skin speckle is the norm, varying in size and density. Its absence is one reason a pot ends up called tōkadei instead.
• Usually unmarked. Where a mark exists it is rare enough to be an event — and it will not be in the middle of the base. The recorded examples are struck beside the foot, between the feet, or on the side wall above the foot.
• Small pots are scarce. Every udei pot in the main documented run is a large one; the small ones are treated separately and are far fewer than in shidei or shudei.

Often confused with

Clay colour · 泥色 · Yixing

black clay · unglazed

Black — and, alone among the clays here, not tied to a particular earth at all. Early kokudei is an accident of the kiln.

Yixing clay pots are fired in oxidation. But the old climbing kilns were long, and their heat was not even: a chamber could run too hot, or turn reducing. Where that happened, unburnt carbon was driven into the clay and the body came out black. That is kokudei — not a clay, a condition, and an uncommon one.

It was wanted rather than tolerated. Chinese ceramics grew up with archaic bronzes as its model, and a black pot reads as bronze. That is why the bronze motifs and the black body turn up together so often. Later the effect was reproduced deliberately, by adding manganese and iron to a shidei body and firing in reduction, and almost all modern kokudei is made that way.

How to tell

• Bronze-vessel decoration is the company it keeps. Two of the four recorded pots carry archaic bronze motifs, and that is not a coincidence — see below.
• Early kokudei is rare, because it depended on chance. Modern kokudei is not rare, because it is made on purpose.
• A black surface need not mean a black body. Nuri-kokudei 塗黒泥 is a slip.
• No small ones are documented — the four recorded pots run from 16.7 to 29.6 cm.

Often confused with

Clay colour · 泥色 · Yixing

white clay · unglazed

Scarcer than shidei or shudei, and — shape for shape and size for size — usually valued above them. It is also not white.

The clay comes from a different hill. Shudei and shidei were dug around Teizan and Dingshan; hakudei came from Daikozan, also called Nanzan, to the south — close enough to hand that it was in use from the beginning of unglazed production at Yixing.

Two quiet facts about quality belong together. The better the raw clay, the higher the proportion of fine pots — the good material went to the good hands. And even an ordinary-grade hakudei pot tends to carry an elegant shape. Put beside how few there are, that is why a hakudei pot generally stands above its shidei or shudei equivalent.

Now the practical one. A famous early hakudei pot has long been described as carved in relief. On that example the raised material differs from the body, which supports the conclusion that the decoration was trailed on as slip and then carved, rather than cut from the body. That is an observation about the one pot, not a test for every pot.

How to tell

• Never pure white. It runs from a yellowish white through pale brown to grey-white. The cause is simple: little iron, fired in oxidation, so the white comes out faintly yellow or brown.
• If it really is pure white, be suspicious. More likely a white slip — nuri-hakudei 塗白泥 — or a glaze.
• Some of it shades towards shidei. The group includes pots close in tone to the purple clay, depending on how fine the raw material was and how it was fired.
• Raised decoration may not be carved. See the observed example above.

Often confused with

Glaze colour · 釉色 · China

mottled blue glaze

A blue glaze broken by pale mottling, named for its likeness to a sea cucumber. Along with white kōchi and Canton ware it is one of the glazes most used for growing trees rather than only showing them — a working glaze with a lot of fine pots in it.

How to tell

• Unstable, varied, with red in the blue points towards gikin — the Yixing line, descended from the Ming Ou kiln, where Ou Ziming of Dingshan worked after Song Jun ware. A white glaze with a little cobalt oxide and iron sand: so unpredictable in the kiln that it produced a whole spread of colours and figures.
• Even, orderly blue mottling points towards deikin — the Canton line from Shiwan in Guangdong, following the Song Guang kiln. Cobalt, chrome, iron sand and red oxide in set proportions, cut half-and-half with white glaze: a stable glaze made for volume.
• A coarse white body under the glaze suggests Canton; a half-porcelain body suggests Yixing.
• Glaze over a shidei or shudei body marks the later Qing Yixing pots, which are kept separate from Ming gikin.

Often confused with

Glaze colour · 釉色 · China

Jun-type sky blue

The sky-blue glaze, and one of the three most familiar glaze colours on Chinese pots. The name it goes by in Japan today is younger than most people assume: it was settled in 1990.

How to tell

• Sky blue is the main register, but the family is wider: sō-kin’yū 草均釉 (grass), ō-kin’yū 黄均釉 (yellow), and a white version that is documented as uncommon.
• Fine vertical streaking is called togō 兎毫, hare’s fur. It is treated as the highest register, because it comes nearest the Jun ware the glaze descends from.
• The same glaze changes over a different body. Laid over a shidei clay it comes out quieter — so two pots can share a glaze and not look related.
• It is a contrast glaze. These pots are most often used against leaf, flower and fruit colour rather than with it.

Often confused with

Glaze colour · 釉色 · China

Lu-jun · patched Jun-type glaze

A Jun-type glaze carrying patches of colour, large and small, across its surface. Despite the old name it is not a kiln — it is a technique.

How to tell

• Patches, not streaks. The mottling is what separates it from plain kin’yū.
• Two bodies, two lineages. Mostly porcelain, from Jingdezhen. But there is a clay-bodied version too, made chiefly at Teizan in Yixing, whose kilns trace back to the Ming Ou kiln and which copied the Jingdezhen glaze — it belongs to the deikin line, the same lineage as Canton namako.
• Unstable early, settled later. The high-fired reduction version begins under Yongzheng and was technically demanding and unreliable; research under Qianlong produced a low-fired version stable enough to carry elaborate work.
• Gold brocade means three layers. Kinran-rokin 金襴呂均 is built up: a black underglaze called ukin, the rokin’yū over it, then gilding on top.

Often confused with

Glaze colour · 釉色 · Japan

copper green

The one Japanese glaze on this page. A copper green, and in the pot world the word is used almost interchangeably with ryokuyū — simply “green glaze”.

How to tell

• A strong glaze with opinions. It is distinctive next to white kōchi or the Jun-type blues, and the practical consequence is recorded: it suits deciduous trees and is difficult with conifers.
• Best with autumn colour, fruit and flower. Among deciduous trees, those are the ones named for it.
• Evergreens can work, quietly. Camellia or chirimen-kazura can settle into a sober unity with it — the one exception recorded to that rule.
• Kiln effect is part of it. Crystalline flecking and mottling both occur; a strongly varied one gets called ao-oribe.

Often confused with

Glaze colour · 釉色 · China

tea-dust glaze

An iron crystalline glaze, olive to brown, finely speckled. China calls it chayemo — tea dust. Japan named it after buckwheat.

How to tell

• Fine crystalline speckle in an olive-brown ground — the quality both names are reaching for.
• A long history behind it. Yellow, green and black versions were being made as early as the Song; later work followed them, with fine pieces particularly in the Ming Chenghua period.
• A green cast is associated with Qianlong, where good suiban of that cast turn up in the bonsai world. Association, not proof — no test goes with it.
• Expect not to find one. There are famous pots in this glaze, but so few overall that the 2007 account describes appearances on the market as extremely rare.

Often confused with

Glaze colour · 釉色 · China

gold-blind glaze

A brownish translucent glaze with specks beneath it that read as gold. Among the imported examples documented here, only a handful are known.

How to tell

• Brown translucent glaze, gold specks below it. The specks are under the glaze, not in it — which is the whole image behind the name.
• Two readings, one word. 金簾 is read either kinren or kinsudare; both are correct.
• Check for a drainage hole. The one documented example appears to be a suiban — a water tray — pressed into use as a planting pot.
• Assume you are wrong first. With this few known examples, a brown speckled glaze is far more likely to be something else.

Often confused with