Japanese Pottery Glazes: An Introduction
Two tea bowls of the same shape can sit side by side and still differ in colour — piece by piece, and maker by maker. That is much of the appeal of japanese ceramics. One is deep blue; the other, a warm amber.
What decides this difference in colour is the glaze (yuyaku) — the glassy film that covers the surface of a piece. A glaze does more than give colour: it strengthens the piece against water, makes it more durable, and creates the very texture that meets the hand of the person using it. It is no exaggeration to say that much of the impression a piece of japanese pottery makes is decided by its glaze.
This article explains what a glaze is, how to recognise the main glaze types, and the pleasure of choosing a piece by its glaze. By the end, you should be able to pick up a piece and know: “this is oribe,” or “this crazing will age beautifully.”
What Is a Glaze?
A Glassy Film That Covers the Piece
A glaze is a material applied to the surface of a shaped and bisque-fired piece, which turns glassy when fired at high temperature. In English it is called simply “glaze”; in Japanese, yuyaku.
A piece fired from clay alone has a surface full of fine pores. Left that way, it absorbs water and takes on odours. Apply a glaze and fire it, and the surface melts into a film of glass — waterproof, resistant to staining, and easy to wash. A glaze was, first of all, a practical technology.
But it did not stop there. The trace metals in the raw materials produce unexpected colours in the flame. The same glaze changes its expression depending on how thickly it is applied and where it sits in the kiln. This impossibility of full control is what carried glaze out of the realm of practical technique and into the realm of beauty.
What a Glaze Is Made Of
The basic materials of a glaze fall into three groups.
① Feldspar — the main component, which forms the glassy skeleton. This is what melts at high temperature and becomes glass.
② Ash and limestone — feldspar alone would require temperatures approaching 1,500°C, so these lower the melting point. Ash from burnt plant matter (wood ash, straw ash) has been used since ancient times. The type of ash also changes the colour.
③ Metals (colourants) — the components that decide colour. A very small quantity changes the result dramatically.
| Metal | Colour produced |
|---|---|
| Iron | The blue-green of celadon, the yellow of kiseto, the black of tenmoku, amber |
| Copper | The green of oribe, the red of shinsha |
| Cobalt | The indigo of sometsuke, the deep navy of ruri |
| Titanium, manganese | Ochre, dark brown, crystalline effects |
What is fascinating is that the same iron produces completely different colours. In small quantities iron turns blue-green; in larger quantities, black. The quiet blue of celadon and the deep black of tenmoku — these two opposites are born from the same metal. And beyond the components of the glaze itself, the minerals in the clay body also greatly alter how the colour emerges. Glaze, clay, and the oxidation or reduction described below work as a set, and together they create the distinctive character of each ceramic artist’s work.
Wooden drying racks of unfired japanese pottery in a potter’s studio, with glaze buckets and tubs on the floor
The Air of the Flame Changes the Colour: Oxidation and Reduction Firing
The other element that decides the colour of a glaze is the air inside the kiln during firing. The way air meets the piece during firing greatly changes the colours that emerge from the components of the glaze.
Oxidation firing (sanka shosei) — firing while feeding the kiln plenty of oxygen. Glazes develop warm colours: russet, yellow, bright green.
Reduction firing (kangen shosei) — firing with the oxygen restricted. Starved of oxygen, the flame draws it out of the clay and the glaze instead. Through this action iron shifts towards blue-green and copper towards red, producing the cool, clear colours of ash-blue and celadon. Blue pieces are most often fired this way. And as oxygen is drawn out of the clay, the minerals held in that clay change the colour further still.
With the same clay and the same glaze, this difference in air alone produces a different piece. This is why celadon can only be born in reduction. When a ceramic artist watches over the temperature and the air of a kiln for days on end, it is because everything rests on this one point.
Electric kiln with its door open, shelves of glazed plates stacked inside on kiln furniture
How a Glaze Is Applied Changes Its Expression
A glaze also changes its expression greatly depending on how it is applied. When you look at a piece, try to find the traces of that application.
Dipping (tsukegake) — the most basic method, immersing the whole piece in liquid glaze. The finish is even, though the points held by the fingers take no glaze and those marks can remain. Some ceramic artists deliberately leave these fingermarks as keshiki — natural markings to be appreciated.
Ladle pouring (hishakugake) — pouring glaze from a ladle over the piece. The path the glaze takes becomes the pattern itself, holding both momentum and chance.
Glaze poured from a ladle over a japanese pottery plate, the dark glaze running off its rim into a bucket
Spraying (fukigake) — applying the glaze as a fine mist, which allows gradations of density.
Divided glazing (kakewake) — applying two or more glazes to a single piece. Where they meet, the glazes melt into one another and unexpected colours appear.
Wax resist and sgraffito (ronuki, kakiotoshi) — repelling the glaze from areas protected with wax, or scraping the applied glaze away to reveal the body beneath, to draw a pattern.
There is also the choice not to glaze at all. Yakishime — unglazed high-fired stoneware, represented by Bizen ware and Shigaraki ware — uses no glaze whatsoever and is instead fired hard at high temperature. Even so, a natural ash glaze appears on the surface, where wood ash has settled and melted. It is a glaze applied not by a person, but by the kiln.
Unglazed yakishime japanese pottery in close-up, the clay marked with orange-red flame colour and scorching
Recognising the Main Glazes by Colour
From here, we introduce the principal glazes by colour, so that you can name them when you have a piece in your hands.
Blue Glazes
Celadon (seiji) — a clear colour ranging from blue-green to pale blue, born from reduction firing a glaze containing a trace of iron. Originally a Chinese technique, it was carried on in Japan by Nabeshima ware and Kyoto ware. The appeal of celadon lies less in the colour itself than in its depth. Where the glaze pools thickly it is dark; where it thins, it pales; and the expression shifts with the fall of light. Many celadon pieces develop fine crazing, and time accumulates within those lines.
Deep blue-grey glazed japanese pottery bowl in close-up, its surface covered in fine crazing with a pale pooled centre
Sometsuke / gosu — a technique in which designs are painted onto a white body with a cobalt pigment, then covered with a clear glaze and fired. Patterns drawn in indigo alone appear to sit beneath a transparent film. It is the representative expression of japanese porcelain regions such as Arita, Hasami and Tobe. Gosu is the pigment used for the painting, and the foremost example of underglaze decoration.
Ruri glaze (ruriyu) — cobalt mixed into the glaze itself, dyeing the whole piece a deep navy. A night-sky darkness that becomes strikingly opulent when combined with gold.
Green Glazes
Oribe — a vivid deep green from a copper-bearing glaze. It is a Mino glaze born in the Azuchi-Momoyama period from the aesthetic sense of the tea master Furuta Oribe. The essence of oribe lies in a bold composition: rather than glazing the whole piece green, only part is covered in green, and the rest is painted with iron designs. Asymmetry, distorted forms, deliberate disruption — revolutionary for its time, and avant-garde still. The gradations of green, and the depth where the glaze has run and pooled, are what to look for.
Ash glaze (kaiyu) — the oldest glaze of all, made principally from plant ash. It develops from pale yellow-green to olive, giving a plain, settled impression. It is the glaze that sits most naturally on everyday japanese tableware.
White Glazes
Shino — a glaze based on feldspar; the first white glaze born in Japan, and a product of Mino. The white of shino is not the pure white of porcelain but a thick, generous white carrying a faint blush of red or yellow. Countless fine pits open across the surface — a texture called yuzuhada, “citron skin” — and the iron in the body shows through in red as hiiro, flame colour, which becomes the keshiki. Held in the hand it feels soft; against the lips it feels warm. Shino is a glaze to be touched as much as to be looked at.
Kohiki — a white slip applied over a dark, iron-bearing clay, then finished with a clear glaze. The result is a soft, milky white through which the colour of the clay beneath shows here and there. Kohiki absorbs water readily, and stains from tea and soy sauce enter the surface as keshiki the more it is used — making it one of the glazes that “grows” most of all.
Pale celadon-white glazed plates drying on a board in the studio, their glossy surfaces catching the light
Hakeme — a technique in which white slip is applied with a coarse brush and the brush marks are left exactly as they fall. Vigorous white streaks run across the piece.
Yellow Glazes
Kiseto — a pale, subdued yellow obtained by oxidation firing an ash glaze. It is a representative Mino glaze. The surface has a quiet, matte quality, and the finest examples are said to have aburageda, a “fried tofu skin” texture. Green speckles (tanpan) and scorched iron bleeds add keshiki to an otherwise still piece.
Black and Brown Glazes
Tenmoku / iron glaze — black to blackish brown, from a glaze rich in iron. The name derives from the tea bowls used at the Zen temples of Mount Tianmu in China. Tenmoku can undergo remarkable transformations: yuteki, “oil spot,” where the iron in the glaze crystallises into speckles, and yohen, where iridescent light appears depending on the angle. Yohen in particular, with only a handful of intact examples said to survive in the world, is the summit of glaze.
Amber glaze (ameyu) — a translucent amber obtained by applying an iron glaze thinly and firing in oxidation. As the name suggests, it is a lustrous brown reminiscent of malt syrup. Lighter than tenmoku, it is widely loved as a colour that sits easily on everyday japanese pottery.
Red Glazes
Shinsha — a red to red-purple born from reduction firing copper. The same copper turns green in oribe and red in shinsha. The transformation is extremely unstable, and the colour vanishes if the kiln conditions shift even slightly. Not even the ceramic artist knows the result until the piece comes out of the kiln — it is one of the most difficult glazes of all.
Akae — a technique of overglaze decoration in which a glazed and fired piece is painted in colours dominated by red, then fired again at low temperature. It is the brilliant world of coloured painting represented by Kutani ware and the Kakiemon style.
Imari porcelain plate painted in red, indigo and green florals, resting on a lacquered tray beside dried flowers
Glazes That Appear as Surface Change
Crazing (kannyu) — the fine cracks that enter the surface of a glaze because the glaze and the clay body contract at different rates. These are not breaks. They do not affect the strength of the piece, and in Japan they have long been appreciated as keshiki. They are conspicuous in Hagi ware and in celadon. As the piece is used, tea and coffee seep in and the lines of the crazing rise more darkly — a change known as keinen bika, beauty that deepens with the years.
Bidoro — where ash has settled thickly in a wood kiln, melted, and pooled in a vivid, glass-like green. The name comes from the Portuguese vidro, “glass.” It is prized in Iga ware and Shigaraki ware.
Crystalline glaze (kesshoyu) — a glaze in which crystals precipitate during cooling, so that flower-like patterns rise to the surface. No two are ever the same shape.
Choosing Japanese Pottery by Glaze
Here is the heart of the matter. The aim is not to memorise the names of glazes. The aim is to become able to choose pieces that suit your own life. We will consider it from three points of view.
1. Choose by What You Will Serve
A piece is not complete on its own. It is completed when food is placed in it. The colour of a glaze can lift the colour of a dish — or kill it.
| Glaze | Dishes it flatters | Why |
|---|---|---|
| White (shino, kohiki) | Almost anything; especially simmered dishes, dressed vegetables, seasonal produce | Suits any colour and lets the food’s own colour stand. Ideal as a first piece |
| Celadon, sometsuke | White fish, tofu, somen noodles, fruit | Cool and clear, and beautiful against pale ingredients. Strong on a summer table |
| Black (tenmoku, iron glaze) | White rice, fish cakes, brightly coloured dishes | Lifts whites and warm tones to the maximum; the piece recedes into background |
| Amber glaze | Simmered dishes, fried food, root vegetables, soups | Harmonises with brown-toned food in the same register. Brings warmth |
| Oribe | Pale dishes, sweets, food served with sake | The green is strong, so fewer colours in the food make it work |
| Kiseto | Dressed vegetables, pickles, small portions with sake | Understated, and makes a small serving look refined |
The principle, when you cannot decide, is this: when the food is rich in colour, let the piece be quiet; when the food is poor in colour, let the piece speak. Choosing white (kohiki or shino) as a first piece rarely goes wrong.
2. Choose by Whether You Want Change
There are two kinds of pieces: those most beautiful on the day you buy them, and those that grow more beautiful the more they are used.
Porcelain sometsuke and ruri glaze belong to the first kind. The beauty of the day you bought it is held, unchanged, ten years later. Clean, stable, and equal to the daily life of a family.
Kohiki, Hagi ware and crazed pieces belong to the second. A kohiki piece so white it seems almost plain will, after a year, show brown mottling, and after three years will have settled into an overall amber. This change is called keinen bika. Two people who buy the same piece will, three years later, own entirely different pieces. How it was used becomes, directly, the expression of the piece.
Neither is superior. But if you buy without knowing which of the two you want, you may find yourself puzzled later.
3. Choose by Who Made It
Last, and perhaps most important of all.
“Celadon,” “oribe,” “kohiki” — these are the names of techniques, not the names of works. The same celadon becomes an entirely different blue in the hands of a different ceramic artist. The recipe of the glaze, the thickness of its application, the temperature and duration of the firing, where in the kiln the piece is placed — all of these are the artist’s judgement, and their accumulation makes that person’s blue.
One artist fires celadon in a pale tone close to white. Another pursues a deep, green-cast blue. Bound together by the same phrase — “a celadon tea cup” — they are, in the hand, quite different things.
So when you are choosing among the pieces you have found by searching the name of a glaze, look one step further, to who made it. Why that person pursues that colour, and in what kiln they fire it. A piece chosen with that understanding is no longer simply “a celadon tea cup.” It is the one piece that you chose.
Where to Buy Japanese Pottery by Glaze Online
Looking for authentic japanese pottery for sale, chosen by its glaze? At Nokaze we carry the work of ceramic artists devoted to each of these glazes — celadon, oribe, shino, kohiki, tenmoku, amber. Every piece comes with the name of its maker and that maker’s own words. Even within “celadon,” you can see whose blue it is before you choose.
Which colour belongs on your table? Whether you are looking for japanese gift ideas or beginning a collection of your own, start simply by looking at the pieces.
Browse japanese pottery at Nokaze →