Our Glazes & Making

Sayado Wadagama (道祖土和田窯) works with six traditional glazes of Mashiko. We mix each one ourselves and adjust the recipe until it gives the color we intend. This page explains what each glaze is made of, why our two-color pieces are harder to make than they look, and how a piece takes shape in our workshop in Sayado, Mashiko.

Six glazes from Mashiko

Glaze is a coating made from stone, ash, and clay. In the kiln it melts into a layer of glass, which makes a pot stronger, keeps water out, and helps it resist stains. Changing the balance of those materials changes the color and surface of the glaze. These are the six we use.

Kaki (柿釉, persimmon glaze)

Kaki is the glaze most closely tied to Mashiko. It is made from ashinuma stone, quarried in the north of the town. The stone is ground, roasted at a high temperature, and then mixed with water. In the heat the powder turns red, which is why potters here call it akako, "red powder." The stone is rich in iron, and Kaki fires a deep red-brown. Its name, kaki, means persimmon and is said to come from the color of dried persimmons.

Kaki also holds heat and resists water better than other glazes. For that reason it has been used on roof tiles in snowy parts of Japan, especially Tohoku in the northeast, where red-brown roofs can still be seen.

Nuka (糠釉, rice-husk ash glaze)

Nuka is an ash glaze. We make it with ash such as rice husk, rice straw, and wood, and it fires to a milky white.

Nami-jiro (並白釉, standard white glaze)

Nami-jiro is made mainly from limestone. Its name means standard white, but it fires clear, so the clay underneath shows through. In Mashiko it is also used as a base glaze.

Kuro (黒釉, black glaze)

Kuro is rich in iron and fires black. Its surface depends on how it is fired. With plenty of oxygen in the kiln, called oxidation firing, it comes out rough to the touch, a texture known as yuzu-hada, or yuzu skin. With the kiln starved of oxygen, called reduction firing, it turns a glossy black.

Seiji (青磁釉, celadon glaze)

We make Seiji by adding copper to Nuka, and it fires to a deep blue. Celadon on porcelain tends to be clear and glassy. Mashiko's Seiji sits thick on the pot, in a deep blue of its own.

Ame (飴釉, amber glaze)

Ame is a clear, amber-brown glaze. It is usually made by adding manganese oxide to Nami-jiro. Ours is made the traditional Mashiko way: we mix ashinuma stone, the same stone we use for Kaki, with wood ash. The ash thins out the iron in the stone, which is what turns the glaze brown.

Mixing for the color we want

We mix each glaze for the color we are aiming at, so color changes that happen by chance in the kiln are rare in our pieces.

Two glazes on one piece: 2tone

Our 2tone series puts two glazes on each piece, one on each half. On the mugs, one glaze covers the top and another the bottom. It looks simple, but the glaze work behind it is particularly demanding.

2tone uses four of our glazes: Nuka, Kuro, Ame, and Seiji. Each melts at a different temperature, yet two of them have to share one piece. With four glazes there are twelve ways to pair them, one on each half, and the series comes in all twelve. It takes careful mixing and adjustment of every glaze.

Where the two glazes meet, they overlap, and the line between them wavers. It wavers differently every time, so no two pieces are the same.

From clay to kiln

These are the main steps in our workshop.

Wedging the clay

Before clay can be shaped, it has to be kneaded. How firm it needs to be depends on how the piece will be made, so we knead it by machine or by hand to suit the piece.

Throwing on a kick wheel

Our craftspeople shape pots on a traditional kick wheel, which is turned with the foot. On our 2tone mugs, each handle is attached by hand, so no two handles are quite the same, just as no two people's fingers are.

Trimming by hand

The finer details of each piece are then trimmed by hand.

Glazing

Each piece is fired once at about 800°C before it is glazed. This first firing is called the bisque firing. Where glaze must not go, we paint on wax, on some pieces with a brush, so the glaze is repelled there.

Firing

The glaze firing goes above 1,200°C, hot enough to melt the glaze. Most of our pottery is fired in a gas kiln of four cubic meters, and we choose oxidation or reduction firing to suit each piece.

Seeing and buying our pottery

You can see our pottery in person at Toko Gallery in Mashiko. This online shop delivers within Japan only. If you live outside Japan, please see Where to Buy & Care.