Cleaning Chawan: How to Properly Care for Porous Ceramics Like Hagi and Shino Ware

A Japanese tea bowl comes without an instruction leaflet. After its first use it sits on the countertop, a greenish rim of matcha on the inside, a fine network of hairline cracks on the outside – and the obvious impulse would be to place it in the dishwater like any other cup. This is exactly where the most common damage originates. A large part of Japanese tea ceramics is open-pored: it absorbs whatever is offered to it and releases it again with the next infusion. Once one has understood this, neither cleaning agents nor complicated rituals are needed, only hot water, a steady hand, and some patience while drying.

Why Japanese tea ceramics react differently than European tableware

European everyday tableware is designed to be dense. Hard porcelain is fired at such high temperatures that the body vitrifies and absorbs practically no water; the glaze additionally seals the surface. That is why a coffee cup survives thirty years in the dishwasher without its material changing. It is, in a sense, sealed shut.

Japanese tea ceramics follow a different logic. Many kilns work with coarser, iron-rich clays and lower firing temperatures, so the body remains permeable. Add to this three particular features. Kannyū (貫入) is the name for the fine network of cracks that forms in the glaze during cooling, because glaze and body shrink at different rates – with Hagi ware, it is the defining feature. Yakishime (焼締) refers to the unglazed high-firing of Bizen and Shigaraki, in which ash and fire alone shape the surface. And the Kōdai (高台), the foot ring, is left unglazed on almost every handcrafted piece, so that the bare clay can be seen. Each of these three spots is an open door.

The basic rules: hot water, a soft sponge, nothing else

The actual cleaning takes half a minute. Rinse the bowl under running hot water right after use, wipe the interior surface with a soft sponge or your bare hand, and set it aside to dry. That's all. Hot water reliably dissolves tea oils and matcha residue as long as they are still fresh - the time between drinking and rinsing is the single most important factor, more important than any product you might use later.

Avoid hard sponge sides, brushes with plastic bristles, and anything abrasive. Even a melamine sponge, which looks so harmless, works like the finest sandpaper and permanently dulls a glaze. Anyone who wants to buy a chawan (tea bowl) and use it for decades is best off getting used to the most minimal approach right from the start: water, warmth, fingertips. With this routine, lime spots and deposits hardly ever form, because nothing gets the chance to dry on.

Why Dish Soap and Fragrances Are a Real Problem in Porous Ceramic Bodies

Dish soap is a guest that leaves again when used on porcelain. In an open-pored ceramic body, it becomes a tenant. Surfactants and fragrances travel with the water into the pores and into the fine cracks of the crackle glaze, where no washing can reach them anymore. With the next hot infusion, the material softens, and part of it returns – as a soapy aftertaste, as a lemon or green apple note over a sencha, as a light film on the matcha foam. Anyone who has ever drunk from a bowl that was cleaned with dish soap for years recognizes the effect immediately.

The same applies to fabric softener on dish towels, scented hand soap, and cleaning agents in the sink. Rinse aid in the dishwasher belongs in this category as well. With unglazed Bizen ware or Shigaraki ware, the effect is strongest, because there is no glaze at all lying between the beverage and the clay. A sake cup made of Bizen ware that smells of citrus cleaner can no longer really be saved, but at most slowly neutralized over many infusions.

Before First Use: Why Porous Ceramics Are Soaked in Water

With Hagi ware and other soft, highly absorbent ceramic bodies, it is customary to soak the piece in water before first use. Place the bowl in lukewarm water for twenty to thirty minutes, until no more air bubbles rise. The reason is simple: a dry, thirsty ceramic body draws hot tea deep into itself, cooling it significantly and absorbing a great deal of color and aroma in a short time. If it is already saturated with clear water, the tea stays where it belongs. Some Hagi bowls even "sweat" slightly through the wall in the first few weeks – this settles down over time.

For particularly porous pieces, Japanese kitchen practice also knows medome (目止め), pore-sealing: the vessel is slowly heated in cold rice water or thin rice starch water, briefly brought to a boil, and left to cool in the pot; the starch settles into the pores. Only one thing matters here: always start cold and heat slowly. Putting a cold piece of ceramics into boiling water is the fastest way to a crack.

Drying: the step where most damage occurs

It is not washing that ruins Japanese tea ceramics, but putting them away too soon. A shard that has absorbed water releases it only slowly – considerably more slowly than the surface would suggest. After rinsing, pat the bowl dry with a soft, unscented cloth and then let it air dry completely: turned upside down or leaned at an angle against a wall, so that air reaches the interior and the unglazed foot ring does not sit in a puddle. A rack or a kitchen grate is ideal for this.

Allow generous time. An ordinary cup is dry after an hour, while a soaked Hagi or Raku ware bowl needs one to three days before even the core has dried through. Only then does it belong in its cloth or in the wooden box. This is precisely where the most common damage to Japanese ceramics occurs: musty odor, foxing, and mold in the shard, because a still-damp piece was placed in a closed box, a plastic container, or a cabinet without air circulation. The smell then sits within the material, not on it.

Hagi no nanabake: when discoloration becomes the true value

After a few months of regular use, a Hagi bowl changes visibly. The tea penetrates the cracks of the crackle, tracing their pattern and gradually transforming the initially whitish, rosy-shimmering glaze into amber and brownish tones. In Japan, this slow darkening carries its own name: Hagi no nanabake (萩の七化け), "the seven transformations of Hagi ware." This does not refer to a fixed number of stages, but to the observation that such a piece takes on a different face several times over the years.

For tea culture, this is not a flaw but the very reason one uses a bowl at all rather than placing it in a display case. A tea bowl seasoned through use tells the story of how often it has been held. Hence perhaps the most important rule of this guide: do not attempt to remove this discoloration. Anyone who tackles it with bleach or scouring cream destroys in ten minutes what took ten years to form – and damages the glaze in the process. A warm, darkening tone is also normal and desired with Shino ware and Raku ware.

What Differs Depending on the Style

Raku ware is hand-built and fired at a comparatively low temperature. The shard remains soft, light, and distinctly absorbent, and the glaze is sensitive to scratches and impacts. Rinse briefly rather than soaking for a long time, never put it in the dishwasher, and use no metal spoons. Ohi ware from Kanazawa, with its warm amber glaze, technically belongs to the same family and is treated the same way. Shino ware carries a thick, milky white feldspar glaze whose surface, with its tiny pinholes and craters, is often compared to a citrus peel. These pores absorb tea but cannot be brushed out – anyone who wants to buy Shino ware should understand the fine inclusions as part of the material rather than as soiling.

Hagi ware has the softest shard and the most pronounced crackle, and consequently requires the most drying time. Bizen and Shigaraki are fired without an applied glaze: high-fired and robust in handling, but open at the surface like stone, which is why dish soap is especially harmful here. Considerably less critical is Japanese porcelain such as Kutani or Imari – densely sintered and easy to wash. Caution is only warranted there for the overglaze colors and the gold decoration, which tolerate neither abrasive cleaners nor the dishwasher, and certainly not the microwave.

Stubborn Deposits, Limescale, and Tea Film

If something has become stuck after all, work with time instead of force. Fill the bowl with hot water, let it sit for an hour, and then wipe it with a soft sponge; dried-on matcha almost always loosens this way. A bamboo spatula or a wooden stick helps at edges the sponge cannot reach. Limescale rings from hard tap water are best wiped away while still moist.

Keep acids away from porous pieces. Vinegar, citric acid, and descalers attack soft glazes and open bodies and lodge themselves in the pores; with dense porcelain they are acceptable briefly and with ample rinsing afterward, but not otherwise. Chlorine cleaners, denture cleaning tablets, baking soda, and scouring cream likewise have no place on a tea bowl. And before you reach for any of these, take a moment to check whether it is really dirt – or already the patina that belongs there.

What You Should Never Do with Japanese Tea Ceramics

No dishwasher: the combination of strongly alkaline detergent, 65 degree water temperature, rinse aid, and pieces clattering against each other is thoroughly unfavorable for handcrafted ceramics, and for gold or overglaze decoration it spells the end regardless. No microwave: moisture in the body heats unevenly and can cause cracks from the inside out. No oven, no freezer, no stovetop, unless the vessel is explicitly made for that purpose.

Also taboo: pouring boiling water into a cold, dry bowl – warm it beforehand with lukewarm water, especially with Raku ware. No soaking for days, because a thoroughly soaked body then barely dries out. No storing while still damp. No stacking bowls inside one another, since the unglazed foot ring acts like a file on a glaze. And never lift a piece one-handed by the rim, but always with one hand underneath; most breakages don't happen during washing, but on the way there.

When Something Breaks After All: Kintsugi Instead of the Trash Can

A crack or a chipped edge does not mean the end of a piece in Japan. Kintsugi (金継ぎ), literally "gold joinery," is the technique of mending broken areas with urushi lacquer and then dusting the seam with gold, silver, or tin powder. The repair is thus not hidden but rather highlighted – the break then becomes part of the object's biography. This is labor-intensive from a craft perspective, because each layer of lacquer must cure for days to weeks in a humid environment.

For everyday life, this above all has one practical consequence: keep all shards, even the smallest ones, and do not glue anything provisionally with super glue. Synthetic resin is difficult to remove later and makes a proper restoration considerably more difficult. A bowl wrapped in a cloth in a cabinet will wait patiently until you have found a workshop.

A Bowl That Grows More Beautiful With the Years

In the end, caring for Japanese tea ceramics takes less work than for any other tableware. No cleaning agent, no dishwasher cycle, no polish – just hot water, a soft sponge, and a place where the bowl can dry undisturbed. The rest is use. And it is use that gradually turns a new piece into a personal one: the crackle that becomes a little more distinct week by week, the rim you always drink from, the warm tone on the inside.

At densho.de you will find handcrafted tea bowls, sake and yunomi bowls as one-of-a-kind pieces that we personally purchase in Japan – from soft Raku ware and Ohi ware to Shino and Oribe, to unglazed Bizen and Shigaraki. Anyone who wants to buy Hagi ware gets something with it that hardly any other material offers: an object that changes with use. Don't put it in the display case. Put it next to the kettle.