Kogei What the listing does not tell you
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Porcelain in the dishwasher: the body is fine, the decoration may not be

The porcelain body is not what the dishwasher threatens. The decoration is — and whether it is under the glaze or on top of it decides the answer.

Does this apply to yours?Look at the surface, not the pattern. Underglaze decoration sits beneath the glaze, which is why the source describes it as producing a surface with a uniform sheen — the pattern is under the same continuous gloss as the bare porcelain beside it. Overglaze is applied on top of that fired glaze, so the decorated areas and the undecorated ones are not the same surface.

Own something else Japanese? Check what will destroy it →

Under the glaze, or on top of it

Wikipedia’s articles set out the two methods. Underglaze decoration is painted on before the transparent glaze is applied and fired; because the glaze then covers it, the decoration is completely durable and the surface has a uniform sheen. Overglaze decoration is applied on top of the already fired and glazed surface and fixed in a second firing at a relatively low temperature — which is what allows its wider, more vivid palette, since those pigments would not survive the temperature the porcelain body needs.

That lower second firing is the whole story. The colours fuse onto the glaze rather than under it, so they are exposed to whatever the surface is exposed to. Blue-and-white porcelain is the classic underglaze case, historically limited to a narrow range of colours — cobalt blue above all — precisely because few pigments survive the high firing. A piece with a broad, bright palette is more likely to be carrying it above the glaze.

Gold is always on top

Gold and metallic rims are the sharper case, because gilding is applied over the glaze by nature — there is no underglaze gold. That is also why gold-rimmed pieces are the standard exception to microwave use: metal in a microwave is a separate problem from wear. And the porcelain body itself is genuinely tough, described as completely vitrified, hard and impermeable even before glazing, which is why the answer is about the surface rather than the material.

How these pages are put together. Written in Japan by an engineer — twenty years in manufacturing, in metal, surfaces and finishing. That is the whole of the expertise claimed here: it is why these guides care which material and which millimetre, and it is not the same thing as being a craftsman or a tea specialist. We do not own or test the pieces described here — the facts are compiled from makers, specialist retailers and published sources, and every one is listed at the foot of the page so you can check it yourself. Where sources disagree, the page says so rather than picking the tidier number. Makers do change specifications, so confirm against the listing or the manual before buying. If something here is wrong, tell us and it gets corrected.

Where to look

Listings rarely say “overglaze” or “underglaze” outright, but they often say enough: hand-painted enamel and a wide bright palette point one way, blue and white and a single cobalt point the other. If the piece is in front of you, the sheen tells you more than the description does. And where a maker states dishwasher suitability, that is the answer for that piece — it is their decoration and they know which side of the glaze it is on.

No shop link here. This is a question about a piece you already own or are looking at, and the check costs nothing. The lacquerware guide below is the other half of the same table: urushi and the dishwasher is a shorter conversation.

Sources

The other guides

Agarwood: the fake has a tell

The scent exists because the tree was infected. Uninfected wood is pale and light — whatever was added.

What a whetstone grit number does not tell you

There is no dominant standard behind the number. Two #1000 stones can cut differently.

The board decides how long the edge lasts

Glass dents, rolls and chips edges rapidly. Wood is self-healing — but grain matters more than "hardwood".

Santoku, gyuto, bunka, nakiri — and which is handed

Two of these are the same knife. And a nakiri suits either hand; the usuba it resembles does not.

Washi: what the word covers

JIS defines it — and the definition says most washi today is machine-made from chemical pulp.

A matcha whisk is one piece of bamboo

Carved from a single piece, so a snapped tine is not a repair. The tine count is a spec, not a score.

Goat hair or synthetic, for a Kumano brush

Not a quality ladder. Natural hair holds powder; synthetic is built for cream and liquid.

“Ceremonial grade” is not a standard

ISO and Japanese labelling define how matcha is made. Neither defines a grade.

A single-bevel knife is made for one hand

Ground on one side only. The wrong side does not cut badly — it does not work.

White steel or blue: which carbon steel

Blue holds an edge longer and is harder to sharpen. Which is better depends on how often you sharpen.

Rust or patina: which one are you looking at

One protects the blade, the other eats it. Scrubbing the wrong one leaves the knife worse off.

What HRC on a knife listing buys you

Western knives sit at 52–58 and 20–22°; harder steel is what permits 15–18°. Higher is a different bargain.

A chipped knife: cause, and what repairs it

Repair is subtraction — grind past the chip on a coarse stone, then work back up the grits.

Giving a knife: the belief, and the coin

A gifted knife is said to sever the relationship. The custom is that the recipient hands back a coin.

The handle: porous, replaceable, sometimes handed

Friction-fitted, not bonded — so it can be replaced. And a D-shaped handle is made for one hand.

Mould on a bamboo steamer, and the answer English guides skip

The usual fix starts by soaking it. A seiro maker calls soaking strictly forbidden.

What destroys lacquerware

Dishwasher, microwave, sunlight. All normal, all irreversible on urushi.

Is urushi safe to eat from?

Uncured urushi gives most people a rash. Cured, reactions are possible but less common.

Urushi and bacteria: what was actually measured

A prefectural institute put eleven lacquer films through JIS Z 2801. Most came back undetectable.

Is a Damascus knife real? The word changed

The original ceased production around 1900. Since 1973 the word has meant pattern welding — decoration.

What a donabe is actually doing

It conducts heat badly. That is the product — and it is also why it cracks.

The step before a new donabe cooks anything

Unglazed clay is porous until rice starch seals it — one simmer, once.

Why a donabe does nothing on induction

Induction heats metal, not clay. Most donabe never get warm — and cannot be converted.

What is actually in a kintsugi kit

Real urushi cures in a humid box over days to weeks. A kit that sets in an hour is something else.

Eating from a kintsugi repair: what actually decides it

Not urushi against epoxy. Whether the material states food-contact compliance.

Japanese chopsticks: the point, and two gestures

Pointed where Chinese ones are blunt. And two ordinary gestures read as funeral rites.

Sumi or India ink: the binder decides

Sumi is soot held by animal glue. India ink needs no binder and dries waterproof on its own.

Tetsubin or tetsu-kyusu?

One boils water and gives you iron. Putting the other on heat cracks its lining for good.

Rust inside an iron kettle: the fix people look for is the damage

The spots appear in the first week. The makers’ association says do not take them off.

How much iron does an iron kettle actually give you?

The form is settled by a 2003 paper. The amount is not settled by anything.

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