金継ぎのキット
Kintsugi is repair with urushi lacquer and precious metal powder. Much of what is sold as a kintsugi kit is something else, and the difference decides whether the bowl can be used.
Wikipedia defines kintsugi as repairing broken pottery by mending the breaks with urushi lacquer dusted or mixed with powdered gold, silver or platinum. It names the materials: ki urushi, the pure urushiol-based lacquer; bengara urushi, iron-red urushi; mugi urushi, half ki urushi and half wheat flour; and sabi urushi, ki urushi mixed with two kinds of clay. The repaired piece then rests in a furo — a humid box, traditionally a wooden cupboard with bowls of hot water — at 90 per cent humidity for between two days and two weeks while the urushi hardens.
That curing requirement is the useful part, because it is a property no substitute shares. Urushi hardens by oxidation and polymerisation in the presence of moisture, which is why it needs the humid box and the weeks. An adhesive that sets quickly in dry air is curing by a different mechanism entirely — it may make a perfectly good repair, but it is not the material the word describes, and it will not behave like it.
There is also a hazard worth knowing before you open a jar. Urushi is urushiol-based, and urushiol is an allergen: in most people it causes an allergic skin rash on contact, urushiol-induced contact dermatitis. It is the same compound that makes poison ivy and poison oak what they are — the lacquer tree is in the same family. Uncured urushi is handled with gloves for that reason.
Kit listings tend to lead with the gold. The two things worth finding instead are the base material — whether the word urushi appears at all, and whether the gold is metal powder or a pigment — and the curing instructions, which give the material away regardless of what the description claims. A kit that ships with a humidity box is telling you something; a kit that promises a repair in an afternoon is telling you something else.
No shop link on this page, and here the reason is unusually concrete: choosing a kit would mean taking a position on the food-safety question above, which this site cannot source. The lacquerware guide below covers what urushi is and what destroys it.
Sources The other guides鉄瓶と鉄急須
One boils water and gives you iron. Putting the other on heat cracks its lining for good.
土鍋の目止め
Unglazed clay is porous until rice starch seals it — one simmer, once.
漆器の手入れ
Dishwasher, microwave, sunlight. All normal, all irreversible on urushi.
片刃と利き手
Ground on one side only. The wrong side does not cut badly — it does not work.
土鍋とIH
Induction heats metal, not clay. Most donabe never get warm — and cannot be converted.
熊野筆の毛
Not a quality ladder. Natural hair holds powder; synthetic is built for cream and liquid.
砥石の番手
There is no dominant standard behind the number. Two #1000 stones can cut differently.
茶筅の穂数
Carved from a single piece, so a snapped tine is not a repair. The tine count is a spec, not a score.
錆と経年変化
One protects the blade, the other eats it. Scrubbing the wrong one leaves the knife worse off.
三徳・牛刀・菜切
Two of these are the same knife. And a nakiri suits either hand; the usuba it resembles does not.
ダマスカスの意味
The original ceased production around 1900. Since 1973 the word has meant pattern welding — decoration.
白紙と青紙
Blue holds an edge longer and is harder to sharpen. Which is better depends on how often you sharpen.
抹茶の等級表示
ISO and Japanese labelling define how matcha is made. Neither defines a grade.
硬度と刃角
Western knives sit at 52–58 and 20–22°; harder steel is what permits 15–18°. Higher is a different bargain.
まな板と刃
Glass dents, rolls and chips edges rapidly. Wood is self-healing — but grain matters more than "hardwood".
刃物を贈るとき
A gifted knife is said to sever the relationship. The custom is that the recipient hands back a coin.
沈香と伽羅
The scent exists because the tree was infected. Uninfected wood is pale and light — whatever was added.
箸の形と作法
Pointed where Chinese ones are blunt. And two ordinary gestures read as funeral rites.
墨と膠
Sumi is soot held by animal glue. India ink needs no binder and dries waterproof on its own.
柄の木と嵌合
Friction-fitted, not bonded — so it can be replaced. And a D-shaped handle is made for one hand.
釉の上か下か
The body is impermeable. It is the decoration that is exposed — and you can feel which kind it is.