一What you need
- Cotton gloves — or clean, dry hands and the edge of the coin. Skin leaves salt and oil; on plated metal both come back as fingerprints in a year.
- A paulownia box or tray — kiri holds humidity steady and gives off none of the acids that oak, cedar or plywood do.
- A soft tenugui to set a coin on, and a loupe to look at it properly, which is most of the pleasure.
Boxes, tray, cloth and loupe are in the collection. No dips, no polish, no ultrasonic baths, no toothbrushes — ever. They strip the patina; nothing puts it back.
二Handling
Hold a coin by its edge, between thumb and forefinger, over a cloth. Never by the faces, never over a stone floor. An ōban is held with both hands, flat, like a tray. Put it down on the tenugui, not on the desk.
三The rule
Do not clean it. Not with a cloth, not with water, not with anything sold as gentle. The dark in the recesses and the bright on the high points took us hours per piece and would have taken history two centuries. A cleaned coin is a new coin, and a new coin is worth what its metal is: very little.
四Dust and fingerprints
If a coin has been handled, breathe on it and let it dry; that is all a fingerprint needs while it is fresh. Dust lifts with a soft, dry brush, held like a pen, in one direction. If a mark will not leave with that, leave the mark.
五Where it lives
In its kiri box, lid closed, in a drawer or on a shelf away from sun and radiators. Forty to fifty-five percent humidity is the room a coin likes; a paper packet of silica gel in the drawer will hold it there. Gold and silver plated pieces may share a box; copper coins prefer their own.
六What kills a coin
Never: PVC sleeves and albums (they sweat a green film into the metal within a few years), rubber bands, damp basements, direct sun on a framed piece, coins rattling loose in a drawer, and any product with the word 'polish' or 'restorer' on it. Each of these costs more than a decade of honest keeping.
Paper, cotton, silk and paulownia only. If a coin touches something, it should be one of those — nothing else.
七Display
A framed koban goes on a wall that never gets afternoon sun. A loose coin on a stand goes under a glass dome, or it will need the brush every week. Rotate what you show: a coin in the dark for a season keeps its colour longer than one on the shelf all year.
八When to send it to us
Plating that lifts, a box that splits, a green bloom you did not put there — write to hello@sukihagane.com. Some repairs belong on a workshop bench, not a kitchen table, and we would rather re-age a piece than see it scrubbed.