Makers · 作家 · Tokoname
Koyo
鴻陽b. 1944
A tile-maker's son who was pointed toward Chinese antique pots — and one glaze in particular — by a nurseryman, and built a kiln on the strength of it. Fifty years on, Koyo is known above all for glaze, and for a green that people compare to Tofukuji's.
At a glance
Drawn from the standard Japanese survey of bonsai ware and checked against pots we have handled.
- Art name
- Koyo 鴻陽
- Real name
- Koichiro Aiba 相羽鴻一郎
- Born
- 1944
- Region
- Tokoname, Aichi 常滑
- Generation
- Third in the trade
- Kiln
- Koyo Toen 鴻陽陶園, founded 1970
- Specialism
- Glaze
- Also works in
- Tableware, objects, wall tile
- Successor
- Juko, his son
01 · 転身 The turn
From wall tile to bonsai pots
The family business was tiles. Koichiro was set to continue it, and for a while he did.
Around 1968 a nurseryman changed his direction: Takeyama Bozo of Fuyoen suggested he look at Chinese antique pots, and at kin-yū glaze in particular. He took the suggestion seriously enough to make it a research project, and then a trade. In 1970 he opened his own kiln under the name Koyo Toen.
タイル製造から、中国古鉢と均釉の研究へ。
02 · 緑釉 The green
A green measured against Tofukuji's
Koyo's reputation rests on glaze. Large or small, glazed or unglazed, the survey notes a particular inventiveness in his work — but it is the depth of his understanding of glaze that gets singled out.
One comparison in particular is worth knowing. His green — Oribe — is described as calling to mind the green of Heian Tofukuji: the standard against which greens in this field are measured. That is not a small thing to have said about you.
“The green that recalls Tofukuji's.”
The same green went on to his son. On Juko's hexagonal pot the survey calls it the family green — a formula handed down rather than reinvented.
03 · 落款 The seals
Five marks, and one that means something else
Koyo used a fan-shaped seal for the small pots he has concentrated on in recent years, and a square stamp besides. Two further marks give the kiln name.
The fifth is the interesting one. A mountain-shaped mark sitting above the others is not a maker's signature at all — it reads 芙蓉園撰: selected by Fuyoen, the nursery of the man who set him on this path.
| Mark | Reading | Note |
|---|---|---|
| 鴻陽 | Koyo — fan-shaped seal | Used on the small pots of recent years. |
| 鴻陽 | Koyo — square stamp | A second form of the same name. |
| 鴻陽造 | Koyo zō | “Made by Koyo.” |
| 鴻陽陶園 | Koyo Toen | The kiln name. |
| 芙蓉園撰 | Fuyoen sen — mountain-shaped mark | Not a maker’s mark: “selected by Fuyoen”, the nursery of his mentor Takeyama Bozo. |
Why a selection mark matters
A selection mark records that someone with standing in the field judged this pot good enough to put their name to. It is a different kind of evidence from a maker's signature, and worth looking for.
Photographs of these marks on pots from our own stock will be added here. A mark in the hand rarely looks like a printed plate — clay, glaze pooling and wear all change it.
04 · 代表作 Documented works
Pieces recorded in the literature
Not for sale — the reference pieces published in the standard Japanese survey.
| Work | Size (cm) |
|---|---|
| Oribe-glazed rectangle with kiln effects, outer rim | 48 × 36 × 12 |
| Oribe-glazed cut-corner rectangle, outer rim | 12.5 × 10 × 3.5 |
| Oribe-glazed oval with applied flower relief | 16 × 12.5 × 3.5 |
| Unglazed hand-built boat form | 13.5 × 10.5 × 4.5 |
| Soba-glazed rectangular water tray | 39 × 26 × 3.3 |
05 · 広がり Beyond pots
Not only bonsai ware
Koyo has never worked only on pots. Tableware, wall tiles and more sculptural pieces all come out of the same kiln, and he is known within the wider ceramic world for his research into lustre glaze. The awards are numerous.
In recent years he has also turned to producing small glazed pots by volume methods — a deliberate choice to keep good pots within reach.
06 · 用語 Glossary
The words on the label
- 織部釉 Oribe-yū
- The classic Japanese green glaze.
- 均釉 kin-yū
- The Chinese-derived glaze he first studied.
- 蕎麦釉 soba-yū
- Buckwheat glaze — a dry, oatmeal-toned surface.
- 窯変 yōhen
- Kiln effects — colour shifts caused by the firing itself.
- 撰 sen
- “Selected” — as in a connoisseur’s selection mark.
- 水盤 suiban
- A shallow tray, used for water plantings and displays.
Available
Koyo pots in the collection
We handle Koyo regularly. Each pot is 一点物 ittenmono — one of one — and ships worldwide from Tokyo.
Sources
盆器大図鑑【上巻】 Bonki Daizukan, Vol. 1, p. 157–158. Checked against pots handled by YAKUMO JAPAN. Last verified 18 July 2026.
Where the record is unclear we say so rather than guess.