By Rafe Calder
The Japanese house of old had no central heating, and the kotatsu is what people did about it. A frame, a quilt, a heat source underneath, a top over the lot. You sit on the floor and put your legs in.
What it is
Wikipedia defines a kotatsu as a low, wooden table frame covered by a futon or heavy blanket, with a tabletop on top and a heat source underneath: formerly a charcoal brazier, now electric, often built into the table. It says kotatsu are used almost exclusively in Japan. JeePe, a Japan travel and lifestyle site, gives the same three parts: a table base with a tabletop, a kotatsu futon and a heater unit. It stresses that the kotatsu heats the lower body rather than the whole room.
A heater on the old hearth
Both sources trace the origin to the irori, the sunken cooking hearth. Wikipedia places the beginning in the Muromachi period, in the fourteenth century, when a seating platform was added to the irori and a quilt, called an oki, held in the heat of the charcoal. It names that early form hori-gotatsu, “dug kotatsu”. In the seventeenth century, it says, the floor around the irori was dug out in a square, with a platform built around it.
JeePe says the origin is believed to be that people built a wooden frame, a yagura, over the irori, draped clothing or futon over it and tucked their feet inside.
Two words, and they overlap
This is where the sources split, and it matters if you are reading a label. Wikipedia says the movable oki-gotatsu, “placed kotatsu”, came later, when tatami matting became common, and charcoal went into an earthen pot on the mat. In the same article’s list of types, though, “oki-gotatsu” names the modern electric table, and hori-gotatsu names the traditional table over a recessed floor, a pit about 40 centimetres deep.
JeePe uses the words in a third way. It says the Edo period made a portable oki-gotatsu popular, using a hibachi, a charcoal brazier, as the heat source, and it lists three types by shape: oki-gotatsu on the floor, hori-gotatsu with a lowered floor so legs can hang down, and a furniture-style kotatsu that works as an ordinary table once the futon is removed. We keep the two descriptions side by side. Our reading: oki means placed and hori means dug, and the rest is detail.
The electric turn
Wikipedia says that in the middle of the twentieth century, electricity replaced charcoal, and a heater could be fixed straight to the frame. It gives a figure for 1997: 81 per cent of Japanese homes had a kotatsu. JeePe is more specific about the date of the change, saying that in 1957 Tokyo Shibaura Electric, now Toshiba, made an electric yagura kotatsu and the device spread quickly as a household heater.
JeePe also tells a story it labels “said”: that a sunken kotatsu, letting a user dangle their legs, was built at the home of the British potter Bernard Leach in the Meiji period, because he found the formal kneeling posture, seiza, hard. We found it on that one page only.
Why it works
The explanation Wikipedia gives is about clothes and housing. The kotatsu was designed when people mostly wore traditional dress, so heat rose through the robes and warmed the body. Most Japanese housing, it says, is not insulated to Western standards and has no central heating, so a kotatsu is a cheaper way to stay warm, and families may gather in one area to save energy. The futon traps the warm air. In summer the blanket comes off and the table is used as a normal table.
What goes on top
Wikipedia lists the layers. A first blanket, the shitagake, goes over the frame and heater. A second, heavier cover, the kotatsu-gake, goes over that, under the tabletop. Historically the kotatsu-gake was made of bast fibres, and later of cotton, often indigo-dyed and pieced from old garments in the boro style. In the 2010s, the article says, covers were often decorative.
JeePe names three kinds of heater: quartz tube, halogen and carbon. It describes the quartz type as the classic, warming gradually, and the halogen as quick to warm.
The mikan and the family
Wikipedia says that in winter the kotatsu is often the centre of domestic life, with family members gathering to eat, watch television, play games and talk. JeePe adds the pairing of the kotatsu with mikan, Japanese mandarin oranges, calling it a famous winter combination. Its explanation, offered as its own, is that winter mikan keep well at room temperature and are easy to peel while chatting.
Sleeping under one
Both sources say not to do it overnight. Wikipedia says napping is generally considered acceptable but overnight sleep is not, because the body is not completely covered, the heating is uneven, and the low table makes accidental contact with heating elements possible, with a risk of burns. JeePe warns of low-temperature burns and dehydration, and says there is a long-standing saying that you will catch a cold if you sleep in a kotatsu. It cites Consumer Affairs Agency materials noting that even 44 degrees Celsius can cause burns after three to four hours. We pass on that figure as JeePe states it and have not read the agency’s own page.
JeePe’s etiquette notes are practical. Take off your shoes. Slide your legs in quietly rather than lifting the futon high. Keep skin from touching the heater. Do not put drinks where they could spill into the heater, since liquid inside can damage it or cause an electric shock.
Where a visitor can meet one
JeePe lists ryokan and minshuku with Japanese-style rooms, cafes in renovated old farmhouses, restaurants that put out kotatsu seating in winter, and the Sanriku Railway in Iwate Prefecture, which it says runs “kotatsu trains” in some winters. Rules vary by venue, it says, so follow the signs and the staff.
Similar tables elsewhere
Wikipedia names a Spanish equivalent, the mesa camilla, a small round table with a brasero underneath, and mentions the Iranian korsi. It calls them similar devices, not copies.
Dates in order
- Fourteenth century, Muromachi period: hearth platform and quilt, the hori-gotatsu ancestor, according to Wikipedia.
- Seventeenth century, Edo period: dug-out square around the irori, according to Wikipedia; portable hibachi kotatsu popular, according to JeePe.
- 1957: Toshiba electric yagura kotatsu, according to JeePe.
- Mid-twentieth century: electricity replaces charcoal, according to Wikipedia.
- 1997: 81 per cent of homes have a kotatsu, according to Wikipedia.
What kind of sources these are
Wikipedia, an open encyclopaedia, and JeePe, a travel and lifestyle site that carries affiliate advertising and says it does not guarantee accuracy. Neither cites a museum or a manufacturer. Treat the dates as outline, not detail.
What we left out
Electricity cost, wattage, brands and models, which vary and would date quickly. We also left out the other countries Wikipedia lists, and the Wikipedia remark that children catch cold under a kotatsu, which is marked “citation needed” there. We give JeePe’s version of that saying, as a saying.
Quick answers
When did the kotatsu begin?
According to Wikipedia, its history starts in the Muromachi period, in the fourteenth century, growing out of the irori hearth with a platform and a quilt.
Is it safe to sleep under a kotatsu?
Both Wikipedia and JeePe advise against sleeping overnight. Wikipedia cites uneven heating and the risk of burns from touching heating elements. JeePe adds dehydration.
What are the layers of a kotatsu?
Wikipedia lists a frame with a heater underneath, a first blanket called the shitagake, a heavier cover called the kotatsu-gake, and a tabletop on top.
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