1. The Recipe for Ohaguro: Iron Liquid (Kanemizu) and Insect Gall Powder (Fushi-ko)
The materials for ohaguro (blackened teeth) were two things: iron liquid, called kanemizu, and powder from insect galls, called fushi-ko. The iron liquid was made by fermenting rice washing water, vinegar, tea, sake, and old iron. It is reported to have had a very strong bad smell.[1]
The powder came from drying and grinding insect galls formed on the nurude tree.[1] According to dictionary descriptions, the application method involved brushing a liquid made by soaking old iron scraps in tea juice or vinegar onto the teeth. After that, the gall powder was applied.[2]
So, applying it required two steps: first the liquid, then the powder. But why do these two become black when they meet on the teeth?
2. Why Iron and Tannin Make Teeth Turn Black
The identity of the color is explained as a reaction between iron and tannin. The ferrous acetate in the iron liquid combines with the tannic acid in the galls. When they bind, the substance becomes hard to dissolve in water and turns black at the same time.[3]
It is also introduced that when iron salts are added to tannin, a stable black compound called iron tannate forms.[4]
This means the iron in the liquid and the tannin in the powder were kept separate until they met on the teeth. This is why layering them was necessary. Because the resulting black color does not dissolve easily in water, it likely did not wash away quickly after application.
3. How Married Women in the Edo Period Began Blackening Their Teeth
In the Edo period, women painted their teeth black upon marriage. The first ritual was called kanetsuke hajime. A female relative would become the kane-oya (iron parent), gift the full set of tools as a celebration, and teach how to apply it.[1]
Starting this smelly, time-consuming makeup alone is difficult. Having a senior person who teaches the steps along with the tools made this ritual a way to pass on life skills, in addition to being a celebration.
Regarding the meaning of black teeth, an explanation from the National Diet Library states that black was thought to be proof of chastity because it does not mix with other colors. However, using the phrase "thought to be," this is not confirmed as what everyone at the time believed.[1]
But was ohaguro only for married women?
4. How Ohaguro Spread from Heian Women to Samurai Men
Ohaguro is said to have been a habit of women until the end of the Heian period, when it spread to men as well.[5] The word tetsuzume (iron stain) first appears in the mid-Heian text Eiga Monogatari, and is also seen in The Tale of Genji and The Pillow Book.[5]
From the end of the Heian period, it spread to men. In the era of the Minamoto and Taira clans, some men are said to have blackened their teeth.[5] In the medieval period, it became common among upper-class samurai.[5]
However, by the Edo period, the habit for men had almost died out, remaining only as a mark of married women.[5] Even though the teeth were black, who blackened their teeth and what it meant changed with each era.
The origin is thought to be older. One theory suggests it goes back to the Kofun period because traces of ohaguro are seen on human bones and clay figures from burial mounds.[3] However, this material does not show definite dates based on excavation reports.
The custom is not unique to Japan. At the Dong Son archaeological site in Vietnam (about 2000 years ago), iron and sulfur were found in teeth from bones, and it is discussed that they may have been dyed with iron and tannin.[4]
5. Did Ohaguro Harm Teeth or Protect Them?
Both good and bad aspects of ohaguro are discussed. First, the bad side: the base liquid called kaneshita is a strong acid, and it seems it damaged the surface of the teeth.[1]
On the good side, today it is thought that the ingredients tightened the gums and strengthened tooth enamel, which may have helped prevent gum disease and cavities.[1] There is also a view that the black coating prevented cavities by covering the teeth.[3]
Note the phrase "is thought." No research in these materials proves that ohaguro reduced cavities. It is important to distinguish between "likely" and "proven."
When did this habit end?
6. Ohaguro After Japan Banned It in the Meiji Era
In the Meiji era, the situation changed. In 1870 (Meiji 3), tooth dyeing was banned for nobility. In 1873 (Meiji 6), it was announced that the Empress Dowager and Empress stopped using ohaguro and eyebrow makeup.[7][5]
The background is said to be that it looked strange to Westerners and a push to Westernize customs.[5] However, the ban applied only to upper classes like nobility, not all common people.
In fact, it remained strongly among common people. Even in the mid-Meiji era, "easy ohaguro" powders that could be used just by dissolving them in water were sold.[7] Woodblock prints from around 1877 (Meiji 10) also show women with black teeth.
When it disappeared varies by source. Some dictionaries say it continued mainly until the end of the Meiji era in common society, and into the early Showa era in some regions like Tohoku. Other explanations say it vanished earlier.[3] The end date cannot be pinned to one time.
7. How We Can Learn About Ohaguro Today from Pictures and Old Words
Ohaguro is a habit we cannot see today. Still, clues can be found in several ways.
One way is looking at pictures. In Edo and Meiji woodblock prints, look at the color of the teeth shown in women's prints. Chapters 1 and 2 of the National Diet Library explanation include images and are readable.[1][7]
Another way is old words. Reading modern translations to find where tetsuzume appears in The Tale of Genji or The Pillow Book can be fun.
Research on ohaguro continues today. Studies of dental tartar from human remains are exploring the relationship between ohaguro and tooth disease.[6]