Why Japan's Court Ladies Washed Their Floor-Length Hair in Rice Water

Why Japan's Court Ladies Washed Their Floor-Length Hair in Rice Water
Heian court women and their long, loose hair, in the “Azumaya” scene of the illustrated Tale of Genji handscroll, about 1130.

A thousand years ago, cloudy water sat in a silver bowl in a Kyoto palace. A century ago, a chemist in London gave the protein in that grain a name. Today it ends up on a strand of hair.

In the Seiryōden, the emperor's residence in the old palace at Kyoto, there is a small silver bowl with a name almost nobody uses anymore: the yusurutsuki. It held yusuru, the milky water left over after rice was rinsed.

The court ladies of the Heian period wore their hair long. It wasn't shoulder length or waist length. It reached the floor and trailed behind them across the tatami, in a style called suberakashi. According to the old accounts, they combed that hair every day with the rinse water from the rice.

Water like that looks like nothing. It's the color of weak milk and has a faint sweet smell. It's poured away in most kitchens without a second look.


Yusuru: the cloudy water left after rinsing rice.

In 2010, a team of researchers at the Japanese company Kracie decided to look at it properly. They treated hair with yusuru and measured what happened. The surface of the strand got less rough, so a comb dragged less. The fibre also got more elastic. Then they found a catch: used on its own, the rice water left flakes behind. The researchers went looking for the parts of the water that did the work without the mess.

One of them was a sugar called inositol. Using an infrared microscope at the SPring-8 synchrotron, Kracie reported that inositol soaked into the strand and was still there after rinsing.

That is the first half of the story: a palace habit, a bowl, and a modern lab checking what an old ritual was doing. The second half is smaller, and stranger.

Inside the grain

Under a microscope, a cut grain of rice isn't solid white. The pale inner part, the endosperm, is packed with starch, and scattered through the starch are tiny storage parcels of protein called protein bodies. The plant builds them while the grain fills, starting around five days after the rice flowers.

Most of what's inside those parcels is a protein called oryzenin.

It got its name in the early 1900s. In 1912 the Biochemical Journal published "The Proteins of Rice" by S. Kajiura, written in the physiology laboratory at King's College London. The paper described rice's main protein as a glutelin, a kind that dissolves in dilute alkali instead of water or alcohol.

That made rice unusual. In most cereals, the main stored protein is split between glutelins and prolamins. Wheat's gluten, for example, is partly prolamin. In rice, glutelin dominates. A 1982 study in Plant Physiology put it at 80% or more of the protein in the endosperm, with prolamin under 5%.

The grain doesn't even make oryzenin in one piece. It first builds a single long chain, then cuts it into two smaller subunits that fold together and settle into the protein bodies. Researchers call these bodies PB-II. They come from the cell's storage vacuoles and hold most of the rice's stored protein.

So the plant is already doing what a formulator does: building a protein, trimming it, and packing it away for later.

From grain to strand

To get rice protein into hair care, the protein is broken into shorter pieces. This is hydrolysis, which leaves short chains of amino acids called peptides. Yes natural peptides exist! The size of the pieces matters.

Hair is wrapped in a cuticle, overlapping flat cells laid like roof shingles. Research on protein conditioners finds that the smallest peptides can work their way between those shingles. Larger ones tend to stay on the outside, where they leave a thin film along the strand. Ingredient suppliers describe low-molecular-weight rice peptides as clinging well to the cuticle.

That film is the whole point, and it's modest. The film coats the strand. It smooths the surface so the comb snags less, and a strand that snags less breaks less. The hair isn't growing; there's simply less of it on the brush and more of it left on the head, so it looks fuller.

Where Flint & Stone comes in

Flint & Stone is two bars, a shampoo bar with 8 ingredients and a conditioner bar with 14, and rice protein is in both of them.

It's the protein from the grain, used for the same quiet job the comb found a thousand years ago: coating each strand so it feels stronger, breaks less when it's brushed, and looks fuller.

Hair washed with a bar a few times a week still has all the same old habits: a comb, some patience, some care. The protein simply goes along for the wash. 

Check them out here

Sources

Image credits

  • Top image: Genji Monogatari Emaki, “Azumaya” (c. 1130), Tokugawa Art Museum, Nagoya. Painters of the Heian court. License: Public domain. Source: Wikimedia Commons.
  • Second image: Flint & Stone.
  • Third image: Flint & Stone shampoo bar and conditioner bar.
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