Have you ever seen a hot spring tinted brown, resembling the color of tea? This unique color is due to the oxidation of iron. Many iron-rich springs exhibit this brown tint.

What Are Brown-Tinted Hot Springs?

Brown-tinted hot springs refer to iron-rich springs that have oxidized upon exposure to air, turning from reddish-brown to yellowish-brown.

The intensity of the color varies depending on the concentration of iron. It ranges from light yellow to deep reddish-brown, offering various shades.

Why Do They Turn Brown?

The mechanism behind the formation of brown-tinted hot springs is simple.

Freshly emerged iron-rich springs from underground are transparent because the iron ions are dissolved in the water.

However, once exposed to air, the iron ions oxidize. The oxidized iron becomes iron rust. This iron rust is the true identity of the brown tint.

In other words, brown-tinted hot springs are evidence of "fresh iron-rich springs."

Witnessing the Color Change

One fascinating aspect of iron-rich springs is the ability to witness the color change process.

At the source, clear water flows. Once it comes into contact with air, it gradually turns yellowish and eventually changes to brown.

Some facilities allow you to observe this color change process. A chemical reaction occurs right before your eyes, allowing you to experience a "living hot spring."

Types of Brown-Tinted Hot Springs

While brown-tinted hot springs are primarily iron-rich springs, they can be further categorized based on the type of iron ions.

Iron(II)-Bicarbonate Springs: The most common type of iron-rich spring, known for its brown tint.

Iron(II)-Sulfate Springs: A combination of sulfate and iron, also resulting in a brown tint.

Additionally, hot springs containing iron, even if not classified as iron-rich springs, can also exhibit a brown tint.

Notable Brown-Tinted Hot Springs

Arima Onsen's Kinsen (Hyogo Prefecture): One of Japan's three famous hot springs, known for its reddish-brown "Kinsen" rich in iron and salt.

Naruko Onsen (Miyagi Prefecture): A hot spring area offering diverse spring qualities, including brown-tinted iron-rich springs.

Kawayu Onsen (Wakayama Prefecture): Digging into the riverbed reveals hot springs. Contains iron, resulting in a brown tint.

Benefits of Brown-Tinted Hot Springs

Brown-tinted hot springs (iron-rich springs) are rich in iron.

While iron absorption through bathing is limited, drinking the spring water allows iron intake into the body, believed to help improve anemia.

Additionally, they promote blood circulation, warming the body from the core and aiding in the improvement of cold sensitivity.

Precautions When Bathing

When entering brown-tinted hot springs, there are several precautions to consider.

Towels May Stain: Iron rust may adhere, causing towels to turn brown. Use facility-provided towels or bring old towels.

Avoid White Clothing: After bathing, wearing white clothes may result in iron rust stains. Choose darker clothing.

Iron Rust on Bathtubs: Although facilities clean regularly, iron rust may be present on bathtubs and washbasins. This is evidence of "genuine iron-rich springs."

Enjoying Brown-Tinted Hot Springs

Brown-tinted hot springs are visually enjoyable.

Immerse yourself in water with a tea-like color. Enjoy the unique hues and feel the richness of iron.

Observing the process of the source water changing from transparent to brown is also intriguing. It's a rare experience to witness a chemical reaction in real-time.

In facilities where drinking the spring water is allowed, you can taste the iron. It has a metallic taste, which is the "taste of iron."

Conclusion

Brown-tinted hot springs are iron-rich springs that have oxidized. Their unique tea-like color is captivating.

Initially transparent, they turn brown upon exposure to air. Observing this color change process is part of the charm of iron-rich springs.

Drinking the spring water is believed to help improve anemia. While towels may stain, this is part of the enjoyment of "genuine iron-rich springs." If you find a brown-tinted hot spring, be sure to experience it.