Actually, Japanese hot springs generally have two distinct "personalities": Acidic and Alkaline.
If you jump in without knowing the difference, your precious ring might turn black, or you might slip and fall on the floor. In this article, we provide the ultimate guide to choosing the perfect onsen for you from the scientific perspective of "pH."
1. Seek Stimulation with "Acidic Onsen"
~ A Samurai-like Intense Detox Experience ~
If you are looking for a "uniquely intense Japanese experience" or a serious "refresh," we recommend acidic hot springs with a low pH (below pH 3).
What kind of experience is it?
Acidic water often provides a tingling sensation on the skin. This is proof that the water possesses strong bactericidal power. Historically, Japanese people have used these "intense waters" to cure wounds and skin diseases. Additionally, the water has a "peeling effect" that dissolves old skin cells, forcibly resetting your skin.
Where to go?
- Kusatsu Onsen (Gunma): One of Japan's most famous acidic hot springs. You can see the traditional "Yubatake" (hot water field) scenery that looks like something out of the movie Thermae Romae. It is accessible by bus or train from Tokyo.
- Tamagawa Onsen (Akita): Boasting Japan's strongest acidity (pH 1.2), this is truly an extreme onsen experience.
⚠️ Points for Travelers to Note
- Remove Jewelry: Acidic water corrodes metal. If you enter wearing gold or silver necklaces or rings, they will turn black instantly. Be sure to leave them in a locker.
- Don't Forget Rinsing: If you have sensitive skin, please rinse the hot spring ingredients off your body with a fresh water shower before getting out of the bath. Leaving it on may cause skin roughness.
2. Relaxation and Beauty with "Alkaline Onsen"
~ Like Beauty Serum! A Silky Touch ~
If you are seeking "relaxation after skiing" or "silk-like skin," alkaline hot springs with a high pH (above pH 8.5) are best.
What kind of experience is it?
The moment you enter the water, you will be surprised that your skin feels "slippery." This is because a chemical reaction called "saponification"—the same reaction used to make soap—is occurring on your skin. It gently removes excess sebum and dirt, leaving your skin surprisingly smooth after the bath. In Japan, these are called "Beauty Baths."
Where to go?
- Hakuba Happo Onsen (Nagano): A high-alkaline hot spring (pH 11+) located in the world-class snow resort "HAKUBA." It is perfect for soothing muscle pain after skiing or hiking.
- Tokigawa Onsen (Saitama): A top-class strong alkaline spring in Japan that can be visited on a day trip from Tokyo.
⚠️ Points for Travelers to Note
- Watch Your Step: The alkaline ingredients make the floor extremely slippery. Please be especially careful when entering and exiting the bathtub.
- Moisturizing: Since sebum and dirt are thoroughly removed, your skin tends to dry out easily after the bath. Apply body lotion or cream immediately after bathing.
Summary: Which Do You Prefer?
- If you want a stimulating refresh experience → Go to Acidic Onsen (Take off your jewelry!)
- If you want a silky beautiful skin experience → Go to Alkaline Onsen (Watch your step!)
On your next trip to Japan, don't just soak in the water—try becoming an "Onsen Master" by feeling the difference in pH!
