What type of hot spring is Kusatsuonsen Bouun?

Kusatsuonsen Bouun is classified as "酸性水素・硫酸塩・塩化物温泉（低張性酸性高温泉）" (酸性泉, 塩化物泉, 硫酸塩泉 spring type).

What is the pH of Kusatsuonsen Bouun?

Kusatsuonsen Bouun (Bandaiko) has a pH of 1.75. It is strongly acidic with high antimicrobial properties.

Does Kusatsuonsen Bouun have beauty benefits for skin?

Yes. Kusatsuonsen Bouun contains 528.3mg/kg of metasilicic acid, exceeding the 50mg/kg beauty spring standard. It helps improve skin texture and moisture retention.

Is Kusatsuonsen Bouun a natural flow hot spring?

Kusatsuonsen Bouun is a natural flow spring, unheated, undiluted, non-recycled.

Image: Agoda

PR · Agoda

Kusatsuonsen Bouun

望雲

Verified

Gunma Kusatsu

群馬県草津町

Onsen RyokanFree-Flowing Onsen

AT A GLANCE

Kusatsuonsen Bouun is an acidic spring, chloride spring, and sulfate spring (pH 1.8, strongly acidic). Naturally flowing (no recycling or dilution). Contains ≥50 mg/kg of metasilicic acid, certified as a beauty spring. Per Japan's Ministry of the Environment guidelines, indicated for atopic dermatitis and psoriasis.

SOURCES

♨Bandaiko

万代鉱

Acidic hydrogen sulfate chloride spring (hypotonic acidic high-temperature spring)

Sulphate SpringpH 1.7594.6℃Self-flowi…

See effects, components & details

♨Nishinokawara Gensen

Sulphate SpringpH 253.7℃自然湧出

See effects, components & details

If a source spring listed for this facility looks incorrect, please contact us.

How Long to Stay (Toji)

Start with 2 nights / 3 days

Japan’s Ministry of the Environment notes that even a short stay refreshes you. For a full therapeutic cure, around 2–3 weeks is the guideline.

Kusatsuonsen Bouun

From¥18,700/ person / night (tax incl.)

4.7(1390)

Approx. lowest rate (varies by date & guests)

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Sample caption

Kusatsuonsen Bouun (Kusatsu) Acidic Spring / Chloride Spring / pH 1.75 / 94.6℃ #onsen #kusatsu #acidicspring https://onsen-analysis.com/en/onsen/kusatsuonsen-bouun?utm_source=card&utm_medium=social&utm_campaign=onsen_card

USAGE

Free-Flowing Onsen

Pure spring water — no dilution, no recirculation

HeatedNo

DilutedNo

RecycledNo

FilteredNo

DisinfectedNo

AdditivesNo

▸Note

The temperature, pH and component values shown here are based on the hot spring analysis (source). Actual values in the bath may differ depending on heating, dilution, recycling and filtration. Please check current usage status at the facility.

Famous Onsen Area

Kusatsu Onsen — overview, spring types, and access

酸性泉

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Learn more

Acidic Spring — benefits, bathing tips, and onsen-hopping order

By health concern

Conditions this spring type may help with

Cold Sensitivity Skin Beauty and Dry Skin Atopic Dermatitis Psoriasis Cutaneous Pyogenic Infection Wound Healing

ACCESS

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✨ The descriptions, catch phrases, and translations on this page are generated by AI (Claude). pH, temperature, and component values are OCR-extracted from the official analysis report. Learn more