Bandaiko

Analysis Verified
万代鉱
The Strongest Spring from the Mine

The Bandaiko source, which unexpectedly erupted from within the Bandai Sulfur Mine in 1970, now stands as Kusatsu's primary hot spring, boasting the largest output and supporting the town. Named with the wish for 'eternal prosperity' (万代), this powerful source was born in the mountains, far from the Yubatake (Kusatsu's central hot-water field). Its colorless, transparent waters deliver a stimulating tingle that awakens both mind and body, while its robust warmth permeates to the very core. This energetic spring is a perfect companion for those seeking liberation from daily routines and a crisp mental and physical rejuvenation.

AI Generated
This source matches 3 spring types· Tap to switch
SPRING TYPE
Acidic Spring

These springs have a strong antibacterial effect which can result in a mild tingling sensation on contact. Effective for healing wounds and relieving inflammatory skin conditions. Those with sensitive skin should rinse with fresh water after bathing.

See features & indications
Bathing indications
Atopic dermatitisPlaque psoriasisEpidermal suppurationImpaired glucose tolerance (diabetes)
Cautions
  • 皮膚または粘膜の敏感な方、高齢者の皮膚乾燥症の方は禁忌です。
  • 肌が弱い方は入浴後に真湯で洗い流してください。
Definition :Contains 1 mg/kg or more of hydrogen ions.
Source: 環境省「あんしん・あんぜんな温泉利用のいろは」(監修:日本温泉気候物理医学会)Read full article
PH VALUE
1.7
Strongly Acidic
Acidic ← 07 Neutral14 → Alkaline
Strongest class of acidic springs. Very strong antibacterial and skin-softening effects. Kusatsu Onsen (pH 1-2) is a representative example.
Caution: Avoid prolonged bathing. Rinse with fresh water or weakly alkaline water after bathing. Those with sensitive skin or mucous membranes should refrain from bathing.
TEMPERATURE
94.6
Very Hot Spring
Near boiling, extremely hot. Requires substantial cooling or dilution.
KEY MINERALS

The bar length shows how abundant each component is compared to thresholds that make it "distinctive" (therapeutic spring standards, beauty spring criteria, etc.).

Aluminum ionSee detail
43.2 mg/kg

Strong astringent action that tightens skin. A key component of acidic springs, suited to oily or acne-prone skin.

Fluoride ionSee detail
25.1 mg/kg

Mild antibacterial action keeps the skin clean. Trace transdermal absorption supports tooth and bone health.

Metasilicic acidSee detail
528 mg/kg

A natural moisturizer also used in skincare lotions. Forms a thin veil on the skin to reduce moisture loss after bathing.

Metaboric acidSee detail
21.4 mg/kg

A trace component with gentle antibacterial and anti-inflammatory action.

Bromide ionSee detail
4.5 mg/kg

Gentle calming action; often found alongside chloride.

CHARACTER · COMPOSITION PROFILE
1234StimulationBactericidalSkin BeautyHeat RetentionRelaxation

Scores are calculated from mineral analysis data based on the Mineral Spring Analysis Guidelines (Ministry of Environment, Japan). They are unrelated to facility atmosphere or service quality.

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.

SENSORY TEST
Color
無色透明
Smell
僅かに硫化水素臭
EFFECTS
Spring-specific indications (bathing)
Atopic dermatitisPlaque psoriasisEpidermal suppurationImpaired glucose tolerance (diabetes)Cuts and grazesPeripheral circulatory failurePoor circulationDepressionXeroderma
General indications (bathing)
High blood pressure (mild)Rheumatoid arthritisAutonomic instabilityInsomniaChronic pain or stiffness in muscles and jointsMuscle stiffness due to motor paralysisGastrointestinal dysfunction
Contraindications
Acute illness (especially with fever)Active tuberculosisMalignant tumorsSevere heart diseaseRespiratory failureRenal failureBleeding disordersSevere anemiaAny actively progressing illnessPregnancy (especially early and late stages)Sensitive skin or mucous membranes, eye conditions (acidic springs)
BATHING TIPS
AI Generated

With a very high acidity of pH 1.7, this stimulating water may cause a tingling sensation. It can sting sensitive skin or open cuts. Avoid long soaks and start with shorter dips. It's recommended to rinse off with fresh water after bathing.

EFFECT STORY
AI Generated

The defining features of Bandaiko are its high temperature of 94.6°C and its powerful acidity of pH 1.7. This potent acid spring is expected to be effective for skin conditions like atopic dermatitis and psoriasis, as well as for diabetes (impaired glucose tolerance).

CAUTIONS
AI Generated

Due to its strong acidity, caution is advised for those with sensitive skin or mucous membranes, and for elderly individuals with dry skin. Avoid bathing during active illness or when feeling weak.

※ See the analysis data below for detailed contraindications

ANALYSIS DATAView all analysis fields ▼

Source Info

Source name
Bandaiko
Spring type
酸性水素一硫酸塩・塩化物温泉
Old spring type name
酸性明礬泉
Source temperature
94.6℃
pH
1.7
Flow type
掘削自噴
Osmotic pressure
低張性

Analysis Document

Analysis date
2023-07-25
Analyst organization
一般社団法人 群馬県薬剤師会(環境衛生試験センター)
Registration No.
群馬薬第2号

Cations

Hydrogen ion H⁺
19.9 mg/kg
Sodium ion Na⁺
138 mg/kg
Potassium ion K⁺
64.4 mg/kg
Ammonium ion NH₄⁺
0.40 mg/kg
Magnesium ion Mg²⁺
76.0 mg/kg
Calcium ion Ca²⁺
114 mg/kg
Aluminum ion Al³⁺
43.2 mg/kg
Manganese ion Mn²⁺
3.6 mg/kg
Iron(II) ion Fe²⁺
3.0 mg/kg
Copper ion Cu²⁺
0.00 mg/kg
Total cations
0.46 mg/kg

Anions

Fluoride ion F⁻
25.1 mg/kg
Chloride ion Cl⁻
708 mg/kg
Sulfate ion SO₄²⁻
840 mg/kg
Bromide ion Br⁻
4.5 mg/kg
Hydrogen sulfate HSO₄⁻
565 mg/kg
Total anions
2.1 mg/kg

Undissociated Components

Sulfuric acid H₂SO₄
28.5 mg/kg
Metasilicic acid H₂SiO₃
528 mg/kg
Metaboric acid HBO₂
21.4 mg/kg
Total undissociated
0.58 mg/kg

Dissolved Gas

Free carbon dioxide CO₂
26.4 mg/kg
Free hydrogen sulfide H₂S
0.00 mg/kg
Total dissolved gas
0.03 mg/kg

Totals

Total dissolved substances
3.2 mg/kg
Component total
3.2 mg/kg
Evaporation residue
2.5 mg/kg

Usage

Heating
No
Dilution
No
Recycle / Filter
No
Additives
No
Disinfection
No

Indications & Contraindications

Bathing indications
Atopic dermatitis, Plaque psoriasis, Epidermal suppuration, Impaired glucose tolerance (diabetes), Cuts and grazes, Peripheral circulatory failure, Poor circulation, Depression, Xeroderma
General indications
High blood pressure (mild), Rheumatoid arthritis, Autonomic instability, Insomnia, Chronic pain or stiffness in muscles and joints, Muscle stiffness due to motor paralysis, Gastrointestinal dysfunction
Contraindications
Acute illness (especially with fever), Active tuberculosis, Malignant tumors, Severe heart disease, Respiratory failure, Renal failure, Bleeding disorders, Severe anemia, Any actively progressing illness, Pregnancy (especially early and late stages), Sensitive skin or mucous membranes, eye conditions (acidic springs)

Drinking

Drinkability
Not drinkable
FACILITY INFO
AI draft (unverified)
Official site
Tattoo
No tattoosGuests with tattoos (irezumi) are kindly requested to refrain from using the public baths and open-air baths.
About tattoos and onsen
Hours
Weekdays: 15:0010:00
Weekends & holidays: 15:0010:00
The men's and women's baths switch daily at 3:00 PM and 5:00 AM. The baths are closed during the day for cleaning and at night for security and accident prevention.
Transit
From JR Agatsuma Line (JR吾妻線) 'Naganohara-Kusatsuguchi Station' (長野原草津口駅), take a local bus for approx. 25 minutes to 'Kusatsu Onsen Bus Terminal' (草津温泉バスターミナル). From the bus terminal, it's about a 3-5 minute walk. Alternatively, shuttle service is available from the bus terminal (reservation required). From Busta Shinjuku (バスタ新宿), take the highway bus 'Joshu Yumeguri-go' (上州ゆめぐり号) to Kusatsu Onsen Bus Terminal (草津温泉バスターミナル) (approx. 247 minutes), then about a 3-minute walk.
Parking
Available. 500 JPY per night per vehicle. Capacity: 100 vehicles. Available hours: 12:00 PM (noon) to 12:00 PM (noon) the next day. Not available for day-use guests. Height limit: 2.8m.
Facilities
RestaurantLoungeBanquet HallPublic BathOpen-air BathShopVending MachineEV Charging Station
House rules
All rooms are non-smoking (smoking areas are located on the 3rd floor front lobby of the main building and the 2nd floor elevator hall of the annex). The public baths and open-air baths operate on a gender-swapping schedule.
This information may change without notice. Please contact the facility directly for accurate details.
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.

More on toji length
Stay at this hotel
PR

Kusatsuonsen Ichii

From¥17,600/ person / night (tax incl.)
4.6(3162)

Approx. lowest rate (varies by date & guests)

Book on Rakuten Travel

Powered by Rakuten Travel

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