Bandaiko
Analysis UnverifiedThe Mandaiko source, originating from traces of past mining development, is deeply intertwined with Kusatsu Onsen's unique yumomi culture and its long history of toji (therapeutic bathing). Its highly acidic waters, among Japan's most potent, deliver a distinctive tingling sensation, awakening both mind and body and offering a sense of rejuvenation. The high-temperature blessings penetrate deep into the core, leaving you with a surprisingly light and refreshed feeling after your bath. We invite those seeking a genuine toji experience, a true escape from daily life to restore their mind and body, to discover the profound power of this spring.
The bar length shows how abundant each component is compared to thresholds that make it "distinctive" (therapeutic spring standards, beauty spring criteria, etc.).
Strong astringent action that tightens skin. A key component of acidic springs, suited to oily or acne-prone skin.
Mild antibacterial action keeps the skin clean. Trace transdermal absorption supports tooth and bone health.
A natural moisturizer also used in skincare lotions. Forms a thin veil on the skin to reduce moisture loss after bathing.
A trace component with gentle antibacterial and anti-inflammatory action.
- Acidic (pH)pH 1.75
- Feel
- May tingle on the skin; tastes sour.
- Said to
- Said to be strongly antibacterial. Bathing indications include atopic dermatitis and plaque psoriasis.
- Note
- Can irritate sensitive skin—rinse with fresh water after bathing. Keep it out of your eyes.
- Chloride (salt)708 mg/kg
- Feel
- Tastes salty; the warmth lasts after you get out.
- Said to
- Salt is said to form a film on the skin that keeps in heat and moisture. Bathing indications include cuts, poor circulation and dry skin.
- Note
- May sting cuts. Strong salty water can tire you—avoid long soaks.
- Sulfate840 mg/kg
- Feel
- Your skin feels moist; the water may taste slightly bitter.
- Said to
- Said to retain heat well and help heal cuts. Bathing indications include cuts and dry skin.
- Note
- It warms you well—do not stay in too long.
- Metasilicic acid528 mg/kg
- Feel
- Your skin may feel smoother.
- Said to
- 50 mg/kg or more is said to mark a “skin-beautifying spring”; it is also used in skincare.
- Note
- The “skin-beautifying” label is a common rule of thumb, not a legal standard.
- Source temperature94.6℃
- Feel
- The source is 42°C or hotter; the bath may be on the hot side.
- Said to
- Heat is said to boost circulation and warm the body.
- Note
- Older people and those with high blood pressure or heart conditions should avoid baths of 42°C or more. Keep soaks short.
Effects are general descriptions based on the Ministry of the Environment’s indications by spring type, not a guarantee.
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.
▸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.
Given the extremely low pH of 1.75, start with short sessions of 3–5 minutes and monitor your skin's reaction before gradually extending to 10–15 minutes. After bathing, pat dry with a towel rather than rinsing—though those with sensitive skin are advised to rinse off with warm water. Limit bathing to once or twice daily at first, and only increase frequency after the third day to avoid 'yu-atari' (thermal fatigue), following the classic Kusatsu bathing tradition.
Bandaiko spring boasts one of Japan's most intensely acidic profiles—pH 1.75 at 94.6°C—with dissolved solids totaling 3.18 g/kg, dominated by sulfate (840 mg/kg) and chloride (707 mg/kg). Its powerful bactericidal action has earned recognition for atopic dermatitis, psoriasis, and pyoderma, while also being indicated for peripheral circulatory disorders, chills, and depressive states. It is especially recommended for those with chronic joint or muscle pain and those seeking to fundamentally restore skin health.
Those with sensitive skin or mucous membranes, and elderly individuals with dry skin conditions should avoid this spring due to its spring-specific contraindications. People with serious heart, lung, or kidney disease, active bleeding, or illness in the acute phase should also refrain from bathing.
※ See the analysis data below for detailed contraindications
ANALYSIS DATAView all analysis fields ▼
Source Info
- Source name
- Bandaiko
- Spring type
- Acidic hydrogen sulfate chloride spring (hypotonic acidic high-temperature spring)
- Source temperature
- 94.6℃
- pH
- 1.75
- Flow type
- Self-flowing from drilling
- Osmotic pressure
- Hypotonic
Analysis Document
- Analysis date
- 2023-08-04
- 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
- Lead ion Pb²⁺
- 0.08 mg/kg
- Copper ion Cu²⁺
- 0.00 mg/kg
- Total cations
- 463 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
- 2142 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
- 578 mg/kg
Dissolved Gas
- Free carbon dioxide CO₂
- 26.4 mg/kg
- Free hydrogen sulfide H₂S
- 0.00 mg/kg
- Total dissolved gas
- 26.4 mg/kg
Totals
- Total dissolved substances
- 3180 mg/kg
- Component total
- 3210 mg/kg
- Evaporation residue
- 2520 mg/kg
Usage
- Heating
- No
- Dilution
- Yes（Water dilution for temperature adjustment. As the source spring temperature is extremely high at 94.5-96°C, water dilution is performed to lower the temperature to levels suitable for drinking. While some facilities specify "no water dilution or heating" on official websites, water dilution is typically included during heat exchange in the distribution system.）
- 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
