Ubayu Gensen

Analysis Unverified
姥湯源泉
Cliffside Milky Acid Spring

Ubayu Gensen gushes naturally from fissures in acidic welded tuff at roughly 1,250 metres on the flank of Mount Dainichi in the Azuma range. Tradition holds that Endo Okura, a gold prospector, found it in 1533 after meeting a mountain crone — the yamauba whose name the source still carries. Carried down by gravity through vinyl piping and cooled in troughs that harvest sulphur flowers, its pH 2.6 waters bubble with hydrogen sulphide, tightening the skin and leaving a clean lightness behind. It suits travellers who want deep mountain stillness.

AI Generated
This source matches 4 spring types· Tap to switch
SPRING TYPE
Sulfur Spring

These springs have an aroma that recalls boiled-eggs and can be cloudy white, blue or green. They boast strong antibacterial qualities and can be effective at healing wounds and relieving inflammatory skin conditions while also promoting circulation.

See features & indications
Bathing indications
Atopic dermatitisPlaque psoriasisChronic eczemaEpidermal suppuration
Drinking indications
Impaired glucose tolerance (diabetes)Dyslipidemia (high cholesterol)

※ Only at facilities permitted to serve drinking water. 200–500 mL/day recommended.

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 2 mg/kg or more of total sulfur.
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
2.6
Acidic
Acidic ← 07 Neutral14 → Alkaline
Acidic spring (pH < 3). Antibacterial and skin-softening effects. Known for a refreshing bathing experience.
Caution: Avoid prolonged bathing. Rinse with fresh water after bathing. Not recommended for those with open wounds.
TEMPERATURE
51.0
Hot Spring
Quite hot. Often diluted with water for a comfortable bathing temperature.
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
30.9 mg/kg

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

Free hydrogen sulfideSee detail
4.5 mg/kg

The aroma typical of sulfur springs, with circulatory and antibacterial effects.

Iron(II) ionSee detail
22.2 mg/kg

An iron-rich spring whose water turns yellow-brown to red-brown when exposed to air. Strong heat retention.

Metaboric acidSee detail
5.6 mg/kg

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

Metasilicic acidSee detail
46.6 mg/kg

A natural moisturizer that leaves a hydrated feel on the skin.

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
白色微濁
Smell
硫化水素臭
Taste
収れん味及び鉄味
EFFECTS
Spring-specific indications (bathing)
Atopic dermatitisPlaque psoriasisChronic eczemaEpidermal suppurationImpaired glucose tolerance (diabetes)Autonomic instabilityInsomniaDepression
General indications (bathing)
High blood pressure (mild)Rheumatoid arthritisChronic 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)Severe chronic dermatitis (sulphur springs)Sensitive skin or mucous membranes, eye conditions (acidic springs)
BATHING TIPS
AI Generated

With a pH of 2.6 and a source temperature of 51.0°C, keep the first soak to three to five minutes and rest before returning. Bathers with sensitive skin or older guests should rinse with fresh water afterwards and drink plenty of fluids.

EFFECT STORY
AI Generated

Its pH 2.6 acidity and 4.5 mg/kg of free hydrogen sulphide have long made this a water for cleansing and settling the skin. Waters combining sulphur and acidity are traditionally associated with immune system stimulation, while 22.2 mg/kg of iron(II) may support rejuvenation. A good choice for days when silky skin is the goal.

CAUTIONS
AI Generated

Those with sensitive skin or mucous membranes, and older bathers with dry skin, fall under this spring's specific contraindications. Avoid bathing during active illness or severe anaemia.

※ See the analysis data below for detailed contraindications

ANALYSIS DATAView all analysis fields ▼

Source Info

Source name
Ubayu Gensen
Spring type
Acidic Sulfur-containing Iron(II) Simple Hot Spring
Source temperature
51℃
pH
2.6
Flow type
自然湧出
Osmotic pressure
低張性

Analysis Document

Analysis date
2014-10-23
Analyst organization
日本環境科学株式会社
Registration No.
温泉分析山形第2号

Cations

Hydrogen ion H⁺
3.2 mg/kg
Lithium ion Li⁺
< 0.1 mg/kg
Sodium ion Na⁺
27.1 mg/kg
Potassium ion K⁺
15.6 mg/kg
Magnesium ion Mg²⁺
6.3 mg/kg
Calcium ion Ca²⁺
44.1 mg/kg
Aluminum ion Al³⁺
30.9 mg/kg
Manganese ion Mn²⁺
0.50 mg/kg
Iron(II) ion Fe²⁺
22.2 mg/kg
Zinc ion Zn²⁺
0.04 mg/kg
Lead ion Pb²⁺
< 0.01 mg/kg
Copper ion Cu²⁺
< 0.01 mg/kg
Cadmium ion Cd²⁺
< 0.01 mg/kg
Total cations
0.15 mg/kg

Anions

Fluoride ion F⁻
1.1 mg/kg
Chloride ion Cl⁻
10.7 mg/kg
Sulfate ion SO₄²⁻
525 mg/kg
Bicarbonate ion HCO₃⁻
< 0.1 mg/kg
Carbonate ion CO₃²⁻
< 0.1 mg/kg
Bromide ion Br⁻
< 0.1 mg/kg
Iodide ion I⁻
< 0.1 mg/kg
Hydrogen sulfate HSO₄⁻
55.9 mg/kg
Total anions
0.59 mg/kg

Undissociated Components

Sulfuric acid H₂SO₄
0.40 mg/kg
Metasilicic acid H₂SiO₃
46.6 mg/kg
Metaboric acid HBO₂
5.6 mg/kg
Total undissociated
0.05 mg/kg

Dissolved Gas

Free carbon dioxide CO₂
< 0.1 mg/kg
Free hydrogen sulfide H₂S
4.5 mg/kg
Total dissolved gas
0.00 mg/kg

Totals

Total dissolved substances
0.79 mg/kg
Component total
0.80 mg/kg
Evaporation residue
0.76 mg/kg

Usage

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

Indications & Contraindications

Bathing indications
Atopic dermatitis, Plaque psoriasis, Chronic eczema, Epidermal suppuration, Impaired glucose tolerance (diabetes), Autonomic instability, Insomnia, Depression
General indications
High blood pressure (mild), Rheumatoid arthritis, 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), Severe chronic dermatitis (sulphur springs), Sensitive skin or mucous membranes, eye conditions (acidic springs)

Drinking

Drinkability
Not drinkable
FACILITY INFO
AI draft (unverified)
Official site
Tattoo
Confirming
Bathing wear (Yuami-gi)
Not available
About tattoos and onsen
Hours
Weekdays: 09:3015:30
Weekends & holidays: 09:3015:30
Day-use bath reception hours. Outdoor baths only available.
Closed days: Irregular holidays (for day-use baths), Early November - Late April (winter closure).
Transit
Get off at JR Ou Main Line Toge Station (JR奥羽本線峠駅). Shuttle service available for staying guests only (reservation required). Approx. 25 min from Toge Station to parking, then approx. 200-250m walk from parking to inn. If walking, approx. 8km (2h 20min) from Toge Station. By car: Approx. 70 min from Tohoku Expressway Fukushima-Iizaka IC (東北自動車道福島飯坂IC) via National Route 13 (国道13号線), or approx. 1h 10min from Yonezawa-Chuo IC (米沢中央IC).
Parking
Free parking available (40 spaces). Approx. 200-250m walk from parking to inn (approx. 5 min). Cars cannot be parked directly in front of the entrance.
Day use fee
¥700Children (ages 3 to elementary school age) 300 yen. Outdoor baths only available.
Facilities
Outdoor baths (mixed-gender & women-only)Indoor baths (gender-separated)Toilets with bidet functionsShampooConditionerBody soapHair dryerPrivate resting rooms (available for a fee for day-use bathing)
House rules
All guest rooms are non-smoking. Curfew is 9 PM. A separate hot spring tax is required (150 yen per person). Day-use bathing is limited to outdoor baths only. Bathing is not permitted outside of day-use reception hours.
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

Ubayu Onsen Masugataya

From¥19,700/ person / night (tax incl.)
4.6(92)

Approx. lowest rate (varies by date & guests)

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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