Water profile

Hotel Hanakoyado

Spring chemistry and what it does, with the research behind it.

極楽泉源Gokuraku Spring Source

塩ChlorideSodium Chloride spring

Gokuraku Sengen, rising in Arima-cho in Kobe's Kita ward, is a sodium chloride spring (hypertonic, neutral, high-temperature class) that flows up under its own pressure at just over 98 °C — among Japan's hottest natural sources. The certificate records water that is colorless and clear at the wellhead with a strongly salty taste, developing a brown sediment within hours of sampling. Richly mineralized and hypertonic, it is a classic heat-retaining chloride bath, and with nearly 100 mg/kg of metasilicic acid it edges into the beauty-water family, leaving skin feeling smooth and moisturized. The indications sheet documents it for cuts, peripheral circulation disorders, cold sensitivity, and dry skin.

Good for

Warming

Salt forms a film on the skin that slows heat loss, so the warmth lingers long after the bath (the classic heat-keeping water, nettō 熱の湯).

cold sensitivity

On the certificate:Cold sensitivity

Aches & joints

Warmth eases stiffness and raises the pain threshold. Radon and sulfate springs show the strongest evidence for joint and muscle pain.

stiff shoulders

On the certificate:Muscle stiffness associated with motor paralysis

Smooth skin

Bicarbonate and alkalinity gently lift dead keratin while silica hydrates, leaving skin smooth. This is the basis of the beautifying-water (bijin-no-yu 美人の湯) reputation.

dry, rough skin

On the certificate:Dry skin

Cuts

Mineral-rich chloride, sulfate and sulfur waters have a long-recorded soothing effect on minor cuts and slow-healing skin.

minor wounds

On the certificate:Cuts

Recovery

Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.

fatigue, stress

On the certificate:Autonomic nervous system instabilityConvalescenceFatigue recoveryGeneral health improvementDepressed mood

Take care

Contraindications

Active stage of any illness (especially with fever)
Active tuberculosis
Advanced malignant tumor or severe anemia with marked physical weakness
Severe heart or lung disease causing breathlessness on slight exertion
Severe kidney disease with edema
Gastrointestinal bleeding
Visible bleeding
Acute exacerbation of a chronic illness

Full composition

The bar is each ion's share of charge (mval%) within its group; over 20% names the spring. Gases, silica and trace metals are measured by mass only.

Cationsshare of charge (mval%)

Sodiumsalt's cation — pairs with chloride to make the water saltyNa⁺4,336mgP96 national81%
Calciumsettling and calming; can leave a white mineral bloomCa²⁺443mgP91 national9%
Potassiumminor; matters for drinking limitsK⁺813mgP99 national9%
Iron (II)Fe²⁺11.4mgP90 national0.2%
MagnesiumMg²⁺5.0mgP51 national0.2%
AmmoniumNH₄⁺2.0mgP79 national0.1%
ManganeseMn²⁺2.5mgP95 national0.0%
ZincZn²⁺1.4mgP96 national0.0%
AluminumAl³⁺0.20mgP69 national0.0%

Anionsshare of charge (mval%)

Chloridetable-salt anion — coats the skin and holds heat inCl⁻7,930mgP95 national95%
Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻630mgP80 national4%
SulfateSO₄²⁻17.0mgP31 national0.1%
BromideBr⁻14.8mgP89 national0.1%
FluorideF⁻1.7mgP57 national0.0%
Hydrogen sulfideHS⁻0.50mgP57 national0.0%
IodideI⁻1.9mgP85 national0.0%
CarbonateCO₃²⁻0.30mgP13 national0.0%
Thiosulfateoxidized sulfurS₂O₃²⁻< —mg

Non-dissociatedmeasured by mass

Metaboric acidmetaboric acid — mildly antibacterialHBO₂130mgP96 national
Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃99.9mgP57 national

Dissolved gasesmeasured by mass

Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂104mgP81 national
Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S0.40mgP69 national

Trace metalsmeasured by mass

Mercurytoxic trace — part of the drinking-safety checkHg0.0009mgP54 national
ArsenicAs< —mg
CadmiumCd< —mg
CopperCu< —mg
LeadPb< —mg

Measured at the source

7.10

Neutral

Source temperature

98.1°C

Hot

Tonicity

14.44g/kg

Hypertonic

Flow rate

66L/min

Typical

Free CO₂

104mg/kg

Low

Free H₂S

0.40mg/kg

Low

On the certificate

Chronic muscle or joint pain and stiffness (rheumatoid arthritis, osteoarthritis, lower back pain, neuralgia, frozen shoulder, bruises, sprains — chronic phase)
Reduced gastrointestinal function (heaviness, bloating)
Mild hypertension
Impaired glucose tolerance (diabetes)
Mild hypercholesterolemia
Mild asthma or emphysema
Hemorrhoid pain
Stress-related symptoms (sleep disorders)
Peripheral circulation disorders

Evidence

妬泉源Uwanari Spring Source

鉄Iron-bearingSodium Chloride spring · +塩化物強塩泉

Uwanari Sengen, also rising in Arima-cho in Kobe's Kita ward, is an iron-bearing sodium chloride strong-salt spring (hypertonic, neutral, high-temperature class) that surges up on its own at over 100 °C. Dissolved solids of 37.6 g/kg put it well beyond ocean salinity — a classified strong-salt spring whose thick mineral coating keeps the body warm long after the bath. The water is iron-rich: colorless and clear at the wellhead, the certificate notes it develops a green sediment and pale-green turbidity within hours of sampling. Generous metasilicic acid adds a skin-smoothing note, and the indications sheet documents the water for cuts, peripheral circulation disorders, cold sensitivity, and dry skin.