Q & A
Frequently Asked Questions
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Where is the analysis certificate displayed?
It is typically posted in the changing room or near the entrance to the bathing area. If you cannot find it, ask the front desk staff.
Is it a problem if the certificate is old?
The Hot Spring Act requires renewal every ten years. A certificate more than ten years old is overdue for renewal. However, if there have been no significant changes to the spring, the fundamental characteristics remain valid.
Legal Basis for the Certificate
Under Article 18 of Japan's Hot Spring Act, any facility offering hot spring water for bathing or drinking must display the analysis certificate inside the bathing area. Analysis must be conducted by a prefectural government-registered body and renewed every ten years.
Key Items Listed on the Certificate
- Spring name, location, and analysis dateThis identifies the specific hot spring source and when its water was analyzed. The analysis must be renewed every 10 years as required by law, ensuring the data on the certificate is up-to-date.
- Flow rate, source temperature, and pHThese are the spring's core physical properties. The pH value indicates its acidity or alkalinity, affecting how the water feels on the skin, while the source temperature determines if heating is necessary for bathing.
- Major components (cations, anions, undissociated components, dissolved gases) in mg/LThis section details the chemical makeup of the water, listing the concentration of dissolved minerals and gases in milligrams per liter. These components are what give each onsen its unique characteristics and therapeutic potential.
- Official spring type (with classification basis)Based on the major chemical components, the spring is given an official classification like "Sulfate Spring" or "Simple Spring." This name provides a quick summary of the water's primary characteristics and expected benefits.
- Bathing and drinking indications and contraindicationsThis lists the health conditions that may benefit from the onsen's specific properties (indications), as well as conditions for which bathing is not advised (contraindications). This guidance applies to both bathing and, where permitted, drinking the water.
- Bathing notes: whether water is heated, diluted, circulated, or disinfectedThis explains how the water is treated before it reaches the tub. It reveals whether the water is pure and free-flowing from the source (gensen kakenagashi) or if it has been heated, diluted, filtered, or disinfected.
What to Focus On
- pH: low = acidic, high = alkaline; affects skin stimulationThe pH value measures the water's acidity (low pH) or alkalinity (high pH). This is a primary factor influencing the sensation on your skin, ranging from mildly stimulating to soft and smooth. Pay attention to this number to anticipate the water's feel.
- Metasilicic acid & metaboric acid: trace components associated with skin-softening benefitsThese are trace components often noted for their reputed 'skin-beautifying' properties. Their presence in the water is believed to contribute to a moisturizing and softening effect on the skin. Checking for these ingredients can help you identify springs known for these benefits.
- Free carbon dioxide: ≥ 2,000 mg/L qualifies as a carbon dioxide springThe concentration of free carbon dioxide is the key metric for identifying a carbonated spring (炭酸泉, tansansen). To officially qualify as such, the water must contain at least 2,000 mg/L of this component. This specific threshold is a critical piece of data on the analysis certificate.
- Heating / dilution notes: key to identifying "source-flow" (kakenagarashi) springsThis section is vital for understanding how the onsen water is managed before it reaches the tub. It specifies if the water is heated (加温, kaon) or diluted (加水, kasui). These notes are essential for determining if a bath is 'kakenagarashi' (source-flow) or has been treated.
References
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