What kind of 'onsen' are there?
About onsen quality
Onsen are commonly effective as a result of mineral activity and temperature. Depending on the quality of the spa, the unique characteristics can vary. The quality and type of onsen is determined according to a number of groups such as the mineral content found in the spring water, and the quantity
Onsen Quality Feature
Simple Onsen Even if the hot spring has a temperature of 25 degrees, the overall mineral composition within 1kg water adds up to less than 1000mg. The level of stimulation is low, but there will potentially be a wide range of effects when used.
Carbon Dioxide Onsen A 'Carbon Dioxide Onsen' is where in 1kg of hot spring water, there is 100mg or more of released carbonic acid. This causes carbon dioxide to dissolve, creating a fine froth on the surface, and it is often referred to as a 'bubbly spa' or 'soda spa'. The onsen has the effect of expanding blood vessels, helping to lower blood pressure.
Sodium Bicarbonate Saline Onsen This type of onsen is alkaline, and there are two different types: Sodium Bicarbonate and Bicarbonate Earth Onsen. It is a clear colour and has the ability to make skin feel smooth, and in particular sodium bicarbonate makes skin soft and gentle, while removing dirt, often being called 'the water of beautiful skin'.
Chloride Onsen Containing salt similar to the kinds found in sea water, the salt has the effect of controlling perspiration after bathing, also means that the body's ability to retain heat is also excellent. This type of onsen is known as 'Fever water'.
Sulphate Onsen The spring water, with a bitter taste when drunk, has been known as 'Water for cuts and bruises'. Sulphate onsen are divided into three categories: Calcium sulphate, Sodium sulphate, containing traces of natrium, and a regular bitter spring which contains traces of magnesium.
Ferruginous Onsen (Iron) There are two types of Ferruginous Onsen: Carbonated Iron Onsen, and Melanterite Onsen. The water is a colourless, transparent as it gushes up, but as it comes into contact with the atmosphere, it develops into a dark reddish-brown colour and weakens the waters effect. This type of spring helps the body's ability to retain heat, and when drunk replenishes the body's iron levels.
Aluminium Onsen Colourless and transparent, or a yellowish-brown colour with a bitter taste, these acidic springs have strong sterilising properties.
Cupriferous/Ferruginous Onsen (Copper and Iron) Similar to the Ferruginous spring, the water oxides with the atmosphere once exposed, becoming an opaque yellow colour, and leaving a red-brown sediment. Because there are traces of iron in the spring, the temperature can be very hot, but this kind of onsen is not very effective for cleaning the body.
Sulphur Onsen With the distinctive and unique smell of bad eggs, this kind of spring has the ability to expand the blood vessels in the body. Because the hydrogen sulphide in the spring is toxic, proper ventilation is essential. The pale-yellow sediment are known as 'Hot water flowers'. The sulphur can soften the hardened keratin of the skin, and is also good for acne and spots.
Acidic Onsen This type of spring has powerful sterilising properties, and a strong stimulation that permeates the skin. Acidic Onsen are not recommended for people with sensitive skin or weak health.
Radioactive Onsen Only tiny amounts of radioactive minerals are found in this type of hot spring, and it can also be referred to as a 'Radium Onsen' or 'Radon Onsen'. Strong evidence has been recorded that shows the miniscule amounts of radioactivity in the water have a beneficial effect on the body.
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