Bicarbonate Springs: "Beauty Waters" for Smooth, Glowing Skin

Takanoyu rises by its own pressure from a drilled well on the northern foot of Mount Asama, right beside the Agatsuma Line, and travels about 80 meters by pipe to the baths. Its signature is balance: chloride, sulfate and bicarbonate dissolve in nearly equal measure, so one soak offers the warmth of a salt spring, the softness of a sulfate spring and the smoothness of a bicarbonate spring. Iron leaves brown deposits on the spouts and turns the water a cloudy green-brown on contact with air, a generous spring made for chilly highland nights.

Horoka Onsen lies in the mountains east of the Daisetsuzan range, north of Lake Nukabira, and is said to have been found in 1928 during pulpwood logging. Springs A to F dot the valley and hillside, and Source E has long been nicknamed the '硫黄泉' bath. In fact it is a neutral sodium chloride-bicarbonate water holding 247.5 mg/kg of free carbon dioxide, smooth on the skin with a gentle salty taste. It suits travellers who want a quiet, unhurried soak deep in the forest.

The Shari Onsen source gushed from a 1,000 m borehole in 1976 beside the Shari River near the town center of Shari, the gateway to Shiretoko. Drilling began after a slope was spotted where snow melted first each spring, and the water has since been piped to local inns, a community rest house and nearby homes. Clear and pale brown like oolong tea, this moor water carries plant-derived humus, and its slippery touch leaves skin soft and smooth, gently easing the fatigue of travel.

Pumped from 1,000 meters beneath the Kuju Highlands in Aso-Kuju National Park, the Tenku no Daichi Kuju Kogen Hotel source is a true all-star spring, combining the properties of chloride, sulfate, and bicarbonate waters. Rich in metasilicic acid, a natural moisturizer, it leaves skin feeling smooth during the bath and wonderfully soft afterward. It's perfect for days when you want to deeply soothe body and soul while gazing at the majestic nature of the Kuju mountain range and Mount Aso.

Nigoriyu bubbles up beside the Seri River in Nagayu Onsen, a village famed for carbonated springs, and was once known as the "high-temperature Ramune spring." Clear at the source, its iron content oxidizes into a tea-brown cloud in the bath, giving the spring its name. Around 40°C, the water lingers on the skin with fine bubbles and a silky, clinging feel, suiting bathers who want a long, gentle soak.

Ikaho is an ancient spa praised in the Man'yoshu poetry anthology. In the Warring States era its stone-step street was laid out as a healing retreat for soldiers wounded at Nagashino, and the koma-guchi system that divides the spring water among the inns survives today. Kogane-no-yu rises clear, but its iron oxidizes in the air and tints the water tea-brown, as its golden name suggests. This neutral water rich in sulfate and bicarbonate warms the body to the core and has long been called a spring for fertility. It is a bath that carries Ikaho's history itself.

This spring in a deep valley near the source of the Yoshino River is said to have flowed since ancient times. After the old spring was submerged by a dam reservoir, it was found again by boring into the valley, and it still rises by its own pressure. It combines 2,127 mg/kg of bicarbonate with 920 mg/kg of chloride, and 142 mg/kg of free carbon dioxide gives it a fizzy, slightly sweet and faintly metallic taste. Thick mineral deposits crust the tub edges. At just over 39°C, it suits those who like to lose track of time in a lukewarm bath overlooking the gorge.

Kamioka Onsen flows on its own, without pumps, from a 170 m well drilled in 1957 in Beppu's Kannawa district. A 2025 analysis recorded 89.5°C and pH 9.0: an unusual alkaline sulfur spring in a town known for acidic sulfur waters, its sulfur dissolved as hydrosulfide ions rather than gas. Sodium 228.0 mg/kg, bicarbonate 279.0 mg/kg, sulfate 184.0 mg/kg and metasilicic acid 339.0 mg/kg give a clear water with a faint sulfur scent and a quiet, deeply comforting character.

Namegawa Onsen, one of the eight hot springs of Yonezawa, is a mountain healing retreat in the Azuma range said to have opened in the Edo period with permission from the Uesugi domain. The Uenoyu source gushes beside the Maekawa stream, its bluish milky-white water carrying a gentle scent of sulfur. The water feels weighty and smooth, leaving the skin soft and light after bathing. Deep in the mountains, it suits those who want a quiet soak to the sound of the gorge.

The Shiroyu source is one of four springs of differing character that rise within about 50 meters of one another at Yunotai, said to be the oldest bathing ground of Nyuto Onsen, where records of a spa date back to the Edo period. Long called the "beauty spring" and the "spring for chills," it bubbles up beneath an open-air bath and is also piped to nearby lodgings. Its bluish, cloudy water carries a gentle sulfur scent and a soft, smooth touch, leaving skin supple and warmth that lingers long after a soak, a spring for anyone who wants to unwind slowly in the beech forest.

Nestled quietly in the mountainous region of Toyama Prefecture, Ogawa Onsen gushes forth. This naturally gushing spring, cherished by locals for generations, delivers the pure blessings of the earth. Its mild, neutral waters gently embrace the body, while a subtle veil of salt ensures a restorative warmth that lingers. Guests will also experience the benefit of silky skin, feeling remarkably light and refreshed after their soak. It is highly recommended for those seeking deep relaxation from daily fatigue, and those desiring gentle comfort for cold sensitivity or gastrointestinal discomfort.

Tokachigawa Onsen is famed for its "moor" water, which rises through layers of ancient plant deposits and was named a Hokkaido Heritage in 2004. This source blends three wells at the town's distribution station and is piped widely to inns along the river. Its faint amber water feels soft thanks to humic matter and bicarbonate, leaving skin moist, while the chloride content holds the warmth, a spring for those who want to warm up deeply under the clear skies of the Tokachi Plain.

The Gaga Onsen source gushes naturally from the Nigorigawa gorge on the eastern flank of the Zao range, and its name is said to come from the craggy, towering cliffs that line the valley. Long treasured as a spring for the stomach and intestines, its clear, gentle water glides softly over the skin when you steep in it. It suits travelers who seek quiet time with the water deep in a mountain gorge to restore body and mind.

This spring rises on a plateau wrapped in old-growth beech forest at the foot of Mt. Akita-Komagatake, the gateway to Nyuto Onsen. Unlike the milky sulfur springs that dominate the area, it is a brownish bicarbonate water that leaves the skin slippery and smooth, with a faint tart taste and a hint of iron. It is warmed in the deep-snow winter months, and invites a side-by-side comparison with the area's white sulfur waters while you take in fresh green or autumn leaves.

Nukabira Gensenkyo spreads near Lake Nukabira on the east side of Daisetsuzan National Park, where each inn has its own source and all offer free-flowing water. Nukabira Onsen Hotel opened in 1929 as the Ryokan Fukushimakan, and the founding family still tends its bath. The source, which flows naturally on the grounds, is clear and nearly tasteless and odorless. With a balance of chloride and bicarbonate, it warms the body while feeling smooth on the skin. Two tubs, hot and medium, let you choose your temperature and linger in the mountain water.

Ikaho is an ancient spa praised in the Man'yoshu poetry anthology. In the Warring States era its stone-step street was laid out as a healing retreat for soldiers wounded at Nagashino, and the koma-guchi system that divides the spring water among the inns survives today. Kogane-no-yu rises clear, but its iron oxidizes in the air and tints the water tea-brown, as its golden name suggests. This neutral water rich in sulfate and bicarbonate warms the body to the core and has long been called a spring for fertility. It is a bath that carries Ikaho's history itself.

Ikaho is an ancient spa praised in the Man'yoshu poetry anthology. In the Warring States era its stone-step street was laid out as a healing retreat for soldiers wounded at Nagashino, and the koma-guchi system that divides the spring water among the inns survives today. Kogane-no-yu rises clear, but its iron oxidizes in the air and tints the water tea-brown, as its golden name suggests. This neutral water rich in sulfate and bicarbonate warms the body to the core and has long been called a spring for fertility. It is a bath that carries Ikaho's history itself.

Kowakidani Onsen, once known as 'Kojigoku' (Small Hell) due to its fumaroles, was renamed in 1873 following Emperor Meiji's visit. This mixed spring, combining multiple sources developed since the late Meiji era, stands as one of Hakone's most iconic hot springs. Its waters envelop the skin in a comforting salt veil, delivering restorative warmth deep into the body's core. This mellow, historically rich spring is highly recommended for those seeking deep relaxation and a profound reset from daily life.

Hot springs opened on the shore of caldera Lake Shikotsu in 1915, and until a road was built the area could be reached only by boat. It is known for a pool where water wells up through the gravel underfoot, and several sources of the same spring type flow nearby. At 50.3°C, the No. 1 Well is among the hottest. Chloride, bicarbonate and sulfate dissolve in balance, rich enough to build mineral deposits around the spout, suiting anyone who wants to warm up quietly while gazing at the lake.

Ikaho is an ancient spa praised in the Man'yoshu poetry anthology. In the Warring States era its stone-step street was laid out as a healing retreat for soldiers wounded at Nagashino, and the koma-guchi system that divides the spring water among the inns survives today. Kogane-no-yu rises clear, but its iron oxidizes in the air and tints the water tea-brown, as its golden name suggests. This neutral water rich in sulfate and bicarbonate warms the body to the core and has long been called a spring for fertility. It is a bath that carries Ikaho's history itself.

Ryujin Onsen is an ancient spa said to have been discovered by the ascetic En no Gyoja and opened by Kobo Daishi after a dream of the dragon king Nanda; in the Edo period it was a favored retreat of the lords of Kishu. Shimo-no-yu flows naturally beside the Hidaka River, and its bicarbonate-rich water gently lifts away old skin, leaving a silky feel. Counted among Japan's three great beauty springs, it has long welcomed travelers seeking smoother skin.

Shin Awanoyu Gensen rises in Shirahone Onsen, a mountain spa village in the Northern Alps known for its milky waters. Clear at the moment it emerges, the water turns pale blue-white as it meets the air, with white mineral flakes drifting through it. At about 36°C, close to body temperature, carbon dioxide gathers on the skin as fine bubbles amid a faint sulfur scent, suiting bathers who prefer to linger for hours rather than hurry through a hot soak.

Rising near Lake Kuccharo, a famed stopover for migrating swans close to the Sea of Okhotsk, Hamatombetsu Onsen has long warmed this northern lakeside town. Sodium-rich, with chloride and bicarbonate in near balance, it offers both smoothness and lasting warmth, and its unusually high metaboric acid adds a distinctive character to this quiet lakeside spring.

The Niseko-cho source is pump-lifted from the base of Niseko Annupuri International Ski Resort. Developed by the Hokkaido Chuo Bus Group, its colorless, clear waters are widely supplied to nearby hot spring facilities. Drawn from abundant natural forests, this spring offers a soft touch and provides restorative warmth, gently heating the body to its core. A subtle salt veil envelops the skin, leaving a lasting warmth that offers deep relaxation for bodies fatigued from outdoor activities. It is highly recommended for those seeking rejuvenation amidst grand nature.

Tokachigawa Onsen is famed for its "moor" water, which rises through layers of ancient plant deposits and was named a Hokkaido Heritage in 2004. This source blends three wells at the town's distribution station and is piped widely to inns along the river. Its faint amber water feels soft thanks to humic matter and bicarbonate, leaving skin moist, while the chloride content holds the warmth, a spring for those who want to warm up deeply under the clear skies of the Tokachi Plain.

Togatta Onsen is said to date back to the early Edo period, growing along the Matsukawa River that flows from the Zao range. This high-temperature well holds 296.0 mg of sodium, with bicarbonate (320.3 mg), sulfate (224.5 mg) and chloride (196.9 mg) in nearly equal shares. With 117.2 mg of metasilicic acid it feels silky on the skin. Wrapped in brown mineral flakes, it is like a quiet, wise elder of the forest.

Struck in 1979 by a local shopkeeper who drilled 1,020 meters beneath the port town of Shari, at the base of the Shiretoko Peninsula, this source rises through the peat beds under the Shari Plain. That journey gives it plant-derived humic matter and a pale amber tint, placing it among Hokkaido's celebrated moor springs. Bicarbonate makes the alkaline water feel soft, while a faint saltiness hints at the nearby Sea of Okhotsk. It has long served locals and working travelers as an unpretentious everyday bath.

Beppu Onsen, one of the eight hot spring districts of Beppu, is the historic heart of the city, with springs rising in the streets between the station and the sea. This water blends two wells drilled in seaside Kitahama in equal parts. Sea-born salt and bicarbonate dissolve in nearly equal measure, pairing lasting warmth with a smooth feel on the skin in a gentle, neutral, pale-yellow bath.

This is one of the most well-known sources in Noboribetsu, a leading onsen destination in Hokkaido. It continuously flows at a high temperature of 96.5°C, embodying the raw power of the earth. The highly acidic water, with a pH of 2.2, provides a tingling sensation on the skin and a refreshing feeling after bathing. Its rich iron and sulfate content offers a powerful bathing experience that feels as if it's awakening both mind and body. It's a spring for those who wish to reset from daily fatigue, gain new vitality, and feel nature's energy throughout their entire being.

Drawn from 700 meters beneath the center of Oita City, this private source is a true urban oasis. The Ariston Hotel Oita source boasts a pH of 8.6 and abundant bicarbonate ions, which gently exfoliate the skin, leaving it remarkably smooth. Its amber-hued waters invite deep relaxation, melting away the day's fatigue. It is perfect for those seeking to refresh and rejuvenate after a day of business or sightseeing.

Nagayu Onsen gushes along the Seri River at the eastern foot of the Kuju mountains in Naoiri, Taketa, and is celebrated as one of Japan's leading carbonated-spring towns, long praised as water that works both when drunk and when soaked in at length. The Daimaru Ryokan source rises at 46.8°C and carries a rich 4,480 mg/kg of minerals, led by 2,160 mg of bicarbonate and 263 mg of magnesium, plus 735 mg of free carbon dioxide. Its greenish, cloudy water leaves rust-brown scale-like deposits on tub edges and spouts.

Said to have been found by gold prospectors some four centuries ago, this lukewarm source rises beside a mountain stream deep in the Iide range. Bath huts stood here by the late Meiji era, when visitors walked hours along forest trails to reach it. Carbon dioxide drives the water up from a drilled well, periodically sending a column of spring water into the air. Its tea-brown water tastes bitter and faintly of iron, rewarding those who seek remote, unhurried soaks.

Usuki Onsen was drilled to 1,300 m near the old castle town of Usuki, long known as a place without hot springs. Formerly called a "bicarbonate-salt spring", it emerges colorless and clear with a faint salty taste. Its weakly alkaline bicarbonate softens the skin surface for a remarkably slippery feel, while the chloride keeps warmth lingering after the bath. It suits travelers who want to warm up gently after strolling the stone Buddhas and castle-town lanes.

Yakumo Onsen lies in forested hills along the Namarikawa River on the Oshima Peninsula. Water from Namarikawa Well No. 3 is rich in bicarbonate and chloride and carries over 410 mg/kg of free carbon dioxide. It carries a faint scent of iron and is concentrated enough for mineral crystals to float on the surface. Slightly salty, it warms the body to the core while leaving the skin moist and smooth, suiting those who want a long, unhurried soak in mineral-rich water to the sound of the river.

This private source, Kusunoyu, gushes forth in the Beppu Onsen area, one of the eight springs of Beppu. While its name is associated with the historic "Kusunoki Onsen" public bath dating back to the Kamakura period, that bathhouse is now closed. This source features a balanced blend of skin-smoothing bicarbonate ions and core-warming chloride ions at a gentle pH of 8.2. As you steep in its waters, the slightly viscous texture envelops your skin, leaving it feeling moisturized and restoratively warm long after you emerge. It is perfect for those seeking to unwind both body and soul in a historic spa town.

Nestled in Noboribetsu Onsen, famously called the "Department Store of Hot Springs" and rooted in the Ainu "Nupur-pet" (deeply colored river), the historic "Uma no Yu" source has flowed since Taisho 6 (1917). Its faint sulfur aroma gently unwinds the mind and body. The waters, softly enveloping the skin, warm the body to its core, providing restorative warmth that lingers. Overlooking a beautiful Japanese garden, this tranquil spring offers deep relaxation, a serene escape from daily commotion.

Nukabira Gensenkyo began in the Taisho era when water hot enough to boil eggs was found deep in a primeval forest; the name is said to come from the Ainu word "Nukabira," a cliff shaped like a person. Kosenchi No. 1 flows naturally in the south district of the spa village, sustaining the free-flowing baths that the village's inns pledged together in their 2007 "Gensen Kakenagashi Declaration." Clear and nearly tasteless and odorless, the water is gentle on the skin and leaves a light, fresh feeling, suiting those who want to soak amid forest stillness, wild deer and starry skies.

Ikaho is an ancient spa praised in the Man'yoshu poetry anthology. In the Warring States era its stone-step street was laid out as a healing retreat for soldiers wounded at Nagashino, and the koma-guchi system that divides the spring water among the inns survives today. Kogane-no-yu rises clear, but its iron oxidizes in the air and tints the water tea-brown, as its golden name suggests. This neutral water rich in sulfate and bicarbonate warms the body to the core and has long been called a spring for fertility. It is a bath that carries Ikaho's history itself.

Kuroyu is one of four springs of differing character that rise within about 50 meters of one another at Yunotai, said to be the oldest bathing ground of Nyuto Onsen. Long called the "warm-pool spring" and the "spring of fertility," it has the highest chloride content of the four, so a soak warms you to the core and the heat lingers long afterward. The cloudy, sulfur-scented water comes up hot and is tempered with fresh water in some seasons, a robust spring that shows its true worth during deep-snow winter stays.

Nestled at the foot of the Northern Alps in Okuhida Onsen-go, 'Fuku no Yu' (Spring of Fortune) is a blessed hot spring said to bring good fortune to its visitors. With a gentle, skin-friendly neutral pH of 7.2, its abundant bicarbonate ions wash away old skin cells, leaving your skin smooth to the touch. As you immerse yourself in the water, you'll feel the hustle and bustle of daily life fade away, accompanied by a faint scent of sulfur. This calm and pure spring embraces all who wish to reset their mind and body and gain new vitality.