Sauna

thumb|A modern [[Finnish sauna]]

A sauna (, ) is a room or building designed as a place to experience dry or wet heat sessions or an establishment with one or more of these facilities. The steam and high heat make the bathers perspire. A thermometer in a sauna is used to measure temperature; a hygrometer can be used to measure levels of humidity or steam.

History

thumb|A Finnish smoke sauna

Areas such as the rocky Orkney islands of Scotland have many ancient stone structures for normal habitation, some of which include dedicated areas for fire and bathing. It is possible some of these structures also incorporated the use of steam in a way similar to the sauna, but this remains speculative. The sites are from the Neolithic age, dating to approximately 4000 B.C.E. Archaeological sites in Greenland and Newfoundland have uncovered structures very similar to traditional Scandinavian farm saunas, some with bathing platforms and "enormous quantities of badly scorched stones".

The traditional Korean sauna, called the hanjeungmak, is a domed structure constructed of stone that was first mentioned in the Sejong Sillok of the Annals of the Joseon Dynasty in the 15th century. Supported by Sejong the Great, the hanjeungmak was touted for its health benefits and used to treat illnesses. Korean sauna culture and kiln saunas are still popular today, and Korean saunas are ubiquitous.

thumb|Women in Sauna with [[sauna whisk|vihtas in the middle of the 20th century in Finland|alt=]]

Western saunas originated in Finland where the oldest known saunas were made from pits dug in a slope in the ground and primarily used as dwellings in winter. The sauna featured a fireplace where stones were heated to a high temperature. Water was thrown on the hot stones to produce steam and to give a sensation of increased heat. This would raise the apparent temperature so high that people could take off their clothes. The first Finnish saunas were always of a type now called savusauna; "smoke sauna".

thumb|Bain Finlandais. Illustration of a Finnish sauna in 1804 by [[Giuseppe Acerbi.]]

As a result of the Industrial Revolution, the sauna evolved to use a wood-burning metal stove with rocks on top, kiuas, with a chimney. Air temperatures averaged around but sometimes exceeded in a traditional Finnish sauna. As the Finns migrated to other areas of the globe, they brought their sauna designs and traditions with them. This led to a further evolution of the sauna, including the electric sauna stove, which was introduced in 1938 by Metos Ltd in Vaasa. Although sauna culture is more or less related to Finnish and Estonian culture, the evolution of the sauna took place around the same time in Finland and Baltic countries; they all have valued the sauna, its customs and traditions until the present day.

The sauna became very popular especially in Scandinavia and the German-speaking regions of Europe after the Second World War: German soldiers had experienced Finnish saunas when the two nations fought together against the Soviet Union (see Continuation War). Saunas were so important to Finnish soldiers that they built them not only in mobile tents but even in bunkers. After the war, the German soldiers brought the custom back to Germany and Austria, where it became popular in the second half of the 20th century.

Sauna culture has been registered in the Representative List of the Intangible Cultural Heritage of Humanity under two entries: "Smoke sauna tradition in Võromaa" in 2014 and "Sauna culture in Finland" in 2020.

Etymology

The word sauna is an ancient Finnish word referring to both the traditional Finnish bath and to the bathhouse itself. In Finnic languages other than Finnish and Estonian, sauna and cognates do not necessarily mean a building or space built for bathing. It can also mean a small cabin or cottage, such as a cabin for a fisherman. The word is the best known Finnicism in many languages.

Petri Kallio has proposed a Germanic etymology, a hypothesis which has gained some scholarly support. In this account, the word is derived from Proto-Germanic or its earlier Palaeo-Germanic form. The Germanic word is cognate with English stack and originally denoted a pile or heap, interpreted here as referring to an early sauna oven consisting of a pile of stones. The loan word would have developed into Proto-Finnic *sakna, from which the Finnish sauna later evolved. There are also many public saunas in Finland, including Rajaportin Sauna, a sauna located in Tampere, that was first established in 1906 by Hermanni and Maria Lahtinen. Helsinki even has a sauna built into one of the gondolas of a Ferris wheel, SkyWheel Helsinki. Unlike many other countries, Finnish people usually prefer to be naked instead of wearing a swimsuit, towel, or other kind of clothing.

Under many circumstances, temperatures approaching and exceeding would be completely intolerable and possibly fatal to a person exposed to them for long periods. Saunas overcome this problem by controlling the humidity.

Finer control over the perceived temperature can be achieved by choosing a higher-level bench for those wishing for a hotter experience, or a lower-level bench for a more moderate temperature.

According to the Guinness Book of World Records, the world's largest sauna is the Koi Sauna in the Thermen & Badewelt Sinsheim, Germany. It measures 166 square meters, holds 150 people, and sports a koi aquarium. The title may now belong to Cape East Spa in Haparanda, Sweden, which also holds 150 people but is more spacious.

However, in Czeladz, south Poland, there is now a sauna for 300 people, sporting light shows, theatre, and several sauna masters.

<gallery widths="200" heights="150" perrow="4">

File:Geysirhöhle.jpg|Sauna with geyser at Therme Erding

File:06 TWE Saunaparadies Stonehenge Keltenthron-Sauna Aufguss Fahne.jpg|Modern collective sauna, Erding

File:NaturTherme Templin Sauna 07.jpg|Modern sauna in Templin, Germany

File:Tjuvholmen, Sauna (2024)-L1006528.jpg|A sauna on a dock in the Tjuvholmen marina of Oslo, Norway

</gallery>

Use

thumb|Interior of a modern home sauna in Finland

thumb|A small pool for cooling down; usually filled with cold water

A modern sauna with an electric stove usually takes about 15–30 minutes to heat up. Some users prefer taking a shower beforehand to speed up perspiration in the sauna. When in the sauna, people often sit on a towel for hygiene and put a towel over their heads if the face feels too hot but the body feels comfortable. In Russia, a felt "banya hat" may be worn to shield the head from the heat; this allows the wearer to increase the heat on the rest of the body. The temperature of one's bath can be controlled via:

• the amount of water thrown on the stove: this increases humidity so that sauna bathers perspire more copiously
• the length of one's stay in the sauna
• positioning: the higher benches are hotter, whereas the lower benches are cooler. Children often sit on the lower benches.

The heat is greatest closest to the stove. Heating from the air is cooler on the lower benches as the hot air rises. The heat given by the steam can be very different in different parts of the sauna. As the steam rises directly upwards, it spreads across the roof and travels out towards the corners, where it is then forced downwards. Consequently, the heat of fresh steam may sometimes be felt most strongly in the furthest corners of the sauna. Users increase the duration and the heat gradually over time as they adapt to the sauna. When pouring water onto the stove, it cools down the rocks, but carries more heat into the air via advection, making the sauna warmer.

Perspiration is the result of autonomic responses trying to cool the body. Users are advised to leave the sauna if the heat becomes unbearable, or if they feel faint or ill. Some saunas have a thermostat to adjust the temperature, but the owner of the sauna and the other bathers expect to be consulted before changes are made. The sauna stove and rocks are very hot—one must stay well clear of them to avoid burns, particularly when water is thrown on the rocks, which creates an immediate blast of steam. Combustibles on, or near the stove have been known to cause fires. Contact lenses dry out in the heat. Jewelry or anything metallic, including glasses, will get hot in the sauna and can cause discomfort or burning. Some may wish to put an additional towel or a special cap over the head to avoid dryness. Few people can sit directly in front of the stove without feeling too hot from the radiant heat, but this may not be reflected in their overall body temperature. As the person's body is often the coolest object in a sauna room, steam will condense into water on the skin; this can be confused with perspiration.

Cooling down by immersing oneself in water (in a shower, lake, or pool) is a part of the sauna cycle and is as important as the heating. However, healthy people and heart patients alike should take some precautions if plunging into very cold water straight after coming from the hot room, as the rapid cooling of the body produces considerable circulatory stress. It is considered good practice to take a few moments after exiting a sauna before entering a cold plunge and to enter a plunge pool or a lake by stepping into it gradually, rather than immediately immersing oneself fully. In summer, a session is often started with a cool shower.

In some countries, the closest and most convenient access to a sauna is at a gymnasium. Some public pools, major sports centers, and resorts also contain a sauna. Therapeutic sauna sessions are often carried out in conjunction with physiotherapy or hydrotherapy; these are gentle exercises that do not exacerbate symptoms.

Health effects

Potential health benefits

There has been widespread research into the health benefits and risks that come from sauna usage; most studies have focused on the Finnish sauna specifically. Sauna bathing leads to mild heat stress, which activates heat shock proteins responsible for repairing misfolded proteins, promoting longevity as well as protection against muscle atrophy and chronic illness.

There is evidence that long-term exposure to Finnish-style sauna is correlated with a reduced risk of sudden cardiac death; and that risk reduction increases with duration and frequency of use; Evidence exists for the benefit of sauna on people with heart failure. Frequent Finnish-style sauna usage (4-7 times per week) is associated with a decreased risk of neurovascular diseases, including Alzheimer's disease and stroke, It also is associated with a reduced risk and symptom relief from respiratory illness.

Evidence for the use of sauna for depression or skin disorders is insufficient, but the frequency of sauna sessions is correlated with a diminished risk of developing psychosis, and it might be beneficial for psoriasis. Being severely obese, having high blood pressure, or being diabetic all serve as reasons to decrease the duration of sauna sessions.

One study has found that genital heat stress from frequent sauna sessions could cause male infertility.