Sauna by the river. Cooling off outside is essential part of sauna experience. Picture: Mika Meskanen
A sauna is a small room or building designed as a place to experience dry or wet heat sessions, or an establishment with one or more of these and auxiliary facilities. The steam and high heat make the bathers perspire.
The word sauna is an ancient Finnish word referring to the traditional Finnish bath and to the bathhouse itself. In Baltic-Finnic languages other than Finnish, sauna does 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.
In Europe, the Nordic countries have a sauna tradition. The Finnish sauna culture is well established, there are built-in-saunas in almost every house in Finland. The oldest known saunas in Finland 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 over 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.
Traditional smoke sauna. The smoke colors the walls inside the sauna. The rocks form the stove. Picture: Riku Kettunen
The first Finnish saunas are what nowadays are called savusaunas, or smoke saunas. These differed from present-day saunas in that they were heated by heating a pile of rocks called kiuas by burning large amounts of wood about 6 to 8 hours, and then letting the smoke out before enjoying the löyly, or sauna heat. A properly heated ”savusauna”gives heat up to 12 hours.
Heating the smoke sauna. There are no chimenys in smoke saunas. Picture: Mika Meskanen
As a result of the industrial revolution, the sauna evolved to use a metal woodstove, or kiuas, with a chimney. Air temperatures averaged around 70–80 degrees Celsius (160–180 degrees Fahrenheit) but sometimes exceeded 90 °C (194 °F) in a traditional Finnish sauna. When the Finns migrated to other areas of the globe they brought their sauna designs and traditions with them. This led to further evolution of the sauna, including the electric sauna stove, which was introduced in 1938 by Metos Ltd in Vaasa.
Although the culture of sauna nowadays is more or less related to Finnish culture, the evolution of sauna happened around the same time both in Finland and the Baltic countries sharing the same meaning and importance of sauna in daily life, shared still to this day.
Throwing water on the stove. Picture: Visit Lakeland
The hottest Finnish saunas have relatively low humidity levels in which steam is generated by pouring water on the hot stones. This allows air temperatures that could boil water to be tolerated and even enjoyed for longer periods of time.
In a typical Finnish sauna, the temperature of the air, the room and the benches is above the dew point even when water is thrown on the hot stones and vaporized. Thus, they remain dry. In contrast, the sauna bathers are at about 38 °C (100 °F), which is below the dew point, so that water is condensed on the bathers’ skin. This process releases heat and makes the steam feel hot.Typical sauna stove nowadays. Picture: Riisipuuro
Finer control over the temperature experienced can be achieved by choosing a higher level bench for those wishing a hotter experience or a lower level bench for a more moderate temperature. A good sauna has a relatively small temperature gradient between the various seating levels. Doors need to be kept closed and used quickly to maintain the temperature inside.
When in the sauna users often sit on a towel for hygiene and put a towel over the head if the face feels too hot but the body feels comfortable. Most adjustment of temperature in a sauna comes from,
- amount of water thrown on the heater, this increases humidity, so that sauna bathers perspire more copiously
- length of stay in the sauna
- positioning when in the sauna
Heating caused by direct radiation will be greatest closest to the stove. Heating from the air will be lower on the lower benches as the heat rises. Provided the sauna is not crowded, lying on a bench is considered preferable as it gives more even temperature over the body. Heating caused by fresh steam can be very different in different parts of the sauna. As the steam rises directly upwards it will spread across the roof and travel out towards the corners, where it will then be forced downwards.
Consequently, the heat of fresh steam may sometimes be felt most strongly in the furthest corners of the sauna. Users increase duration and the heat gradually over time as they adapt to sauna.
When pouring water onto the heater, it will cool down the heater, but carry more heat into the air via advection, making the sauna warmer.
Perspiration is a sign 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 temperature, but management and otherusers expect to be consulted before changes are made. The sauna heater and rocks are very hot – one must stay well clear to avoid injury, particularly when water is poured on the sauna rocks, which creates an immediate blast of steam.
Contact lenses dry out in the heat. Jewellery or anything metallic, including glasses, will get hot in the sauna and can cause discomfort or burning.
Cooling down is a part of the sauna cycle and is as important as the heating. Among users 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 by stepping into it gradually, rather than immediately immersing fully. In summer, a session is often started with a cold shower.Birch twigs are used in sauna in summer time. Picture: Jari Latvala
A sauna session can be a social affair in which the participants disrobe and sit or recline in temperatures typically between 70 and 100 °C (158 and 212 °F). This induces relaxation and promotes sweating. The Finns use a bundle of birch twigs with fresh leaves, to gently slap the skin and create further stimulation of the pores and cells.
The sauna was (and still is) an important part of daily life, and families bathed together in the home sauna. There are at least 2 million saunas according to official registers. Finnish Sauna Society believes the number can actually be as high as 3.2 million saunas (population of Finland is 5.4 million).