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Why is light steam so highly prized?
Light steam is so highly regarded because it holds the secret to the health benefits the traditional sauna promises. Light steam can only be properly experienced in a traditional Russian sauna. The standard temperature in the steam room of an authentic Russian sauna is 60-80°С. Light steam is produced by splashing clean, hot water onto the stove's red hot core. In a sauna with light steam, there is no sensation of burning moisture, the air remains easy to breathe and the body warms up comfortably and harmoniously.
Authentic (classic, masonry) Russian sauna stoves are the only type of stove capable of producing light steam. Thanks to its enclosed construction design, the core of a sauna stove for a Russian banya can be heated until it is glowing red hot. Once the stones reach a temperature of between 700-900°С, there is a characteristic flapping sound as the water transforms into steam, expanding instantaneously to as much as 600 times its own volume. Light steam is exceptionally fine, so much so, that its moisture content is completely indiscernible to the steam room guests.
The thermal balance achieved in the steam room on account of the stove's heated stone mass minimises air flow avoiding the risk of hot drafts which can cause burns to the skin and upper respiratory tract.
At the same time, pure air from outside the steam room is warmed to temperature before it enters the breathing zone and the air which has become saturated with vapours is extracted from the steam room. What is created is a kind of ideal microclimate to which we stove masters must aspire.
Factors of climate are experienced as a whole rather than separately. We feel the radiant heat from the stove, the difference in temperature at the level of the head and feet, air currents, etc all at the same time and all these factors together make up a microclimate. The question here is whether a microclimate can be assessed. Of course, on a subjective level, we immediately evaluate the comfort level of a surrounding microclimate and experience the consequences of its impact on the body but can this experience be measured objectively? Can certain climatic indicators be replicated in order to create a little piece of heaven in the steam room?
Here, traditional equipment used in meteorological research comes to our aid, such as Vernon's globe thermometer (Horace Middleton Vernon, British physiologist and researcher of labour conditions, 1870-1951). In Russia, this instrument is used to produce an environmental thermal load index (ETL). The environmental thermal load index, a composite indicator expressed in °С, characterises the overall impact of microclimate components on the human body (temperature, humidity, air flow speed and heat radiation). Outside of Russia, the globe thermometer is used to determine the so-called WBGT-index (Wet-Bulb Globe Temperature), which also illustrates the effect of a microclimate on the body. ETL index values are so important that they lie at the core of government norms for working conditions, sanitary and construction standards. The globe thermometer characterises human heat transfer in which heat is dissipated into the environment directly via radiation from the skin and by convection (cooling of body heat by air surrounding the body).
So, in our studies, we measured the temperature in the steam room with a dry, a wet (soaked) and a ball thermometer at the level of the floor, the benches and the ceiling, and then, by taking all the parameters into account we arrived at an ETL value (WBGT), a specific "comfort temperature". So what affects the ETL value to the greatest degree? Naturally, it is the temperature of the wet rather than the dry thermometer because this reflects the ease of the body cooling process that takes place when we sweat. As we know, high humidity levels make sweating more difficult and uncomfortable. The least influential factor is the basic room temperature.
When measuring the ETL at different heights from the floor upwards, we averaged out the values obtained. The smaller the temperature difference, the more comfortable it is to spend time in the steam room. To avoid the risk of burns, hot air flow has to be reduced to a minimum.
During our research we took WBGT index measurements in several traditional Russian steam rooms, 'banyas' with huge multi-ton furnaces ('Ussachevsky banyas', 'Gorky 10', spa hotel ‘Zhukova 2', Spa-boutique Sante de la Russie on Mosfilmovskaya St., Moscow and in a private banya in the town of Zheleznodorojhny) as well as in a public sauna equipped with a Finnish electric stove of a well known brand.
The higher the WBGT index measurement, the more pleasant the experience of the steam room. Below are some of the characteristics of the steam rooms we researched:
- Private sauna in the town of Zhelesnodorozhny, dimensions approximately 3x4x2.7 m. The Russian banya stove takes up an entire corner of the steam room. The stove's heating time lasts for approximately 5 hours in winter and 3.5 hours in summer. Once temperature has been reached, the steam room can be used for up to four days when set to family regime. WBGT - 56°C.
- In the Zhukovka-2 spa hotel sauna, all steam room processes are managed by a sauna virtuoso with 35 years experience. The sauna creates a unique steam, in which 110 degrees celsius is barely felt at all and you find yourself never wanting to leave the steam room. The stove was built in 1982 and is gas-fuelled. It has an iron core 3 tonnes in weight. WBGT - 57.5°C.
- 'Ussachevsky banyas', Moscow (10, Usacheva Street). Before our session, the steam room was prepared by a team led by one 'uncle Sasha'. Many regular sauna goers come here because of uncle Sasha's famous steam. The crowded steam room and applause that rings out when customers enter it is testimony to his skilful art. We were able to record the equipment's indicators whilst the clients were applauding. WBGT - 52°C.
- A usual sauna with an electric heater produced in accordance with modern Finnish technology. The physical sensations experienced in the steam room are characteristic of this kind of facility. WBGT - 33.7°C.
Poor substitutes of the masonry stove
In the old days, people might not have known so much but they understood a lot. Now, in life people seem to know everything but they understand very little. Just fifty years ago, literally no alternative to the authentic sauna existed. A few centuries ago, both the ‘black-style’ banya and the ‘white-style’ banya were widely used in Russia and the smoke sauna was widespread in Finland. In those days, the construction of a Russian 'black-style' banya and a Finnish sauna were almost identical. Public bathhouses were widely used in ancient Russia and remain almost totally unchanged in the principles of their design to the current day, and of course, they remain hugely popular.
Modern life has introduced great diversity into the range of sauna treatments available. In around the 1950s, as the Finnish authors describe it, a revolution took place in the field of sauna construction, which was intended to 'bury' the traditional sauna and steam room conformation. Advertising for the new invention stated that despite its low cost and simplicity, the newfangled sauna device (meaning the kind of iron bucket heater 'with rocks') boasted the same qualities as the old-style authentic sauna in terms of temperature and humidity. The problem was, that they only used a thermometer and a hydrometer to arrive at this conclusion and from that point onwards, the new type of sauna became widespread in modern life.
The finished kit designs turned out to be extremely convenient for the retail trade. As a result of the efforts of enterprising merchants, the cheap devices quickly found their way into the homes of gullible buyers.
True connoisseurs of traditional sauna and steam rooms however, were in no hurry at all to replace their old sauna constructions, tried and tested over centuries because they knew that it wasn’t that simple. A Russian sauna is in essence two things: light steam and soft heat. If we were to heat up a room and put a boiling kettle inside, would that give us a Russian banya? Not even remotely! It would generate some environmental thermal load, but very little and the conditions inside the steam room would be uncomfortable and even harmful. Aside from the right temperature and relative air humidity, creating the conditions of an authentic Russian sauna requires light steam, the absence of airflow in the steam room, an even radiant heat and even temperature distribution.
In our opinion, aside from its cheap price, the modern 'bucket with rocks' has no genuine sauna qualities going for it at all. Judge for yourself. The lightweight metal design, even if it burns firewood, has no heat storage capacity. This kind of stove has to be heated continually inviting the hazard of spending time next to a powerful source of carbon monoxide. In addition, hot air currents and the temperature difference at the level of the head and the feet both create elements of discomfort during a steam session. The stones are open and 'cold' (less than 300°С), which means they are incapable of producing light steam. Instead of the health benefits the traditional sauna promises, there is a risk of suffering skin burns, pneumonia and headaches. The statistics reflect a large number of cases of fire and carbon monoxide poisoning in this type of sauna. Aside from anything else, it is quite simply unsafe to spend time next to a lighted stove.
Time has proven that the new type of sauna will never 'bury' the Russian classic.
Knowledge is power
Fundamentally different technologies
An authentic Russian steam room has reached thermal equilibrium once the steam session begins, i.e. all the internal surfaces have reached their same steady-state temperature. A sauna stove mainly heats the steam room and the people in it via radiant heat. There is no air flow inside the steam room. The solid stove creates the right conditions to gently and harmoniously heat the body; the absence of free air flow guarantees physical comfort and the red hot stove core produces the lightest steam possible. Light steam is emitted, the temperature in the steam room increases but there is no sensation of moisture in the air because the steam is so light.
Electric heaters. In this case the elements heated to a temperature of 300°С or more, transmit thermal energy into the air, which warms the steam room surfaces and the human bodies in it when it circulates inside the room. A significant temperature fluctuation (as much as 50°C) is noted between the floor and the ceiling, corresponding, according to GOST R ISO 7243-2007, to one of the signs of heat stress in harmful production environments. No light steam is produced. In an attempt to increase the WBGT the stove is often over-heated which results in drying out the air in the steam room. To mitigate the problem, an artificial steam generator is installed creating a source of heavy humidity. The maximum measurement that can be achieved with this type of gadget is WBGT 35°C - an uncomfortable condition to say the least.
It is possible to create a little bit of heaven in a steam room when the WBGT value is around 55° c. In these conditions, everyone is happy and the guests clap in approval;
WBGT 55°C can be achieved by installing a traditional, authentic, masonry sauna stove. This kind of stove guarantees light steam, soft heat, no air flow in the steam room, and excludes the likelihood of experiencing any discomfort during the steam session.
No other 'heating device' can create these conditions although they are quite capable of causing harm to the visitors to the steam room.