Stone in the heater of steam sauna "produces" steam from water poured on it. For this, stone should be glowing (280-600 degrees). Generally, there are two dominant methods of stone’s glowing in furnaces or heaters:
Direct glowing - when the stones are heated by the burning fire and smoke.
Indirect glowing - when the stones are heated by the metal body of the heater or electric heating elements.
The stone‘s shape, size and the type depends on the way of the glowing of stone. Metallic furnaces heat stones by the corps boards, so stones should be set down not more than in two layers from the heated surface. The stones should be large - about the size of a fist (10-15 cm). They are well heated by metal and accumulate enough heat for steam.
In electric heaters stones glow by electric heating elements, which are located in a tank designed for stones, in a short distance from each other. This ensures even heating of the stones. In this case it is better to use smaller stones - from 5 to 7 cm.
Stones, placed in the heater, should be thoroughly rinsed. Their location in the heater is also very important for the qualitative sauna bathing. If you put the stones too close to each other, it may lead to the fact that the desired temperature will not be reached in the sauna because the air, with its heavy moving between the sauna stones, will disturb the process of firing the heater. It is better to place the stones in freely way, not too close and not too sparsely; pile of stones on the heater should also not be significant. Properly placed stones in the sauna heater will provide good air circulation and speed up the process of heating the sauna room.
Sauna stones are recommended to be changed once a year, but if the sauna is for commercial purpose, you should review them regularly. There is no need to change all the stones, throwing them away. Simply remove the stones from the heater and clean it, make sure that stones do not crumble away, if they are firm enough then wash them and put back in the heater. The missing amount of stones fill with new ones.
Recommended types of stones for the sauna - jadeite, soapstone, raspberry quartzite, white quartzite, ceramic stones, olivine diabase.
Jadeite - a semiprecious stone, because of its physical and therapeutic properties is very suitable for the sauna. Stone is firm enough, its corners are not sharp, it is not fissile, has inconsiderable absorption of water. Such a stone gives an easy, gentle and small steam in sauna. Its world's resources are limited, the stone does not react with acids, cleans the environmental air, is producible manually, there are no resources of such stone in Europe. Stone emits silicic acid (having analgesic, anti-toxic, antiphlogistic effects), very clean, has a lot of useful minerals for human organism. It is believed that because of its structural properties and chemical composition of jadeite, the stone has healing features - strengthens the nervous system, normalizes the arterial blood pressure, softens the walls of blood vessels, improves blood composition, strengthens male potency, the work of kidneys and the urinary tract.
Soapstone (talkochlorit) - stone, which consists of hard and soft minerals that are open to treatment. During the formation, the particles of talc grew into magnetism, so they are combined by a very strong connection, in such way forming an unbroken hard mass of stones. Soapstone is resistant to high temperatures, has very good thermal conductivity and has unique properties of well heat accumulation. So since ancient times it is known as a very suitable material for a sauna. The steam, coming from these stones, is very similar to the steam generated from the jadeite stone.
Raspberry quartzite - in other words - porphyry, due to its unique physical and mechanical properties is the most durable stone, used in all kinds of baths and saunas. Raspberry quartzite, due to its high density and low heat transmission, forms a gentle steam in sauna. It is believed that the raspberry quartzite regulates blood pressure, relieves back pain.