You can not show indifference to your own health and the health of close people by laying stones of unknown origin in the oven. After all, their chemical and physical properties can be completely insecure.
There are cases when stones, for example, recruited simply on the river bank, when heated in baths and saunas, radioactive substances or sulfur compounds were isolated, thus poisoning the human body. In addition, stones that are unusable for use in baths often crack from high temperatures, and if they get water, they can "shoot" and seriously injure the body with a sharp fragment.
How can I check the quality of the sauna stove?
Even a cursory external examination will allow you to determine if the stones for the bath have visible cracks. You can hit a stone against a stone, checking them, thus, on the strength. A more thorough examination of bath stones can be arranged by heating them in a fire and then placing them in cold water. If the stone does not burst, then the check has passed.
How to properly place stones in a sauna oven?
Follow when laying stones to the principle: the largest - at the bottom, the rest - at the top. Do not go wrong!
By the way, our advice to thrifty lovers of bathing procedures: you can save a substantial amount of money if you use an inexpensive breed as the main filling of the furnace, but on top of it lay the one that you like (regardless of the price).