The use of stones dates back to 3,500 BC. Archaeologists from the University of Reading, led by Jim Leary, found the remains of a small building that once had a large fit pit at its center. Something was exciting about this fire pit, though. The ground had been scorched beneath it, and fragments of stones showed they had been heated to very high temperatures. However, the archaeologists could only find burning materials in a second fire pit outside the building. This indicated that the rocks were heated outside then carried inside. This would have provided plenty of warmth inside a small building. They concluded that the stones were used for some sort of primitive sauna.
Types of rocks
There are three main types of rocks: sedimentary, metamorphic, and igneous. Igneous rocks are also commonly called volcanic rocks, although these are an additional subcategory.
The first two categories — sedimentary and metamorphic — should not be used in a sauna as they're not dense enough to retain enough heat. They are also porous, so they may contain moisture, which leads to cracking or exploding in high heat.
Sauna rocks should instead be igneous rocks, which generally tend to be dense and non-porous. There are some exceptions for igneous rocks that don't make good sauna rocks since they don't have the typical characteristics. For example, obsidian is too smooth while pumice is too light.
What size of rocks do saunas use?
The rocks for your sauna should not be bigger than a medium-sized potato nor bigger than a golf ball. If the stones are too small, they will heat up too quickly, and if the rocks are too big, they will take too long to heat up.
Do sauna rocks need to be replaced?
Sauna rocks need to be replaced according to how much you use your sauna. A good rule of thumb is that if you use your sauna once a week, replace your rocks once a year, twice a week, twice a year, and so on.
You can re-arrange the position of your rocks before opting to replace them. This will improve air circulation and rotate which stones are at the bottom of the pile since the ones closest to the heater will likely disintegrate faster than the rest.
How much water should I pour onto my sauna rocks?
It might be tempting to pour large amounts of water onto your sauna rocks to get a massive burst of steam, but this is not recommended, as too much steam can blister your skin!
Finding the right amount of water is pretty much an art. The Finns even have a word specifically for this action; that word is Löyly. This word means "the steam that rises from the sauna stove." Splashing cold water on the rocks will improve your Löyly experience (since you'll receive a lot more steam), but if you do it too often or with too much water, you risk overcooling the rocks or overflowing your sauna heater. You should also know that the cooler the water, the more steam the heater will create. It may sound very complicated, but believe us, once you master this art, you'll have the most relaxing and refreshing sessions.
It would be best to add about 3-5 oz per session. A session means the uninterrupted time you spend in the sauna. This could be anywhere between 5 to 20 minutes. Let's say you are doing three sessions of 5 minutes each, and take 5 minutes to cool off in between each session. Then every time you go back in, you can pour more water to achieve the desired amount of steam. We recommend using a wooden bucket and ladle to achieve better results.
Finding the right sauna rocks goes hand in hand with knowing how to utilize them to their maximum potential. Practice different water temperatures and amounts until you find the most suitable temperature and moisture for you.
At Scandia MFG, sauna rocks are offered in various colors and textures, allowing you to customize your sauna to fit your specific style and needs.