Why saunas need stones

April — the (unofficial) Month of Sauna Stones

You might think of a sauna as a room lined with clear wood paneling and tiers of benches — or a room that is heated to (uncomfortably) high temps. While both are true, neither defines the core of a sauna.

Actually, the sauna is the container for hot stones. Its stove is meant not to heat the sauna but the rocks. Surprised??

Without its stones, sitting in a sauna would feel more like being in a toaster. Rocks store heat and distribute it evenly, keeping the sauna hot longer. Plus the rocks provide surfaces for water to hit and make momentary steam — the löyly. The hotter the stones, the faster the water evaporates.

The oldest Finnish saunas, smoke saunas or savusaunas, needed the heat-retaining capacity of massive stones because people hadn’t yet invented a method for continuous heating. A fire lit underneath an arch of huge rocks burned for hours, all the while heating those rocks — sometimes to red-hot. The radiant heat lasted for many more hours, through several rounds of bathers. 

This photo of the savusauna in the Cokato Historical Society Museum of Cokato, Minnesota, gives an idea of the size of rocks that were sometimes used. 

In modern saunas with electric stoves, that energy-storing capacity is less critical. The heating element stays on — to heat the sauna and during the bath. We don’t have to “save heat” for the next bather, as Finns did long ago. But the heat radiated by the rocks makes our saunas so much more pleasant.

Next discussion: Why rocks were chosen, by legend, by sentiment and any other reason.  

Nikki