What Is Löyly? The Part of Sauna That a Thermometer Misses

Löyly (roughly pronounced LOW-lu, with a Finnish vowel sound English does not reproduce exactly) is the steam and wave of felt heat created when water is thrown on hot sauna stones. The word also describes the quality or character of a sauna's heat. Good löyly is clean, enveloping and controllable—not a sharp blast that scorches the face.

What happens when water hits the stones

Water vaporizes, mixes with the hot air and moves through the room. When the ceiling, benches, heater and ventilation are well arranged, the warm humid wave travels across the ceiling and descends over bathers. That is why löyly geometry matters.

The visible cloud near the ladle is condensed mist; water vapour itself is invisible. What skin feels is a sudden change in heat transfer as moisture condenses and the humid air moves.

What good löyly feels like

It reaches the whole body, not only the head.
It builds and fades rather than striking like a dry blast.
Bathers can control intensity with small additions of water.
The air remains fresh enough to breathe comfortably.
Stones recover between throws instead of leaving water to run through.

Poor löyly can come from cool or degraded stones, too little stone mass, low benches, a trapped ceiling pocket, harsh radiant exposure or an air path that misses bathers.

Löyly is social

Ask before throwing a large amount of water in a shared sauna. Start small. The person nearest the heater does not get to decide the dose for everyone.

Frequently asked questions

Is löyly just steam?

Physically it involves vapour and humid heat, but in Finnish sauna culture the word also carries the quality and atmosphere of the heat.

Can an electric sauna make löyly?

Yes. A proper electric sauna heater is designed for water on heated stones, as directed by its manual.