Sauna stones are heat-retaining rocks used in traditional and electric sauna heaters to store thermal energy and produce steam when water is poured over them. As a core element of the sauna experience, these stones not only regulate heat but also influence the intensity, humidity, and quality of the steam (löyly). Choosing the right type and arrangement of sauna stones is essential for achieving a balanced, comfortable, and safe sauna environment.
Purpose and Function of Sauna Stones
1. Heat Retention and Release
Sauna stones absorb and store the heat generated by the heater, releasing it slowly to warm the surrounding air. This consistent thermal radiation creates the signature dry, enveloping heat of the sauna.
2. Steam Production
When water is ladled onto hot stones, it instantly vaporizes, producing löyly—a burst of hot, moist steam that enhances the sauna's sensory experience and improves respiratory comfort.
Types of Sauna Stones
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Peridotite: A common volcanic stone with high density and excellent heat storage
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Olivine diabase: Durable and crack-resistant, known for long heat retention
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Gabbro: A dense igneous rock ideal for intense heat cycles
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Ceramic-coated stones: Used in some electric heaters for faster warm-up and easier maintenance
How to Choose Sauna Stones
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Size variety: Use a mix of large and small stones—larger stones retain heat, while smaller ones help produce steam quickly
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Rough surface: Textured stones hold water better and distribute heat more evenly
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Natural material: Avoid artificial or chemically treated rocks, which can emit fumes when heated
Proper Placement in the Heater
- Arrange loosely to allow air circulation between stones
- Place larger stones at the bottom for heat storage
- Layer smaller stones on top for quicker steam response
- Do not overfill—the heater needs airflow to function safely
Maintenance and Replacement
- Inspect stones every 3–6 months for cracks or dust buildup
- Rinse or brush stones to remove soot and debris
- Replace crumbling or discolored stones regularly to maintain performance
- Follow the heater manufacturer’s recommendations on stone quantity and type
Safety Tips
- Use only sauna-rated stones—never use river rocks or unknown materials
- Ensure stones are completely dry before heating to avoid steam explosions
- Wear protective gloves when arranging or replacing hot stones
Conclusion
Sauna stones are more than just functional—they're central to the sensory and therapeutic power of the sauna. By storing and releasing heat effectively, they create the signature warmth and steam that define the sauna ritual. Choosing the right stones and caring for them properly ensures a safe, enjoyable, and deeply rejuvenating experience every time you enter the sauna.
