At the heart of every sauna, stones turn fire into a soothing embrace. Heated by the flames, they absorb and store energy, releasing it as a gentle, consistent heat when water, or löyly, is poured over them. Selected for their durability and strength, these robust igneous rocks provide the ideal balance of heat and ambiance, elevating each sauna session into a timeless and grounding ritual.
In Finnish public saunas, the stones are subjected to high temperatures daily. This frequent heat exposure gradually causes the stones to become brittle, diminishing their capacity to efficiently retain and conduct heat. As a result, more resources are required to maintain optimal sauna temperatures, necessitating the replacement of sauna stones every six months or even sooner in some cases. This heating process plays a vital role in the development of our materials, as it weakens the stones in a distinctive way that cannot be replicated by other means.
Material
The Sauna Stone Lab has innovatively developed a range of geopolymer materials utilizing discarded sauna stones, with some formulations incorporating up to 80% recycled content. Geopolymers are ceramic-like mineral polymers produced at low temperatures, typically below 100°C. This process enables the chemical bonding of mineral components, offering a sustainable solution to integrate local, natural, and industrial mineral waste. Recent research highlights that geopolymer-based materials contribute to 12 of the 17 United Nations Sustainable Development Goals (SDGs), underscoring their significant potential for environmental and social impact.
Sauna Stone Geopolymer material samples.
The story behind Sauna Stone Lab
A video by Yatofu Creatives and Mark Vicuña for the Habitare 2024 theme exhibition