More than 100 years of fireplace expertise

NunnaUuni’s own Mammutti soapstone deposit* and our experience-based skills in building soapstone fireplaces ensure that the fireplace building traditions of Nunnanlahti will stay alive and well long into the future.

This unique soapstone deposit*, which provides the perfect material for high-quality fire chambers, was discovered by the father and grandfather of NunnaUuni founder Juhani Lehikoinen – both fireplace masters themselves. What they ingeniously realised was that the type of soapstone in this particular deposit was different from that found in all of the area’s numerous other deposits, which had become known for providing easily workable building material. This highly heat-resistant type of soapstone proved to be an excellent fireplace material.

The strongly oriented and highly heat-resistant Mammutti soapstone is an exceptional natural stone. Geological research has proved its uniqueness.

The fire chambers and internal structures of heat-storing NunnaUuni fireplaces are made of this unique type of soapstone, which we call Mammutti soapstone. We only use soapstone from the company’s own soapstone deposit.

Its excellent thermal conductivity, outstanding heat storage capacity and superior heat resistance characteristics make the Mammutti type of soapstone the supreme source of comfortable warmth.

The fire chamber is the heart of a fireplace

Science has since proven what fireplace masters already knew more than a century ago. The best material for the fire chamber, the most vital part of the fireplace, is type of soapstone consisting of fine-grained magnesite and a combination of schistose and foliated, flaky talc formed under intense geologic pressure.

The surface of the fire chamber stone shown in the picture has turned light brown with use. Magnesium carbonate present in the soapstone surface converts to periclase (MgO) at temperatures exceeding 520 ºC. This periclase and the soapstone’s talc are then sintered together creating an extremely hard burning chamber surface.

In the high temperature conditions of the fire chamber, the surface of this type of soapstone converts into a hard talc-periclase layer that conducts heat extremely well. The layer is recognisable by a characteristic brownish colouration of the fire chamber surface. This kind of all-soapstone fire chamber stores a vast amount of heat quickly, and lasts for decades.

NunnaUuni fireplaces are built from the uniform, oriented and natural Mammutti type of soapstone. Mammutti soapstone conducts heat in the direction of the foliation at ten times1 the speed of conduction in ceramic bricks. This ensures that heat is captured and stored efficiently. NunnaUuni all-soapstone fire chambers do not require insulating protective plates or cast structures.

NunnaUuni is also an environmentally sustainable choice. Burning wood in a high temperature makes clean burning possible. Read more about the patented Golden Fire wood burning method.

* Name of mining concession: Nunnanlahti No. 3159
1) Alakangas, E. 1992. Taloustulisijojen käyttö. Building Information Ltd.